AnatomyandPhysiology-IAG(1)
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 1: Levels of Organization
Chapter 1: An Introduction to the Human Body
Interactive Link Questions
1. View this animation (http://openstaxcollege.org/l/metabolic) to learn more about metabolic processes. What kind of catabolism occurs in the heart?
Answer
Fatty acid catabolism.
2. Water concentration in the body is critical for proper functioning. A person’s body retains very tight control on water levels without conscious control by the person. Watch this video (http://openstaxcollege.org/l/H2Ocon) to learn more about water concentration in the body. Which organ has primary control over the amount of water in the body?
Answer
The kidneys.
3. A CT or CAT scan relies on a circling scanner that revolves around the patient’s body. Watch this video (http://openstaxcollege.org/l/CATscan) to learn more about CT and CAT scans. What type of radiation does a CT scanner use?
Answer
X-rays.
4. A patient undergoing an MRI is surrounded by a tube-shaped scanner. Watch this video (http://openstaxcollege.org/l/MRI) to learn more about MRIs. What is the function of magnets in an MRI?
Answer
The magnets induce tissue to emit radio signals that can show differences between different types of tissue.
5. PET relies on radioactive substances administered several minutes before the scan. Watch this video (http://openstaxcollege.org/l/PET) to learn more about PET. How is PET used in chemotherapy?
Answer
PET scans can indicate how patients are responding to chemotherapy
Review Questions
6. Which of the following specialties might focus on studying all of the structures of the ankle and foot?
Answer
C. regional anatomy
7. A scientist wants to study how the body uses foods and fluids during a marathon run. This scientist is most likely a(n) ________.
Answer A. exercise physiologist
8. The smallest independently functioning biological unit of an organism is a(n) ________.
Answer
A. cell 9. A collection of similar tissues that performs a specific function is an ________.
Answer
A. organ
OpenStax Anatomy & Physiology Instructor Answer Guide
10. The body system responsible for structural support and movement is the ________.
Answer
D. skeletal system
11. Metabolism can be defined as the ________.
Answer
D. sum of all chemical reactions in an organism
12. Adenosine triphosphate (ATP) is an important molecule because it ________.
Answer
C. stores energy for use by body cells 13. Cancer cells can be characterized as “generic” cells that perform no specialized body function. Thus cancer cells lack ________.
Answer
A. differentiation
14. Humans have the most urgent need for a continuous supply of ________.
Answer
C. oxygen
15. Which of the following statements about nutrients is true?
Answer
A. All classes of nutrients are essential to human survival.
16. C.J. is stuck in her car during a bitterly cold blizzard. Her body responds to the cold by ________.
Answer
C. breaking down stored energy
17. After you eat lunch, nerve cells in your stomach respond to the distension (the stimulus) resulting from the food. They relay this information to ________.
Answer
A. a control center
18. Stimulation of the heat-loss center causes ________.
Answer
C. sweat glands to increase their output
19. Which of the following is an example of a normal physiologic process that uses a positive feedback loop?
Answer
B. childbirth
20. What is the position of the body when it is in the “normal anatomical position?”
Answer
D. None of the above
21. To make a banana split, you halve a banana into two long, thin, right and left sides along the ________.
Answer
C. midsagittal plane 22. The lumbar region is ________.
Answer
D. superior to the popliteal region 23. The heart is within the ________.
Answer
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B. mediastinum
24. In 1901, Wilhelm Röntgen was the first person to win the Nobel Prize for physics. For what discovery did he win?
Answer
D. X-rays
25. Which of the following imaging techniques would be best to use to study the uptake of nutrients by rapidly multiplying cancer cells?
Answer
C. PET
26. Which of the following imaging studies can be used most safely during pregnancy?
Answer
C. ultrasound
27. What are two major disadvantages of MRI scans?
Answer
B. high cost and the need for shielding from the magnetic signals Critical Thinking Questions
28. Name at least three reasons to study anatomy and physiology.
Answer
An understanding of anatomy and physiology is essential for any career in the health professions.
It can also help you make choices that promote your health, respond appropriately to signs of illness, make sense of health-related news, and help you in your roles as a parent, spouse, partner, friend, colleague, and caregiver.
29. For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
Answer
A student would more readily appreciate the structures revealed in the dissection. Even though the student has not yet studied the workings of the heart and blood vessels in her class, she has experienced her heart beating every moment of her life, has probably felt her pulse, and likely has at least a basic understanding of the role of the heart in pumping blood throughout her body. This understanding of the heart’s function (physiology) would support her study of the heart’s form (anatomy).
30. Name the six levels of organization of the human body
Answer
Chemical, cellular, tissue, organ, organ system, organism.
31. The female ovaries and the male testes are a part of which body system? Can these organs be members of more than one organ system? Why or why not?
Answer
The female ovaries and the male testes are parts of the reproductive system. But they also secrete
hormones, as does the endocrine system, therefore ovaries and testes function within both the endocrine and reproductive systems.
32. Explain why the smell of smoke when you are sitting at a campfire does not trigger alarm, but the smell of smoke in your residence hall does.
Answer
OpenStax Anatomy & Physiology Instructor Answer Guide
When you are sitting at a campfire, your sense of smell adapts to the smell of smoke. Only if that
smell were to suddenly and dramatically intensify would you be likely to notice and respond. In contrast, the smell of even a trace of smoke would be new and highly unusual in your residence hall, and would be perceived as danger.
33. Identify three different ways that growth can occur in the human body.
Answer
Growth can occur by increasing the number of existing cells, increasing the size of existing cells,
or increasing the amount of non-cellular material around cells.
34. When you open a bottle of sparkling water, the carbon dioxide gas in the bottle form bubbles.
If the bottle is left open, the water will eventually “go flat.” Explain these phenomena in terms of
atmospheric pressure.
Answer
In a sealed bottle of sparkling water, carbon dioxide gas is kept dissolved in the water under a very high pressure. When you open the bottle, the pressure of the gas above the liquid changes from artificially high to normal atmospheric pressure. The dissolved carbon dioxide gas expands,
and rises in bubbles to the surface. When a bottle of sparkling water is left open, it eventually goes flat because its gases continue to move out of solution until the pressure in the water is approximately equal to atmospheric pressure.
35. On his midsummer trek through the desert, Josh ran out of water. Why is this particularly dangerous?
Answer
The primary way that the body responds to high environmental heat is by sweating; however, sweating requires water, which comes from body fluids, including blood plasma. If Josh becomes dehydrated, he will be unable to sweat adequately to cool his body, and he will be at risk for heat stroke as his blood pressure drops too much from the loss of water from the blood plasma.
36. Identify the four components of a negative feedback loop and explain what would happen if secretion of a body chemical controlled by a negative feedback system became too great.
Answer
The four components of a negative feedback loop are: stimulus, sensor, control center, and effector. If too great a quantity of the chemical were excreted, sensors would activate a control center, which would in turn activate an effector. In this case, the effector (the secreting cells) would be adjusted downward.
37. What regulatory processes would your body use if you were trapped by a blizzard in an unheated, uninsulated cabin in the woods?
Answer
Any prolonged exposure to extreme cold would activate the brain’s heat-gain center. This would reduce blood flow to your skin, and shunt blood returning from your limbs away from the digits and into a network of deep veins. Your brain’s heat-gain center would also increase your muscle contraction, causing you to shiver. This increases the energy consumption of skeletal muscle and generates more heat. Your body would also produce thyroid hormone and epinephrine, chemicals
that promote increased metabolism and heat production.
38. In which direction would an MRI scanner move to produce sequential images of the body in the frontal plane, and in which direction would an MRI scanner move to produce sequential images of the body in the sagittal plane?
Answer
OpenStax Anatomy & Physiology Instructor Answer Guide
If the body were supine or prone, the MRI scanner would move from top to bottom to produce frontal sections, which would divide the body into anterior and posterior portions, as in “cutting”
a deck of cards. Again, if the body were supine or prone, to produce sagittal sections, the scanner
would move from left to right or from right to left to divide the body lengthwise into left and right portions. 39. If a bullet were to penetrate a lung, which three anterior thoracic body cavities would it enter,
and which layer of the serous membrane would it encounter first? Answer
The bullet would enter the ventral, thoracic, and pleural cavities, and it would encounter the parietal layer of serous membrane first.
40. Which medical imaging technique is most dangerous to use repeatedly, and why?
Answer
CT scanning subjects patients to much higher levels of radiation than X-rays, and should not be performed repeatedly.
41. Explain why ultrasound imaging is the technique of choice for studying fetal growth and development.
Answer
Ultrasonography does not expose a mother or fetus to radiation, to radiopharmaceuticals, or to magnetic fields. At this time, there are no known medical risks of ultrasonography.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 1: Levels of Organization
Chapter 2: The Chemical Level of Organization
Interactive Link Questions
1. Visit this website (http://openstaxcollege.org/l/ptable) to view the periodic table. In the periodic table of the elements, elements in a single column have the same number of electrons that can participate in a chemical reaction. These electrons are known as “valence electrons.” For
example, the elements in the first column all have a single valence electron—an electron that can
be “donated” in a chemical reaction with another atom. What is the meaning of a mass number shown in parentheses?
Answer
The mass number is the total number of protons and neutrons in the nucleus of an atom.
2. Visit this website (http://openstaxcollege.org/l/electenergy) to learn about electrical energy and the attraction/repulsion of charges. What happens to the charged electroscope when a conductor is moved between its plastic sheets, and why?
Answer
The plastic sheets jump to the nail (the conductor), because the conductor takes on electrons from the electroscope, reducing the repellant force of the two sheets.
3. Watch this video (http://openstaxcollege.org/l/disaccharide) to observe the formation of a disaccharide. What happens when water encounters a glycosidic bond?
Answer
The water hydrolyses, or breaks, the glycosidic bond, forming two monosaccharides.
Review Questions
4. Together, just four elements make up more than 95 percent of the body’s mass. These include ________.
Answer
D. oxygen, carbon, hydrogen, and nitrogen
5. The smallest unit of an element that still retains the distinctive behavior of that element is an ________.
Answer
B. atom
6. The characteristic that gives an element its distinctive properties is its number of ________.
Answer
A. protons
7. On the periodic table of the elements, mercury (Hg) has an atomic number of 80 and a mass number of 200.59. It has seven stable isotopes. The most abundant of these probably have ________.
Answer
C. more than 80 neutrons each
8. Nitrogen has an atomic number of seven. How many electron shells does it likely have?
Answer
B. two
9. Which of the following is a molecule, but not a compound?
Answer
C. H
2
OpenStax Anatomy & Physiology Instructor Answer Guide
10. A molecule of ammonia contains one atom of nitrogen and three atoms of hydrogen. These are linked with ________.
Answer
C. polar covalent bonds
11. When an atom donates an electron to another atom, it becomes
Answer
A. an ion
12. A substance formed of crystals of equal numbers of cations and anions held together by ionic
bonds is called a(n) ________.
Answer
B. salt
13. Which of the following statements about chemical bonds is true?
Answer
A. Covalent bonds are stronger than ionic bonds.
14. The energy stored in a foot of snow on a steep roof is ________.
Answer
A. potential energy
15. The bonding of calcium, phosphorus, and other elements produces mineral crystals that are found in bone. This is an example of a(n) ________ reaction.
Answer
B. synthesis
16. AB → A + B is a general notation for a(n) ________ reaction.
Answer
C. decomposition
17. ________ reactions release energy.
Answer
D. Catabolic, exergonic, and decomposition
18. Which of the following combinations of atoms is most likely to result in a chemical reaction?
Answer
A. hydrogen and hydrogen
19. Chewing a bite of bread mixes it with saliva and facilitates its chemical breakdown. This is most likely due to the fact that ________.
Answer
D. saliva contains enzymes
20. CH
4
is methane. This compound is ________.
Answer
B. organic
21. Which of the following is most likely to be found evenly distributed in water in a homogeneous solution?
Answer
A. sodium ions and chloride ions
22. Jenny mixes up a batch of pancake batter, then stirs in some chocolate chips. As she is waiting for the first few pancakes to cook, she notices the chocolate chips sinking to the bottom of the clear glass mixing bowl. The chocolate-chip batter is an example of a ________.
Answer
D. suspension
OpenStax Anatomy & Physiology Instructor Answer Guide
23. A substance dissociates into K
+
and Cl
-
in solution. The substance is a(n) ________.
Answer
C. salt
24. Ty is three years old and as a result of a “stomach bug” has been vomiting for about 24 hours. His blood pH is 7.48. What does this mean?
Answer
B. Ty’s blood is slightly alkaline.
25. C
6
H
12
O
6
is the chemical formula for a ________.
Answer
C. hexose monosaccharide
26. What organic compound do brain cells primarily rely on for fuel?
Answer
A. glucose
27. Which of the following is a functional group that is part of a building block of proteins?
Answer
C. amino
28. A pentose sugar is a part of the monomer used to build which type of macromolecule?
Answer
B. nucleic acids
29. A phospholipid ________.
Answer
A. has both polar and nonpolar regions
30. In DNA, nucleotide bonding forms a compound with a characteristic shape known as a(n) ________.
Answer
D. double helix
31. Uracil ________.
Answer
D. all of the above (contains nitrogen, is a pyrimidine, is found in RNA)
32. The ability of an enzyme’s active sites to bind only substrates of compatible shape and charge is known as ________.
Answer
B. specificity
Critical Thinking Questions
33. The most abundant elements in the foods and beverages you consume are oxygen, carbon, hydrogen, and nitrogen. Why might having these elements in consumables be useful?
Answer
These four elements—oxygen, carbon, hydrogen, and nitrogen—together make up more than 95 percent of the mass of the human body, and the body cannot make elements, so it is helpful to have them in consumables.
34. Oxygen, whose atomic number is eight, has three stable isotopes: 16
O, 17
O, and 18
O. Explain what this means in terms of the number of protons and neutrons.
Answer
Oxygen has eight protons. In its most abundant stable form, it has eight neutrons, too, for a mass number of 16. In contrast, 17
O has nine neutrons, and 18
O has 10 neutrons.
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35. Magnesium is an important element in the human body, especially in bones. Magnesium’s atomic number is 12. Is it stable or reactive? Why? If it were to react with another atom, would it
be more likely to accept or to donate one or more electrons?
Answer
Magnesium’s 12 electrons are distributed as follows: two in the first shell, eight in the second shell, and two in its valence shell. According to the octet rule, magnesium is unstable (reactive) because its valence shell has just two electrons. It is therefore likely to participate in chemical reactions in which it donates two electrons.
36. Explain why CH
4
is one of the most common molecules found in nature. Are the bonds between the atoms ionic or covalent?
Answer
A carbon atom has four electrons in its valence shell. According to the octet rule, it will readily participate in chemical reactions that result in its valence shell having eight electrons. Hydrogen, with one electron, will complete its valence shell with two. Electron sharing between an atom of carbon and four atoms of hydrogen meets the requirements of all atoms. The bonds are covalent because the electrons are shared: although hydrogen often participates in ionic bonds, carbon does not because it is highly unlikely to donate or accept four electrons.
37. In a hurry one day, you merely rinse your lunch dishes with water. As you are drying your salad bowl, you notice that it still has an oily film. Why was the water alone not effective in cleaning the bowl?
Answer
Water is a polar molecule. It has a region of weakly positive charge and a region of weakly negative charge. These regions are attracted to ions as well as to other polar molecules. Oils are nonpolar, and are repelled by water.
38. Could two atoms of oxygen engage in ionic bonding? Why or why not?
Answer
Identical atoms have identical electronegativity and cannot form ionic bonds. Oxygen, for example, has six electrons in its valence shell. Neither donating nor accepting the valence shell electrons of the other will result in the oxygen atoms completing their valence shells. Two atoms of the same element always form covalent bonds.
39. AB + CD → AD + BE Is this a legitimate example of an exchange reaction? Why or why not?
Answer
It is not. An exchange reaction might be AB + CD → AC + BD or AB + CD → AD + BC. In all chemical reactions, including exchange reactions, the components of the reactants are identical to
the components of the products. A component present among the reactants cannot disappear, nor can a component not present in the reactants suddenly appear in the products.
40. When you do a load of laundry, why do you not just drop a bar of soap into the washing machine? In other words, why is laundry detergent sold as a liquid or powder?
Answer
Recall that the greater the surface area of the reactants, the more quickly and easily they will interact. It takes energy to separate particles of a substance. Powder and liquid laundry detergents, with relatively more surface area per unit, can quickly dissolve into their reactive components when added to the water.
41. The pH of lemon juice is 2, and the pH of orange juice is 4. Which of these is more acidic, and by how much? What does this mean?
OpenStax Anatomy & Physiology Instructor Answer Guide
Answer
Lemon juice is one hundred times more acidic than orange juice. This means that lemon juice has a one hundred-fold greater concentration of hydrogen ions.
42. During a party, Eli loses a bet and is forced to drink a bottle of lemon juice. Not long thereafter, he begins complaining of having difficulty breathing, and his friends take him to the local emergency room. There, he is given an intravenous solution of bicarbonate. Why?
Answer
Lemon juice, like any acid, releases hydrogen ions in solution. As excessive H
+
enters the digestive tract and is absorbed into blood, Eli’s blood pH falls below 7.35. Recall that bicarbonate is a buffer, a weak base that accepts hydrogen ions. By administering bicarbonate intravenously, the emergency department physician helps raise Eli’s blood pH back toward neutral.
43. If the disaccharide maltose is formed from two glucose monosaccharides, which are hexose sugars, how many atoms of carbon, hydrogen, and oxygen does maltose contain and why?
Answer
Maltose contains 12 atoms of carbon, but only 22 atoms of hydrogen and 11 atoms of oxygen, because a molecule of water is removed during its formation via dehydration synthesis.
44. Once dietary fats are digested and absorbed, why can they not be released directly into the bloodstream?
Answer
All lipids are hydrophobic and unable to dissolve in the watery environment of blood. They are packaged into lipoproteins, whose outer protein envelope enables them to transport fats in the bloodstream.
OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 1: Levels of Organization
Chapter 3: The Cellular Level of Organization
Interactive Link Questions
1. Visit this link (http://openstaxcollege.org/l/diffusion) to see diffusion and how it is propelled by the kinetic energy of molecules in solution. How does temperature affect diffusion rate, and why?
Answer
Higher temperatures speed up diffusion because molecules have more kinetic energy at higher temperatures.
2. Watch this video (http://openstaxcollege.org/l/endomembrane1) to learn about the endomembrane system, which includes the rough and smooth ER and the Golgi body as well as lysosomes and vesicles. What is the primary role of the endomembrane system?
Answer
Processing, packaging, and moving materials manufactured by the cell.
3. Watch this video (http://openstaxcollege.org/l/DNArep) to learn about DNA replication. DNA replication proceeds simultaneously at several sites on the same molecule. What separates the base pair at the start of DNA replication?
Answer
an enzyme
4. Watch this video (http://openstaxcollege.org/l/ribosome) to learn about ribosomes. The ribosome binds to the mRNA molecule to start translation of its code into a protein. What happens to the small and large ribosomal subunits at the end of translation?
Answer
They separate and move and are free to join translation of other segments of mRNA.
5. Visit this link (http://openstaxcollege.org/l/mitosis) to learn about mitosis. Mitosis results in two identical diploid cells. What structures form during prophase?
Answer
the spindle
Review Questions
6. Because they are embedded within the membrane, ion channels are examples of ________.
Answer
B. integral proteins
7. The diffusion of substances within a solution tends to move those substances ________ their ________ gradient.
Answer
D. down; concentration
8. Ion pumps and phagocytosis are both examples of ________.
Answer
C. active transport
9. Choose the answer that best completes the following analogy: Diffusion is to ________ as endocytosis is to ________.
Answer
B. osmosis; pinocytosis
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10. Choose the term that best completes the following analogy: Cytoplasm is to cytosol as a swimming pool containing chlorine and flotation toys is to ________.
Answer
D. the water
11. The rough ER has its name due to what associated structures?
Answer
B. ribosomes
12. Which of the following is a function of the rough ER?
Answer
A. production of proteins
13. Which of the following is a feature common to all three components of the cytoskeleton?
Answer
C. They are all polymers of protein subunits.
14. Which of the following organelles produces large quantities of ATP when both glucose and oxygen are available to the cell?
Answer
A. mitochondria
15. The nucleus and mitochondria share which of the following features?
Answer
B. a double cell membrane
16. Which of the following structures could be found within the nucleolus?
Answer
C. ribosomes
17. Which of the following sequences on a DNA molecule would be complementary to GCTTATAT?
Answer
C. CGAATATA
18. Place the following structures in order from least to most complex organization: chromatin, nucleosome, DNA, chromosome
Answer
A. DNA, nucleosome, chromatin, chromosome
19. Which of the following is part of the elongation step of DNA synthesis?
Answer
B. attaching complementary nucleotides to the template strand
20. Which of the following is not a difference between DNA and RNA?
Answer
C. DNA contains alternating sugar-phosphate molecules whereas RNA does not contain sugars
21. Transcription and translation take place in the ________ and ________, respectively.
Answer
A. nucleus; cytoplasm
22. How many “letters” of an RNA molecule, in sequence, does it take to provide the code for a single amino acid?
Answer
C. 3
23. Which of the following is not made out of RNA?
Answer
OpenStax Anatomy & Physiology Instructor Answer Guide
B. the ribosome
24. Which of the following phases is characterized by preparation for DNA synthesis?
Answer
B. G
1
25. A mutation in the gene for a cyclin protein might result in which of the following?
Answer
D. any of the above (a cell with additional genetic material than normal, cancer, a cell with less genetic material than normal)
26. What is a primary function of tumor suppressor genes?
Answer
B. stop certain cells from dividing
27. Arrange the following terms in order of increasing specialization: oligopotency, pleuripotency, unipotency, multipotency.
Answer
D. pleuripotency, multipotency, oligopotency, unipotency
28. Which type of stem cell gives rise to red and white blood cells?
Answer
C. hematopoietic
29. What multipotent stem cells from children sometimes banked by parents?
Answer
C. cells from the umbilical cord and from baby teeth
Critical Thinking Questions
30. What materials can easily diffuse through the lipid bilayer, and why?
Answer
Only materials that are relatively small and nonpolar can easily diffuse through the lipid bilayer. Large particles cannot fit in between the individual phospholipids that are packed together, and polar molecules are repelled by the hydrophobic/nonpolar lipids that line the inside of the bilayer.
31. Why is receptor-mediated endocytosis said to be more selective than phagocytosis or pinocytosis?
Answer
Receptor-mediated endocytosis is more selective because the substances that are brought into the
cell are the specific ligands that could bind to the receptors being endocytosed. Phagocytosis or pinocytosis, on the other hand, have no such receptor-ligand specificity, and bring in whatever materials happen to be close to the membrane when it is enveloped.
32. What do osmosis, diffusion, filtration, and the movement of ions away from like charge all have in common? In what way do they differ?
Answer
These four phenomena are similar in the sense that they describe the movement of substances down a particular type of gradient. Osmosis and diffusion involve the movement of water and other substances down their concentration gradients, respectively. Filtration describes the movement of particles down a pressure gradient, and the movement of ions away from like charge describes their movement down their electrical gradient.
33. Explain why the structure of the ER, mitochondria, and Golgi apparatus assist their respective functions.
OpenStax Anatomy & Physiology Instructor Answer Guide
Answer
The structure of the Golgi apparatus is suited to its function because it is a series of flattened membranous discs; substances are modified and packaged in sequential steps as they travel from one disc to the next. The structure of Golgi apparatus also involves a receiving face and a sending face, which organize cellular products as they enter and leave the Golgi apparatus. The ER and the mitochondria both have structural specializations that increase their surface area. In the mitochondria, the inner membrane is extensively folded, which increases surface area for ATP production. Likewise, the ER is elaborately wound throughout the cell, increasing its surface area for functions like lipid synthesis, Ca
++
storage, and protein synthesis. 34. Compare and contrast lysosomes with peroxisomes: name at least two similarities and one difference.
Answer
Peroxisomes and lysosomes are both cellular organelles bound by lipid bilayer membranes, and they both contain many enzymes. However, peroxisomes contain enzymes that detoxify substances by transferring hydrogen atoms and producing H
2
O
2
, whereas the enzymes in lysosomes function to break down and digest various unwanted materials.
35. Explain in your own words why DNA replication is said to be “semiconservative”?
Answer
DNA replication is said to be semiconservative because, after replication is complete, one of the two parent DNA strands makes up half of each new DNA molecule. The other half is a newly synthesized strand. Therefore, half (“semi”) of each daughter DNA molecule is from the parent molecule and half is a new molecule.
36. Why is it important that DNA replication take place before cell division? What would happen
if cell division of a body cell took place without DNA replication, or when DNA replication was incomplete?
Answer
During cell division, one cell divides to produce two new cells. In order for all of the cells in your body to maintain a full genome, each cell must replicate its DNA before it divides so that a full genome can be allotted to each of its offspring cells. If DNA replication did not take place fully, or at all, the offspring cells would be missing some or all of the genome. This could be disastrous if a cell was missing genes necessary for its function and health.
37. Briefly explain the similarities between transcription and DNA replication.
Answer
Transcription and DNA replication both involve the synthesis of nucleic acids. These processes share many common features—particularly, the similar processes of initiation, elongation, and termination. In both cases the DNA molecule must be untwisted and separated, and the coding (i.e., sense) strand will be used as a template. Also, polymerases serve to add nucleotides to the growing DNA or mRNA strand. Both processes are signaled to terminate when completed.
38. Contrast transcription and translation. Name at least three differences between the two processes.
Answer
Transcription is really a “copy” process and translation is really an “interpretation” process, because transcription involves copying the DNA message into a very similar RNA message whereas translation involves converting the RNA message into the very different amino acid message. The two processes also differ in their location: transcription occurs in the nucleus and translation in the cytoplasm. The mechanisms by which the two processes are performed are also
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completely different: transcription utilizes polymerase enzymes to build mRNA whereas translation utilizes different kinds of RNA to build protein.
39. What would happen if anaphase proceeded even though the sister chromatids were not properly attached to their respective microtubules and lined up at the metaphase plate?
Answer
One or both of the new daughter cells would accidently receive duplicate chromosomes and/or would be missing certain chromosomes.
40. What are cyclins and cyclin-dependent kinases, and how do they interact?
Answer
A cyclin is one of the primary classes of cell cycle control molecules, while a cyclin-dependent kinase (is one of a group of molecules that work together with cyclins to determine progression past cell checkpoints. By interacting with many additional molecules, these triggers push the cell cycle forward unless prevented from doing so by “stop” signals, if for some reason the cell is not
ready.
41. Explain how a transcription factor ultimately determines whether or not a protein will be present in a given cell?
Answer
Transcription factors bind to DNA and either promote or inhibit the transcription of a gene. If they promote the transcription of a particular gene, then that gene will be transcribed and the mRNA subsequently translated into protein. If gene transcription is inhibited, then there will be no way of synthesizing the gene’s corresponding protein.
42. Discuss two reasons why the therapeutic use of embryonic stem cells can present a problem.
Answer
Embryonic stem cells derive from human embryos, which are destroyed to obtain the cells. The destruction of human embryos is an ethical problem. And, the DNA in an embryonic stem cell would differ from the DNA of the person being treated, which could result in immune problems or rejected of tissue.
OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 1: Levels of Organization
Chapter 4: The Tissue Level of Organization
Interactive Link Questions
1. View this slideshow (http://openstaxcollege.org/l/stemcells) to learn more about stem cells. How do somatic stem cells differ from embryonic stem cells?
Answer
Most somatic stem cells give rise to only a few cell types.
2. Watch this video (http://openstaxcollege.org/l/etissues) to find out more about the anatomy of epithelial tissues. Where in the body would one find non-keratinizing stratified squamous epithelium?
Answer
The inside of the mouth, esophagus, vaginal canal, and anus.
3. Visit this link (http://openstaxcollege.org/l/10quiz) to test your connective tissue knowledge with this 10-question quiz. Can you name the 10 tissue types shown in the histology slides?
Answer
Click at the bottom of the quiz for the answers.
4. Watch this video (http://openstaxcollege.org/l/musctissue) to learn more about muscle tissue. In looking through a microscope how could you distinguish skeletal muscle tissue from smooth muscle?
Answer
Skeletal muscle cells are striated.
5. Follow this link (http://openstaxcollege.org/l/nobel) to learn more about nervous tissue. What are the main parts of a nerve cell?
Answer
Dendrites, cell body, and the axon.
6. Watch this video (http://openstaxcollege.org/l/healinghand) to see a hand heal. Over what period of time do you think these images were taken?
Answer
Approximately one month.
7. Watch this video (http://openstaxcollege.org/l/tumor) to learn more about tumors. What is a tumor?
Answer
A mass of cancer cells that continue to grow and divide.
Review Questions
8. Which of the following is not a type of tissue?
Answer
C. embryonic
9. The process by which a less specialized cell matures into a more specialized cell is called ________.
Answer
A. differentiation
10. Differentiated cells in a developing embryo derive from ________.
Answer
B. ectoderm, mesoderm, and endoderm
OpenStax Anatomy & Physiology Instructor Answer Guide
11. Which of the following lines the body cavities exposed to the external environment?
Answer
D. mucosa
12. In observing epithelial cells under a microscope, the cells are arranged in a single layer and look tall and narrow, and the nucleus is located close to the basal side of the cell. The specimen is what type of epithelial tissue?
Answer
A. columnar
13. Which of the following is the epithelial tissue that lines the interior of blood vessels?
Answer
C. simple squamous
14. Which type of epithelial tissue specializes in moving particles across its surface and is found in airways?
Answer
C. pseudostratified ciliated columnar
15. The ________ exocrine gland stores its secretion until the glandular cell ruptures, whereas the ________ gland releases its apical region and reforms.
Answer
A. holocrine; apocrine
16. Connective tissue is made of which three essential components?
Answer
B. cells, ground substance, and protein fibers
17. Under the microscope, a tissue specimen shows cells located in spaces scattered in a transparent background. This is probably ________.
Answer
D. hyaline cartilage
18. Which connective tissue specializes in storage of fat?
Answer
B. adipose tissue
19. Ligaments connect bones together and withstand a lot of stress. What type of connective tissue should you expect ligaments to contain?
Answer
C. dense regular connective tissue
20. In adults, new connective tissue cells originate from the ________.
Answer
B. mesenchyme
21. In bone, the main cells are ________.
Answer
D. osteocytes
22. Striations, cylindrical cells, and multiple nuclei are observed in ________.
Answer
A. skeletal muscle only
23. The cells of muscles, myocytes, develop from ________.
Answer
A. myoblasts
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24. Skeletal muscle is composed of very hard working cells. Which organelles do you expect to find in abundance in skeletal muscle cell?
Answer
D. mitochondria
25. The cells responsible for the transmission of the nerve impulse are ________.
Answer
A. neurons
26. The nerve impulse travels down a(n) ________, away from the cell body.
Answer
B. axon
27. Which of the following central nervous system cells regulate ions, regulate the uptake and/or breakdown of some neurotransmitters, and contribute to the formation of the blood-brain barrier?
Answer
D. astrocytes
28. Which of the following processes is not a cardinal sign of inflammation?
Answer
C. fever
29. When a mast cell reacts to an irritation, which of the following chemicals does it release?
Answer
B. histamine
30. Atrophy refers to ________.
Answer
B. loss of mass
31. Individuals can slow the rate of aging by modifying all of these lifestyle aspects except for ________.
Answer
C. genetic factors
Critical Thinking Questions
32. Identify the four types of tissue in the body, and describe the major functions of each tissue.
Answer
The four types of tissue in the body are epithelial, connective, muscle, and nervous. Epithelial tissue is made of layers of cells that cover the surfaces of the body that come into contact with the exterior world, line internal cavities, and form glands. Connective tissue binds the cells and organs of the body together and performs many functions, especially in the protection, support, and integration of the body. Muscle tissue, which responds to stimulation and contracts to provide movement, is divided into three major types: skeletal (voluntary) muscles, smooth muscles, and the cardiac muscle in the heart. Nervous tissue allows the body to receive signals and transmit information as electric impulses from one region of the body to another.
33. The zygote is described as totipotent because it ultimately gives rise to all the cells in your body including the highly specialized cells of your nervous system. Describe this transition, discussing the steps and processes that lead to these specialized cells.
Answer
The zygote divides into many cells. As these cells become specialized, they lose their ability to differentiate into all tissues. At first they form the three primary germ layers. Following the cells
OpenStax Anatomy & Physiology Instructor Answer Guide
of the ectodermal germ layer, they too become more restricted in what they can form. Ultimately,
some of these ectodermal cells become further restricted and differentiate in to nerve cells.
34. What is the function of synovial membranes?
Answer
Synovial membranes are a type of connective tissue membrane that supports mobility in joints. The membrane lines the joint cavity and contains fibroblasts that produce hyaluronan, which leads to the production of synovial fluid, a natural lubricant that enables the bones of a joint to move freely against one another.
35. The structure of a tissue usually is optimized for its function. Describe how the structure of the mucosa and its cells match its function of nutrient absorption. Answer
The mucosa of the intestine is highly folded, increasing the surface area for nutrient absorption. A greater surface area for absorption allows more nutrients to be absorbed per unit time. In addition, the nutrient-absorbing cells of the mucosa have finger-like projections called microvilli that further increase the surface area for nutrient absorption.
36. One of the main functions of connective tissue is to integrate organs and organ systems in the
body. Discuss how blood fulfills this role.
Answer
Blood is a fluid connective tissue, a variety of specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins in a liquid extracellular matrix. Blood contains formed elements derived from bone marrow. Erythrocytes, or red blood cells, transport the gases oxygen and carbon dioxide. Leukocytes, or white blood cells, are responsible for the defense of the organism against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some cells have the ability to cross the endothelial layer that lines vessels and enter adjacent tissues. Nutrients, salts, and waste are dissolved in the liquid matrix and transported through the body.
37. Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture?
Answer
A layer of dense irregular connective tissue covers cartilage. No blood vessels supply cartilage tissue. Injuries to cartilage heal very slowly because cells and nutrients needed for repair diffuse slowly to the injury site.
38. You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at.
Answer
The cells in the dish are cardiomyocytes, cardiac muscle cells. They have an intrinsic ability to contract. When they link up, they form intercalating discs that allow the cells to communicate with each other and begin contracting in synchrony.
39. Why does skeletal muscle look striated?
Answer
Under the light microscope, cells appear striated due to the arrangement of the contractile proteins actin and myosin.
40. Which morphological adaptations of neurons make them suitable for the transmission of nerve impulse?
Answer
OpenStax Anatomy & Physiology Instructor Answer Guide
Neurons are well suited for the transmission of nerve impulses because short extensions, dendrites, receive impulses from other neurons, while a long tail extension, an axon, carries electrical impulses away from the cell to other neurons.
41. What are the functions of astrocytes?
Answer
Astrocytes regulate ions and uptake and/or breakdown of some neurotransmitters and contribute to the formation of the blood-brain-barrier.
42. Why is it important to watch for increased redness, swelling and pain after a cut or abrasion has been cleaned and bandaged?
Answer
These symptoms would indicate that infection is present.
43. Aspirin is a non-steroidal anti-inflammatory drug (NSAID) that inhibits the formation of blood clots and is taken regularly by individuals with a heart condition. Steroids such as cortisol are used to control some autoimmune diseases and severe arthritis by down regulating the inflammatory response. After reading the role of inflammation in the body’s response to infection, can you predict an undesirable consequence of taking anti-inflammatory drugs on a regular basis?
Answer
Since NSAIDs or other anti-inflammatory drugs inhibit the formation of blood clots, regular and prolonged use of these drugs may promote internal bleeding, such as bleeding in the stomach. Excessive levels of cortisol would suppress inflammation, which could slow the wound healing process.
44. As an individual ages, a constellation of symptoms begins the decline to the point where an individual’s functioning is compromised. Identify and discuss two factors that have a role in factors leading to the compromised situation.
Answer
The genetic makeup and the lifestyle of each individual are factors which determine the degree of decline in cells, tissues, and organs as an individual ages.
45. Discuss changes that occur in cells as a person ages.
Answer
All cells experience changes with aging. They become larger, and many cannot divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products are not as efficient in the elderly. Cells lose their ability to function, or they begin to function abnormally, leading to disease and cancer.
Anatomy & Physiology
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Unit 2: Support and Movement
Chapter 5: The Integumentary System
Interactive Link Questions
1. The skin consists of two layers and a closely associated layer. View this animation (http://openstaxcollege.org/l/layers) to learn more about layers of the skin. What are the basic functions of each of these layers?
Answer
The epidermis provides protection, the dermis provides support and flexibility, and the hypodermis (fat layer) provides insulation and padding
2. Figure 5.4 If you zoom on the cells at the outermost layer of this section of skin, what do you notice about the cells?
Answer
These cells do not have nuclei, so you can deduce that they are dead. They appear to be sloughing off.
3. Figure 5.6 If you zoom on the cells of the stratum spinosum, what is distinctive about them?
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Answer
These cells have desmosomes, which give the cells their spiny appearance.
4. This ABC video follows the story of a pair of fraternal African-American twins, one of whom is albino. Watch this video (http://openstaxcollege.org/l/albino) to learn about the challenges these children and their family face. Which ethnicities do you think are exempt from the possibility of albinism?
Answer
There are none.
Review Questions
5. The papillary layer of the dermis is most closely associated with which layer of the epidermis?
Answer
D. stratum basale
6. Langerhans cells are commonly found in the ________.
Answer
A. stratum spinosum
7. The papillary and reticular layers of the dermis are composed mainly of ________.
Answer
C. connective tissue
8. Collagen lends ________ to the skin.
Answer
B. structure
9. Which of the following is not a function of the hypodermis?
Answer
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C. source of blood vessels in the epidermis
10. In response to stimuli from the sympathetic nervous system, the arrector pili ________.
Answer
C. are responsible for goose bumps
11. The hair matrix contains ________.
Answer
D. a layer of basal cells
12. Eccrine sweat glands ________.
Answer
B. are present in the skin throughout the body and produce watery sweat
13. Sebaceous glands ________.
Answer
B. are associated with hair follicles
14. Similar to the hair, nails grow continuously throughout our lives. Which of the following is furthest from the nail growth center?
Answer
B. hyponychium
15. In humans, exposure of the skin to sunlight is required for ________.
Answer
A. vitamin D synthesis
16. One of the functions of the integumentary system is protection. Which of the following does not directly contribute to that function?
Answer
C. folic acid synthesis
17. An individual using a sharp knife notices a small amount of blood where he just cut himself. Which of the following layers of skin did he have to cut into in order to bleed?
Answer
C. papillary dermis
18. As you are walking down the beach, you see a dead, dry, shriveled-up fish. Which layer of your epidermis keeps you from drying out?
Answer
A. stratum corneum
19. If you cut yourself and bacteria enter the wound, which of the following cells would help get rid of the bacteria?
Answer
C. Langerhans cells
20. In general, skin cancers ________.
Answer
C. can be reduced by limiting exposure to the sun
21. Bedsores ________.
Answer
C. are preventable by eliminating pressure points
22. An individual has spent too much time sun bathing. Not only is his skin painful to touch, but small blisters have appeared in the affected area. This indicates that he has damaged which layers
of his skin?
Answer
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D. epidermis and dermis
23. After a skin injury, the body initiates a wound-healing response. The first step of this response is the formation of a blood clot to stop bleeding. Which of the following would be the next response?
Answer
B. increased production of connective tissue
24. Squamous cell carcinomas are the second most common of the skin cancers and are capable of metastasizing if not treated. This cancer affects which cells?
Answer
C. keratinocytes of the stratum spinosum
Critical Thinking Questions
25. What determines the color of skin, and what is the process that darkens skin when it is exposed to UV light?
Answer
The pigment melanin, produced by melanocytes, is primarily responsible for skin color. Melanin comes in different shades of brown and black. Individuals with darker skin have darker, more abundant melanin, whereas fair-skinned individuals have a lighter shade of skin and less melanin. Exposure to UV irradiation stimulates the melanocytes to produce and secrete more melanin.
26. Cells of the epidermis derive from stem cells of the stratum basale. Describe how the cells change as they become integrated into the different layers of the epidermis.
Answer
As the cells move into the stratum spinosum, they begin the synthesis of keratin and extend cell processes, desmosomes, which link the cells. As the stratum basale continues to produce new cells, the keratinocytes of the stratum spinosum are pushed into the stratum granulosum. The cells become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin and keratohyalin. The nuclei and other cell organelles disintegrate as the cells die, leaving behind the keratin, keratohyalin, and cell membranes that form the stratum lucidum and the stratum corneum. The keratinocytes in these layers are mostly dead and flattened. Cells in the stratum corneum are periodically shed.
27. Explain the differences between eccrine and apocrine sweat glands.
Answer
Eccrine sweat glands are all over the body, especially the forehead and palms of the hand. They release a watery sweat, mixed with some metabolic waste and antibodies. Apocrine glands are associated with hair follicles. They are larger than eccrine sweat glands and lie deeper in the dermis, sometimes even reaching the hypodermis. They release a thicker sweat that is often decomposed by bacteria on the skin, resulting in an unpleasant odor.
28. Describe the structure and composition of nails.
Answer
Nails are composed of densely packed dead keratinocytes. They protect the fingers and toes from
mechanical stress. The nail body is formed on the nail bed, which is at the nail root. Nail folds, folds of skin that overlap the nail on its side, secure the nail to the body. The crescent-shaped region at the base of the nail is the lunula.
29. Why do people sweat excessively when exercising outside on a hot day?
Answer
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Sweating cools the body when it becomes warm. When the body temperature rises, such as when
exercising on a hot day, the dermal blood vessels dilate, and the sweat glands begin to secrete more sweat. The evaporation of the sweat from the surface of the skin cools the body by dissipating heat.
30. Explain your skin’s response to a drop in body core temperature.
Answer
When the core body temperature drops, the body switches to heat-conservation mode. This can include an inhibition to excessive sweating and a decrease of blood flow to the papillary layers of
the skin. This reduction of blood flow helps conserve body heat.
31. Why do teenagers often experience acne?
Answer
Acne results from a blockage of sebaceous glands by sebum. The blockage causes blackheads to form, which are susceptible to infection. The infected tissue then becomes red and inflamed. Teenagers experience this at high rates because the sebaceous glands become active during puberty. Hormones that are especially active during puberty stimulate the release of sebum, leading in many cases to blockages.
32. Why do scars look different from surrounding skin?
Answer
Scars are made of collagen and do not have the cellular structure of normal skin. The tissue is fibrous and does not allow for the regeneration of accessory structures, such as hair follicles, and sweat or sebaceous glands.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 2: Support and Movement
Chapter 6: Bone Tissue and the Skeletal System
Review Questions
1. Which function of the skeletal system would be especially important if you were in a car accident?
Answer
B. protection of internal organs
2. Bone tissue can be described as ________.
Answer
D. dense, hard connective tissue
3. Without red marrow, bones would not be able to ________.
Answer
C. make blood cells
4. Yellow marrow has been identified as ________.
Answer
A. an area of fat storage
5. Which of the following can be found in areas of movement?
Answer
B. cartilage
6. The skeletal system is made of ________.
Answer
B. bones and cartilage
7. Most of the bones of the arms and hands are long bones; however, the bones in the wrist are categorized as ________.
Answer
B. short bones
8. Sesamoid bones are found embedded in ________.
Answer
D. tendons
9. Bones that surround the spinal cord are classified as ________ bones.
Answer
A. irregular
10. Which category of bone is among the most numerous in the skeleton?
Answer
A. long bone
11. Long bones enable body movement by acting as a ________.
Answer
C. lever
12. Which of the following occurs in the spongy bone of the epiphysis?
Answer
C. hematopoiesis
13. The diaphysis contains ________.
Answer
B. fat stores
14. The fibrous membrane covering the outer surface of the bone is the ________.
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Answer
A. periosteum
15. Which of the following are incapable of undergoing mitosis?
Answer
C. osteoblasts and osteocytes
16. Which cells do not originate from osteogenic cells?
Answer
D. osteoprogenitor cells
17. Which of the following are found in compact bone and cancellous bone?
Answer
D. lacunae
18. Which of the following are only found in cancellous bone?
Answer
C. trabeculae
19. The area of a bone where the nutrient foramen passes forms what kind of bone marking?
Answer
A. a hole
20. Why is cartilage slow to heal?
Answer
C. because it does not have a blood supply
21. Why are osteocytes spread out in bone tissue?
Answer
D. Formation of osteoid spreads out the osteoblasts that formed the ossification centers.
22. In endochondral ossification, what happens to the chondrocytes?
Answer
B. They die in the calcified matrix that surrounds them and form the medullary cavity.
23. Which of the following bones is (are) formed by intramembranous ossification?
Answer
D. the flat bones of the cranium
24. Bones grow in length due to activity in the ________.
Answer
A. epiphyseal plate
25. Bones grow in diameter due to bone formation ________.
Answer
B. beneath the periosteum
26. Which of the following represents the correct sequence of zones in the epiphyseal plate?
Answer
C. calcification, maturation, proliferation, reserved
27. A fracture can be both ________.
Answer
B. open and transverse
28. How can a fractured diaphysis release fat globules into the bloodstream?
Answer
B. The yellow marrow in the diaphysis is exposed and damaged.
29. In a compound fracture, ________.
Answer
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D. broken bone pierces the skin
30. The internal and external calli are replaced by ________.
Answer
B. trabecular bone
31. The first type of bone to form during fracture repair is ________ bone.
Answer
C. spongy
32. Wolff’s law, which describes the effect of mechanical forces in bone modeling/remodeling, would predict that ________
Answer
A. a right-handed pitcher will have thicker bones in his right arm compared to his left.
33. Calcium cannot be absorbed from the small intestine if ________ is lacking.
Answer
A. vitamin D
34. Which one of the following foods is best for bone health? a
Answer
C. leafy green vegetables
35. Which of the following hormones are responsible for the adolescent growth spurt?
Answer
A. estrogen and testosterone
36. With respect to their direct effects on osseous tissue, which pair of hormones has actions that oppose each other?
Answer
D. calcitonin and parathyroid hormone
37. When calcium levels are too high or too low, which body system is primarily affected?
Answer
D. nervous system
38. All of the following play a role in calcium homeostasis except
Answer
A. thyroxine
39. Which of the following is most likely to be released when blood calcium levels are elevated?
Answer
B. calcitonin
Critical Thinking Questions
40. The skeletal system is composed of bone and cartilage and has many functions. Choose three of these functions and discuss what features of the skeletal system allow it to accomplish these functions.
Answer
It supports the body. The rigid, yet flexible skeleton acts as a framework to support the other organs of the body. It facilitates movement. The movable joints allow the skeleton to change shape and positions; that is, move. It protects internal organs. Parts of the skeleton enclose or partly enclose various organs of the body including our brain, ears, heart, and lungs. Any trauma to these organs has to be mediated through the skeletal system. It produces blood cells. The central cavity of long bones is filled with marrow. The red marrow is responsible for forming red
and white blood cells. It stores and releases minerals and fat. The mineral component of bone, in
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addition to providing hardness to bone, provides a mineral reservoir that can be tapped as needed. Additionally, the yellow marrow, which is found in the central cavity of long bones along with red marrow, serves as a storage site for fat.
41. What are the structural and functional differences between a tarsal and a metatarsal?
Answer
Structurally, a tarsal is a short bone, meaning its length, width, and thickness are about equal, while a metatarsal is a long bone whose length is greater than its width. Functionally, the tarsal provides limited motion, while the metatarsal acts as a lever.
42. What are the structural and functional differences between the femur and the patella?
Answer
Structurally, the femur is a long bone, meaning its length is greater than its width, while the patella, a sesamoid bone, is small and round. Functionally, the femur acts as a lever, while the patella protects the patellar tendon from compressive forces.
43. If the articular cartilage at the end of one of your long bones were to degenerate, what symptoms do you think you would experience? Why?
Answer
If the articular cartilage at the end of one of your long bones were to deteriorate, which is actually what happens in osteoarthritis, you would experience joint pain at the end of that bone and limitation of motion at that joint because there would be no cartilage to reduce friction between adjacent bones and there would be no cartilage to act as a shock absorber.
44. In what ways is the structural makeup of compact and spongy bone well suited to their respective functions?
Answer
The densely packed concentric rings of matrix in compact bone are ideal for resisting compressive forces, which is the function of compact bone. The open spaces of the trabeculated network of spongy bone allow spongy bone to support shifts in weight distribution, which is the function of spongy bone.
45. In what ways do intramembranous and endochondral ossification differ?
Answer
In intramembranous ossification, bone develops directly from sheets of mesenchymal connective
tissue, but in endochondral ossification, bone develops by replacing hyaline cartilage. Intramembranous ossification is complete by the end of the adolescent growth spurt, while endochondral ossification lasts into young adulthood. The flat bones of the face, most of the cranial bones, and a good deal of the clavicles (collarbones) are formed via intramembranous ossification, while bones at the base of the skull and the long bones form via endochondral ossification.
46. Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center?
Answer
A single primary ossification center is present, during endochondral ossification, deep in the periosteal collar. Like the primary ossification center, secondary ossification centers are present during endochondral ossification, but they form later, and there are two of them, one in each epiphysis
47. What is the difference between closed reduction and open reduction? In what type of fracture
would closed reduction most likely occur? In what type of fracture would open reduction most likely occur?
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Answer
In closed reduction, the broken ends of a fractured bone can be reset without surgery. Open reduction requires surgery to return the broken ends of the bone to their correct anatomical position. A partial fracture would likely require closed reduction. A compound fracture would require open reduction.
48. In terms of origin and composition, what are the differences between an internal callus and an external callus?
Answer
The internal callus is produced by cells in the endosteum and is composed of a fibrocartilaginous
matrix. The external callus is produced by cells in the periosteum and consists of hyaline cartilage and bone.
49. If you were a dietician who had a young female patient with a family history of osteoporosis, what foods would you suggest she include in her diet? Why?
Answer
Since maximum bone mass is achieved by age 30, I would want this patient to have adequate calcium and vitamin D in her diet. To do this, I would recommend ingesting milk and other dairy
foods, green leafy vegetables, and intact canned sardines so she receives sufficient calcium. Intact salmon would be a good source for calcium and vitamin D. Other fatty fish would also be a good vitamin D source.
50. During the early years of space exploration our astronauts, who had been floating in space, would return to earth showing significant bone loss dependent on how long they were in space. Discuss how this might happen and what could be done to alleviate this condition.
Answer
Astronauts floating in space were not exerting significant pressure on their bones; they were “weightless.” Without the force of gravity exerting pressure on the bones, bone mass was lost. To alleviate this condition, astronauts now do resistive exercise designed to apply forces to the bones and thus help keep them healthy.
51. An individual with very low levels of vitamin D presents themselves to you complaining of seemingly fragile bones. Explain how these might be connected.
Answer
Vitamin D is required for calcium absorption by the gut. Low vitamin D could lead to insufficient levels of calcium in the blood so the calcium is being released from the bones. The reduction of calcium from the bones can make them weak and subject to fracture.
52. Describe the effects caused when the parathyroid gland fails to respond to calcium bound to its receptors.
Answer
Under “normal” conditions, receptors in the parathyroid glands bind blood calcium. When the receptors are full, the parathyroid gland stops secreting PTH. In the condition described, the parathyroid glands are not responding to the signal that there is sufficient calcium in the blood and they keep releasing PTH, which causes the bone to release more calcium into the blood. Ultimately, the bones become fragile and hypercalcemia can result.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 2: Support and Movement
Chapter 7: Axial Skeleton
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/skull1) to view a rotating and exploded skull with color-coded bones. Which bone (yellow) is centrally located and joins with most of the other bones of the skull?
Answer
The sphenoid bone joins with most other bones of the skull. It is centrally located, where it forms
portions of the rounded brain case and cranial base.
2. View this animation (http://openstaxcollege.org/l/headblow) to see how a blow to the head may produce a contrecoup (counterblow) fracture of the basilar portion of the occipital bone on the base of the skull. Why may a basilar fracture be life threatening?
Answer
A basilar fracture may damage an artery entering the skull, causing bleeding in the brain.
3. Osteoporosis is a common age-related bone disease in which bone density and strength is decreased. Watch this video (http://openstaxcollege.org/l/osteoporosis) to get a better understanding of how thoracic vertebrae may become weakened and may fractured due to this disease. How may vertebral osteoporosis contribute to kyphosis?
Answer
Osteoporosis causes thinning and weakening of the vertebral bodies. When this occurs in thoracic vertebrae, the bodies may collapse producing kyphosis, an enhanced anterior curvature of the thoracic vertebral column.
4. Watch this animation (http://openstaxcollege.org/l/diskslip) to see what it means to “slip” a disk. Watch this second animation (http://openstaxcollege.org/l/herndisc) to see one possible treatment for a herniated disc, removing and replacing the damaged disc with an artificial one that allows for movement between the adjacent certebrae. How could lifting a heavy object produce pain in a lower limb?
Answer
Lifting a heavy object can cause an intervertebral disc in the lower back to bulge and compress a spinal nerve as it exits through the intervertebral foramen, thus producing pain in those regions of the lower limb supplied by that nerve.
5. Use this tool (http://openstaxcollege.org/l/vertcolumn) to identify the bones, intervertebral discs, and ligaments of the vertebral column. The thickest portions of the anterior longitudinal ligament and the supraspinous ligament are found in which regions of the vertebral column?
Answer
The anterior longitudinal ligament is thickest in the thoracic region of the vertebral column, while the supraspinous ligament is thickest in the lumbar region.
6. View this video (http://openstaxcollege.org/l/skullbones) to review the two processes that give
rise to the bones of the skull and body. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism?
Answer
Bones on the top and sides of the skull develop when fibrous membrane areas ossify (convert) into bone. The bones of the limbs, ribs, and vertebrae develop when cartilage models of the bones ossify into bone.
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Review Questions
7. Which of the following is part of the axial skeleton?
Answer
D. vertebral column
8. Which of the following is a function of the axial skeleton?
Answer
C. supports trunk of body
9. The axial skeleton ________.
Answer
B. forms the vertical axis of the body
10. Which of the following is a bone of the brain case?
Answer
A. parietal bone
11. The lambdoid suture joins the parietal bone to the ________.
Answer
B. occipital bone
12. The middle cranial fossa ________.
Answer
D. has the foramen rotundum, foramen ovale, and foramen spinosum
13. The paranasal sinuses are ________.
Answer
A. air-filled spaces found within the frontal, maxilla, sphenoid, and ethmoid bones only
14. Parts of the sphenoid bone include the ________.
Answer
A. sella turcica
15. The bony openings of the skull include the ________.
Answer
D. hypoglossal canal, which is located in the posterior cranial fossa
16. The cervical region of the vertebral column consists of ________.
Answer
A. seven vertebrae
17. The primary curvatures of the vertebral column ________.
Answer
B. are remnants of the original fetal curvature
18. A typical vertebra has ________.
Answer
C. lamina that spans between the transverse process and spinous process
19. A typical lumbar vertebra has ________.
Answer
A. a short, rounded spinous process
20. Which is found only in the cervical region of the vertebral column?
Answer
A. nuchal ligament
21. The sternum ________.
Answer
B. has the sternal angle located between the manubrium and body
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22. The sternal angle is the ________.
Answer
D. junction between the manubrium and body
23. The tubercle of a rib ________.
Answer
A. is for articulation with the transverse process of a thoracic vertebra
24. True ribs are ________.
Answer
D. attached via their costal cartilage directly to the sternum
25. Embryonic development of the axial skeleton involves ________.
Answer
B. endochondral ossification, which forms the ribs and sternum
26. A fontanelle ________.
Answer
D. is the area of fibrous connective tissue found at birth between the brain case bones
Critical Thinking Questions
27. Define the two divisions of the skeleton.
Answer
The axial skeleton forms the vertical axis of the body and includes the bones of the head, neck, back, and chest of the body. It consists of 80 bones that include the skull, vertebral column, and thoracic cage. The appendicular skeleton consists of 126 bones and includes all bones of the upper and lower limbs.
28. Discuss the functions of the axial skeleton
Answer
The axial skeleton supports the head, neck, back, and chest of the body and allows for movements of these body regions. It also gives bony protections for the brain, spinal cord, heart, and lungs; stores fat and minerals; and houses the blood-cell producing tissue.
29. Define and list the bones that form the brain case or support the facial structures.
Answer
The brain case is that portion of the skull that surrounds and protects the brain. It is subdivided into the rounded top of the skull, called the calvaria, and the base of the skull. There are eight bones that form the brain case. These are the paired parietal and temporal bones, plus the unpaired frontal, occipital, sphenoid, and ethmoid bones. The facial bones support the facial structures, and form the upper and lower jaws, nasal cavity, nasal septum, and orbit. There are 14
facial bones. These are the paired maxillary, palatine, zygomatic, nasal, lacrimal, and inferior nasal conchae bones, and the unpaired vomer and mandible bones.
30. Identify the major sutures of the skull, their locations, and the bones united by each.
Answer
The coronal suture passes across the top of the anterior skull. It unites the frontal bone anteriorly with the right and left parietal bones. The sagittal suture runs at the midline on the top of the skull. It unites the right and left parietal bones with each other. The squamous suture is a curved suture located on the lateral side of the skull. It unites the squamous portion of the temporal bone
to the parietal bone. The lambdoid suture is located on the posterior skull and has an inverted V-
shape. It unites the occipital bone with the right and left parietal bones.
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31. Describe the anterior, middle, and posterior cranial fossae and their boundaries, and give the midline structure that divides each into right and left areas.
Answer
The anterior cranial fossa is the shallowest of the three cranial fossae. It extends from the frontal bone anteriorly to the lesser wing of the sphenoid bone posteriorly. It is divided at the midline by
the crista galli and cribriform plates of the ethmoid bone. The middle cranial fossa is located in the central skull, and is deeper than the anterior fossa. The middle fossa extends from the lesser wing of the sphenoid bone anteriorly to the petrous ridge posteriorly. It is divided at the midline by the sella turcica. The posterior cranial fossa is the deepest fossa. It extends from the petrous ridge anteriorly to the occipital bone posteriorly. The large foramen magnum is located at the midline of the posterior fossa.
32. Describe the parts of the nasal septum in both the dry and living skull.
Answer
There are two bony parts of the nasal septum in the dry skull. The perpendicular plate of the ethmoid bone forms the superior part of the septum. The vomer bone forms the inferior and posterior parts of the septum. In the living skull, the septal cartilage completes the septum by filling in the anterior area between the bony components and extending outward into the nose.
33. Describe the vertebral column and define each region.
Answer
The adult vertebral column consists of 24 vertebrae, plus the sacrum and coccyx. The vertebrae are subdivided into cervical, thoracic, and lumbar regions. There are seven cervical vertebrae (C1–C7), 12 thoracic vertebrae (T1–T12), and five lumbar vertebrae (L1–L5). The sacrum is derived from the fusion of five sacral vertebrae and the coccyx is formed by the fusion of four small coccygeal vertebrae.
34. Describe a typical vertebra.
Answer
A typical vertebra consists of an anterior body and a posterior vertebral arch. The body serves for
weight bearing. The vertebral arch surrounds and protects the spinal cord. The vertebral arch is formed by the pedicles, which are attached to the posterior side of the vertebral body, and the lamina, which come together to form the top of the arch. A pair of transverse processes extends laterally from the vertebral arch, at the junction between each pedicle and lamina. The spinous process extends posteriorly from the top of the arch. A pair of superior articular processes project
upward and a pair of inferior articular processes project downward. Together, the notches found in the margins of the pedicles of adjacent vertebrae form an intervertebral foramen.
35. Describe the sacrum.
Answer
The sacrum is a single, triangular-shaped bone formed by the fusion of five sacral vertebrae. On the posterior sacrum, the median sacral crest is derived from the fused spinous processes, and the
lateral sacral crest results from the fused transverse processes. The sacral canal contains the sacral spinal nerves, which exit via the anterior (ventral) and posterior (dorsal) sacral foramina. The sacral promontory is the anterior lip. The sacrum also forms the posterior portion of the pelvis.
36. Describe the structure and function of an intervertebral disc.
Answer
An intervertebral disc fills in the space between adjacent vertebrae, where it provides padding and weight-bearing ability, and allows for movements between the vertebrae. It consists of an
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outer anulus fibrosus and an inner nucleus pulposus. The anulus fibrosus strongly anchors the adjacent vertebrae to each other, and the high water content of the nucleus pulposus resists compression for weight bearing and can change shape to allow for vertebral column movements.
37. Define the ligaments of the vertebral column.
Answer
The anterior longitudinal ligament is attached to the vertebral bodies on the anterior side of the vertebral column. The supraspinous ligament is located on the posterior side, where it interconnects the thoracic and lumbar spinous processes. In the posterior neck, this ligament expands to become the nuchal ligament, which attaches to the cervical spinous processes and the base of the skull. The posterior longitudinal ligament and ligamentum flavum are located inside the vertebral canal. The posterior longitudinal ligament unites the posterior sides of the vertebral bodies. The ligamentum flavum unites the lamina of adjacent vertebrae.
38. Define the parts and functions of the thoracic cage.
Answer
The thoracic cage is formed by the 12 pairs of ribs with their costal cartilages and the sternum. The ribs are attached posteriorly to the 12 thoracic vertebrae and most are anchored anteriorly either directly or indirectly to the sternum. The thoracic cage functions to protect the heart and lungs.
39. Describe the parts of the sternum.
Answer
The sternum consists of the manubrium, body, and xiphoid process. The manubrium forms the expanded, superior end of the sternum. It has a jugular (suprasternal) notch, a pair of clavicular notches for articulation with the clavicles, and receives the costal cartilage of the first rib. The manubrium is joined to the body of the sternum at the sternal angle, which is also the site for attachment of the second rib costal cartilages. The body receives the costal cartilage attachments for ribs 3–7. The small xiphoid process forms the inferior tip of the sternum.
40. Discuss the parts of a typical rib.
Answer
A typical rib is a flattened, curved bone. The head of a rib is attached posteriorly to the costal facets of the thoracic vertebrae. The rib tubercle articulates with the transverse process of a thoracic vertebra. The angle is the area of greatest rib curvature and forms the largest portion of the thoracic cage. The body (shaft) of a rib extends anteriorly and terminates at the attachment to its costal cartilage. The shallow costal groove runs along the inferior margin of a rib and carries blood vessels and a nerve.
41. Define the classes of ribs.
Answer
Ribs are classified based on if and how their costal cartilages attach to the sternum. True (vertebrosternal) ribs are ribs 1–7. The costal cartilage for each of these attaches directly to the sternum. False (vertebrochondral) ribs, 8–12, are attached either indirectly or not at all to the sternum. Ribs 8–10 are attached indirectly to the sternum. For these ribs, the costal cartilage of each attaches to the cartilage of the next higher rib. The last false ribs (11–12) are also called floating (vertebral) ribs, because these ribs do not attach to the sternum at all. Instead, the ribs and their small costal cartilages terminate within the muscles of the lateral abdominal wall.
42. Discuss the processes by which the brain-case bones of the skull are formed and grow during skull enlargement.
Answer
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The brain-case bones that form the top and sides of the skull are produced by intramembranous ossification. In this, mesenchyme from the sclerotome portion of the somites accumulates at the site of the future bone and differentiates into bone-producing cells. These generate areas of bone that are initially separated by wide regions of fibrous connective tissue called fontanelles. After birth, as the bones enlarge, the fontanelles disappear. However, the bones remain separated by the sutures, where bone and skull growth can continue until the adult size is obtained.
43. Discuss the process that gives rise to the base and facial bones of the skull.
Answer
The facial bones and base of the skull arise via the process of endochondral ossification. This process begins with the localized accumulation of mesenchyme tissue at the sites of the future bones. The mesenchyme differentiates into hyaline cartilage, which forms a cartilage model of the future bone. The cartilage allows for growth and enlargement of the model. It is gradually converted into bone over time.
44. Discuss the development of the vertebrae, ribs, and sternum.
Answer
The vertebrae, ribs, and sternum all develop via the process of endochondral ossification. Mesenchyme tissue from the sclerotome portion of the somites accumulates on either side of the notochord and produces hyaline cartilage models for each vertebra. In the thorax region, a portion of this cartilage model splits off to form the ribs. Similarly, mesenchyme forms cartilage models for the right and left halves of the sternum. The ribs then become attached anteriorly to the developing sternum, and the two halves of sternum fuse together. Ossification of the cartilage
model into bone occurs within these structures over time. This process continues until each is converted into bone, except for the sternal ends of the ribs, which remain as the costal cartilages.
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Anatomy & Physiology
Unit 2: Support and Movement
Chapter 8: The Appendicular Skeleton
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/fractures) to see how fractures of the distal radius bone can affect the wrist joint. Explain the problems that may occur if a fracture of the distal radius involves the joint surface of the radiocarpal joint of the wrist.
Answer
A fracture through the joint surface of the distal radius may make the articulating surface of the radius rough or jagged. This can then cause painful movements involving this joint and the early development of arthritis. Surgery can return the joint surface to its original smoothness, thus allowing for the return of normal function.
2. Visit this site (http://openstaxcollege.org/l/handbone) to explore the bones and joints of the hand. What are the three arches of the hand, and what is the importance of these during the gripping of an object?
Answer
The hand has a proximal transverse arch, a distal transverse arch, and a longitudinal arch. These allow the hand to conform to objects being held. These arches maximize the amount of surface contact between the hand and object, which enhances stability and increases sensory input.
3. Watch this video (http://openstaxcollege.org/l/colles) to learn about a Colles fracture, a break of the distal radius, usually caused by falling onto an outstretched hand. When would surgery be required and how would the fracture be repaired in this case?
Answer
Surgery may be required if the fracture is unstable, meaning that the broken ends of the radius won’t stay in place to allow for proper healing. In this case, metal plates and screws can be used to stabilize the fractured bone.
4. Watch this video (http://openstaxcollege.org/l/3Dpelvis) for a 3-D view of the pelvis and its associated ligaments. What is the large opening in the bony pelvis, located between the ischium and pubic regions, and what two parts of the pubis contribute to the formation of this opening?
Answer
The obturator foramen is located between the ischium and the pubis. The superior and inferior pubic rami contribute to the boundaries of the obturator foramen.
5. Watch this video (http://openstaxcollege.org/l/midfemur) to view how a fracture of the mid-
femur is surgically repaired. How are the two portions of the broken femur stabilized during surgical repair of a fractured femur?
Answer
A hole is drilled into the greater trochanter, the bone marrow (medullary) space inside the femur is enlarged, and finally an intramedullary rod is inserted into the femur. This rod is then anchored
to the bone with screws.
6. Visit this site (http://openstaxcollege.org/l/kneesurgery) to perform a virtual knee replacement surgery. The prosthetic knee components must be properly aligned to function properly. How is this alignment ensured?
Answer
Metal cutting jigs are attached to the bones to ensure that the bones are cut properly prior to the attachment of prosthetic components.
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7. Use this tutorial (http://openstaxcollege.org/l/footbones) to review the bones of the foot. Which tarsal bones are in the proximal, intermediate, and distal groups?
Answer
The proximal group of tarsal bones includes the calcaneus and talus bones, the navicular bone is intermediate, and the distal group consists of the cuboid bone plus the medial, intermediate, and lateral cuneiform bones.
8. View this link (http://openstaxcollege.org/l/bunion) to learn about a bunion, a localized swelling on the medial side of the foot, next to the first metatarsophalangeal joint, at the base of the big toe. What is a bunion and what type of shoe is most likely to cause this to develop?
Answer
A bunion results from the deviation of the big toe toward the second toe, which causes the distal end of the first metatarsal bone to stick out. A bunion may also be caused by prolonged pressure on the foot from pointed shoes with a narrow toe box that compresses the big toe and pushes it toward the second toe.
9. Watch this animation (http://openstaxcollege.org/l/limbbuds) to follow the development and growth of the upper and lower limb buds. On what days of embryonic development do these events occur: (a) first appearance of the upper limb bud (limb ridge); (b) the flattening of the distal limb to form the handplate or footplate; and (c) the beginning of limb rotation?
Answer
(a) The upper limb bud initially appears on day 26 as the upper limb ridge. This becomes the upper limb bud by day 28. (b) The handplate and footplate appear at day 36. (c) Rotation of the upper and lower limbs begins during the seventh week (day 48).
Review Questions
10. Which part of the clavicle articulates with the manubrium?
Answer
B. sternal end
11. A shoulder separation results from injury to the ________.
Answer
C. acromioclavicular joint
12. Which feature lies between the spine and superior border of the scapula?
Answer
D. supraspinous fossa
13. What structure is an extension of the spine of the scapula?
Answer
A. acromion
14. Name the short, hook-like bony process of the scapula that projects anteriorly.
Answer
C. coracoid process
15. How many bones are there in the upper limbs combined?
Answer
D. 60
16. Which bony landmark is located on the lateral side of the proximal humerus?
Answer
A. greater tubercle
17. Which region of the humerus articulates with the radius as part of the elbow joint?
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Answer
C. capitulum
18. Which is the lateral-most carpal bone of the proximal row?
Answer
D. scaphoid
19. The radius bone ________.
Answer
B. has a head that articulates with the radial notch of the ulna
20. How many bones fuse in adulthood to form the hip bone?
Answer
B. 3
21. Which component forms the superior part of the hip bone?
Answer
A. ilium
22. Which of the following supports body weight when sitting?
Answer
B. ischial tuberosity
23. The ischial spine is found between which of the following structures?
Answer
C. lesser sciatic notch and greater sciatic notch
24. The pelvis ________.
Answer
A. has a subpubic angle that is larger in females
25. Which bony landmark of the femur serves as a site for muscle attachments?
Answer
B. lesser trochanter
26. What structure contributes to the knee joint?
Answer
C. medial condyle of the tibia
27. Which tarsal bone articulates with the tibia and fibula?
Answer
D. talus
28. What is the total number of bones found in the foot and toes?
Answer
C. 26
29. The tibia ________.
Answer
C. is firmly anchored to the fibula by an interosseous membrane
30. Which event takes place during the seventh week of development?
Answer
D. the rotation of the limbs
31. During endochondral ossification of a long bone, ________.
Answer
C. growth of the epiphyseal plate will produce bone lengthening
32. The clavicle ________.
Answer
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A. develops via intramembranous ossification
Critical Thinking Questions
33. Describe the shape and palpable line formed by the clavicle and scapula.
Answer
The clavicle extends laterally across the anterior shoulder and can be palpated along its entire length. At its lateral end, the clavicle articulates with the acromion of the scapula, which forms the bony tip of the shoulder. The acromion is continuous with the spine of the scapula, which can
be palpated medially and posteriorly along its length. Together, the clavicle, acromion, and spine
of the scapula form a V-shaped line that serves as an important area for muscle attachment.
34. Discuss two possible injuries of the pectoral girdle that may occur following a strong blow to
the shoulder or a hard fall onto an outstretched hand.
Answer
A blow to the shoulder or falling onto an outstretched hand passes strong forces through the scapula to the clavicle and sternum. A hard fall may thus cause a fracture of the clavicle (broken collarbone) or may injure the ligaments of the acromioclavicular joint. In a severe case, the coracoclavicular ligament may also rupture, resulting in complete dislocation of the acromioclavicular joint (a “shoulder separation”).
35. Your friend runs out of gas and you have to help push his car. Discuss the sequence of bones and joints that convey the forces passing from your hand, through your upper limb and your pectoral girdle, and to your axial skeleton.
Answer
As you push against the car, forces will pass from the metacarpal bones of your hand into the carpal bones at the base of your hand. Forces will then pass through the midcarpal and radiocarpal joints into the radius and ulna bones of the forearm. These will pass the force through
the elbow joint into the humerus of the arm, and then through the glenohumeral joint into the scapula. The force will travel through the acromioclavicular joint into the clavicle, and then through the sternoclavicular joint into the sternum, which is part of the axial skeleton.
36. Name the bones in the wrist and hand, and describe or sketch out their locations and articulations.
Answer
The base of the hand is formed by the eight carpal bones arranged in two rows (distal and proximal) of four bones each. The proximal row contains (from lateral to medial) the scaphoid, lunate, triquetrum, and pisiform bones. The distal row contains (from medial to lateral) the hamate, capitate, trapezoid, and trapezium bones. (Use the mnemonic “So Long To Pinky, Here Comes The Thumb” to remember this sequence). The rows of the proximal and distal carpal bones articulate with each other at the midcarpal joint. The palm of the hand contains the five metacarpal bones, which are numbered 1–5 starting on the thumb side. The proximal ends of the metacarpal bones articulate with the distal row of the carpal bones. The distal ends of the metacarpal bones articulate with the proximal phalanx bones of the thumb and fingers. The thumb (digit 1) has both a proximal and distal phalanx bone. The fingers (digits 2–5) all contain proximal, middle, and distal phalanges.
37. Describe the articulations and ligaments that unite the four bones of the pelvis to each other.
Answer
The pelvis is formed by the combination of the right and left hip bones, the sacrum, and the coccyx. The auricular surfaces of each hip bone articulate with the auricular surface of the
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sacrum to form the sacroiliac joint. This joint is supported on either side by the strong anterior and posterior sacroiliac ligaments. The right and left hip bones converge anteriorly, where the pubic bodies articulate with each other to form the pubic symphysis joint. The sacrum is also attached to the hip bone by the sacrospinous ligament, which spans the sacrum to the ischial spine, and the sacrotuberous ligament, which runs from the sacrum to the ischial tuberosity. The coccyx is attached to the inferior end of the sacrum.
38. Discuss the ways in which the female pelvis is adapted for childbirth.
Answer
Compared to the male, the female pelvis is wider to accommodate childbirth. Thus, the female pelvis has greater distances between the anterior superior iliac spines and between the ischial tuberosities. The greater width of the female pelvis results in a larger subpubic angle. This angle,
formed by the anterior convergence of the right and left ischiopubic rami, is larger in females (greater than 80 degrees) than in males (less than 70 degrees). The female sacral promontory does not project anteriorly as far as it does in males, which gives the pelvic brim (pelvic inlet) of the female a rounded or oval shape. The lesser pelvic cavity is wider and more shallow in females, and the pelvic outlet is larger than in males. Thus, the greater width of the female pelvis, with its larger pelvic inlet, lesser pelvis, and pelvic outlet, are important for childbirth because the baby must pass through the pelvis during delivery.
39. Define the regions of the lower limb, name the bones found in each region, and describe the bony landmarks that articulate together to form the hip, knee, and ankle joints.
Answer
The lower limb is divided into three regions. The thigh is the region located between the hip and knee joints. It contains the femur and the patella. The hip joint is formed by the articulation between the acetabulum of the hip bone and the head of the femur. The leg is the region between the knee and ankle joints, and contains the tibia (medially) and the fibula (laterally). The knee joint is formed by the articulations between the medial and lateral condyles of the femur, and the medial and lateral condyles of the tibia. Also associated with the knee is the patella, which articulates with the patellar surface of the distal femur. The foot is found distal to the ankle and contains 26 bones. The ankle joint is formed by the articulations between the talus bone of the foot and the distal end of the tibia, the medial malleolus of the tibia, and the lateral malleolus of the fibula. The posterior foot contains the seven tarsal bones, which are the talus, calcaneus, navicular, cuboid, and the medial, intermediate, and lateral cuneiform bones. The anterior foot consists of the five metatarsal bones, which are numbered 1–5 starting on the medial side of the foot. The toes contain 14 phalanx bones, with the big toe (toe number 1) having a proximal and a
distal phalanx, and the other toes having proximal, middle, and distal phalanges.
40. The talus bone of the foot receives the weight of the body from the tibia. The talus bone then distributes this weight toward the ground in two directions: one-half of the body weight is passed
in a posterior direction and one-half of the weight is passed in an anterior direction. Describe the arrangement of the tarsal and metatarsal bones that are involved in both the posterior and anterior
distribution of body weight.
Answer
The talus bone articulates superiorly with the tibia and fibula at the ankle joint, with body weight
passed from the tibia to the talus. Body weight from the talus is transmitted to the ground by both
ends of the medial and lateral longitudinal foot arches. Weight is passed posteriorly through both
arches to the calcaneus bone, which forms the heel of the foot and is in contact with the ground. On the medial side of the foot, body weight is passed anteriorly from the talus bone to the
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navicular bone, and then to the medial, intermediate, and lateral cuneiform bones. The cuneiform
bones pass the weight anteriorly to the first, second, and third metatarsal bones, whose heads (distal ends) are in contact with the ground. On the lateral side, body weight is passed anteriorly from the talus through the calcaneus, cuboid, and fourth and fifth metatarsal bones. The talus bone thus transmits body weight posteriorly to the calcaneus and anteriorly through the navicular, cuneiform, and cuboid bones, and metatarsals one through five.
41. How can a radiograph of a child’s femur be used to determine the approximate age of that child?
Answer
A radiograph (X-ray image) of a child’s femur will show the epiphyseal plates associated with each secondary ossification center. These plates of hyaline cartilage will appear dark in comparison to the white imaging of the ossified bone. Since each epiphyseal plate appears and disappears at a different age, the presence or absence of these plates can be used to give an approximate age for the child. For example, the epiphyseal plate located at the base of the lesser trochanter of the femur appears at age 9–10 years and disappears at puberty (approximately 11 years of age). Thus, a child’s radiograph that shows the presence of the lesser trochanter epiphyseal plate indicates an approximate age of 10 years.
42. How does the development of the clavicle differ from the development of other appendicular skeleton bones?
Answer
Unlike other bones of the appendicular skeleton, the clavicle develops by the process of intramembranous ossification. In this process, embryonic mesenchyme accumulates at the site of the future bone and then differentiates directly into bone-producing tissue. Because of this direct and early production of bone, the clavicle is the first bone of the skeleton to begin to ossify. However, the growth and enlargement of the clavicle continues throughout childhood and adolescence, and thus, it is not fully ossified until 25 years of age.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 2: Support and Movement
Chapter 9: Joints
Interactive Link Questions
1. Go to this website (http://openstaxcollege.org/l/childhand) to view a radiograph (X-ray image)
of a child’s hand and wrist. The growing bones of child have an epiphyseal plate that forms a synchondrosis between the shaft and end of a long bone. Being less dense than bone, the area of epiphyseal cartilage is seen on this radiograph as the dark epiphyseal gaps located near the ends of the long bones, including the radius, ulna, metacarpal, and phalanx bones. Which of the bones in this image do not show an epiphyseal plate (epiphyseal gap)?
Answer
Although they are still growing, the carpal bones of the wrist area do not show an epiphyseal plate. Instead of elongating, these bones grow in diameter by adding new bone to their surfaces.
2. Watch this video (http://openstaxcollege.org/l/synjoints) to see an animation of synovial joints in action. Synovial joints are places where bones articulate with each other inside of a joint cavity. The different types of synovial joints are the ball-and-socket joint (shoulder joint), hinge joint (knee), pivot joint (atlantoaxial joint, between C1 and C2 vertebrae of the neck), condyloid joint (radiocarpal joint of the wrist), saddle joint (first carpometacarpal joint, between the trapezium carpal bone and the first metacarpal bone, at the base of the thumb), and plane joint (facet joints of vertebral column, between superior and inferior articular processes). Which type of synovial joint allows for the widest ranges of motion?
Answer
Ball-and-socket joint.
3. Visit this website (http://openstaxcollege.org/l/gout) to read about a patient who arrives at the hospital with joint pain and weakness in his legs. What caused this patient’s weakness?
Answer
Gout is due to the accumulation of uric acid crystals in the body. Usually these accumulate within joints, causing joint pain. This patient also had crystals that accumulated in the space next to his spinal cord, thus compressing the spinal cord and causing muscle weakness.
4. Watch this animation (http://openstaxcollege.org/l/hipreplace) to observe hip replacement surgery (total hip arthroplasty), which can be used to alleviate the pain and loss of joint mobility associated with osteoarthritis of the hip joint. What is the most common cause of hip disability?
Answer
The most common cause of hip disability is osteoarthritis, a chronic disease in which the articular cartilage of the joint wears away, resulting in severe hip pain and stiffness.
5. Watch this video (http://openstaxcollege.org/l/rheuarthritis) to learn about the symptoms and treatments for rheumatoid arthritis. Which system of the body malfunctions in rheumatoid arthritis and what does this cause?
Answer
The immune system malfunctions and attacks healthy cells in the lining of your joints. This causes inflammation and pain in the joints and surrounding tissues.
6. Watch this video (http://openstaxcollege.org/l/anatomical) to learn about anatomical motions. What motions involve increasing or decreasing the angle of the foot at the ankle?
Answer
Dorsiflexion of the foot at the ankle decreases the angle of the ankle joint, while plantar flexion increases the angle of the ankle joint.
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7. Watch this video (http://openstaxcollege.org/l/TMJ) to learn about TMJ. Opening of the mouth requires the combination of two motions at the temporomandibular joint, an anterior gliding motion of the articular disc and mandible and the downward hinging of the mandible. What is the initial movement of the mandible during opening and how much mouth opening does
this produce?
Answer
The first motion is rotation (hinging) of the mandible, but this only produces about 20 mm (0.78 in) of mouth opening.
8. Watch this video (http://openstaxcollege.org/l/shoulderjoint1) for a tutorial on the anatomy of the shoulder joint. What movements are available at the shoulder joint?
Answer
The shoulder joint is a ball-and-socket joint that allows for flexion-extension, abduction-
adduction, medial rotation, lateral rotation, and circumduction of the humerus.
9. Watch this video (http://openstaxcollege.org/l/shoulderjoint2) to learn about the anatomy of the shoulder joint, including bones, joints, muscles, nerves, and blood vessels. What is the shape of the glenoid labrum in cross-section, and what is the importance of this shape?
Answer
The glenoid labrum is wedge-shaped in cross-section. This is important because it creates an elevated rim around the glenoid cavity, which creates a deeper socket for the head of the humerus to fit into.
10. Watch this animation (http://openstaxcollege.org/l/elbowjoint1) to learn more about the anatomy of the elbow joint. What structures provide the main stability for the elbow?
Answer
The structures that stabilize the elbow include the coronoid process, the radial (lateral) collateral ligament, and the anterior portion of the ulnar (medial) collateral ligament.
11. Watch this video (http://openstaxcollege.org/l/elbowjoint2) to learn more about the anatomy of the elbow joint, including bones, joints, muscles, nerves, and blood vessels. What are the functions of the articular cartilage?
Answer
The articular cartilage functions to absorb shock and to provide an extremely smooth surface that
makes movement between bones easy, without damaging the bones.
12. Watch this video (http://openstaxcollege.org/l/ hipjoint1) for a tutorial on the anatomy of the hip joint. What is a possible consequence following a fracture of the femoral neck within the capsule of the hip joint?
Answer
An intracapsular fracture of the neck of the femur can result in disruption of the arterial blood supply to the head of the femur, which may lead to avascular necrosis of the femoral head.
13. Watch this video (http://openstaxcollege.org/l/hipjoint2) to learn more about the anatomy of the hip joint, including bones, joints, muscles, nerves, and blood vessels. Where is the articular cartilage thickest within the hip joint?
Answer
The articular cartilage is thickest in the upper and back part of the acetabulum, the socket portion
of the hip joint. These regions receive most of the force from the head of the femur during walking and running.
14. Watch this video (http://openstaxcollege.org/l/flexext) to learn more about the flexion and extension of the knee, as the femur both rolls and glides on the tibia to maintain stable contact
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between the bones in all knee positions. The patella glides along a groove on the anterior side of the distal femur. The collateral ligaments on the sides of the knee become tight in the fully extended position to help stabilize the knee. The posterior cruciate ligament supports the knee when flexed and the anterior cruciate ligament becomes tight when the knee comes into full extension to resist hyperextension. What are the ligaments that support the knee joint?
Answer
There are five ligaments associated with the knee joint. The tibial collateral ligament is located on the medial side of the knee and the fibular collateral ligament is located on the lateral side. The anterior and posterior cruciate ligaments are located inside the knee joint
15. Watch this video (http://openstaxcollege.org/l/kneejoint1) to learn more about the anatomy of
the knee joint, including bones, joints, muscles, nerves, and blood vessels. Which ligament of the
knee keeps the tibia from sliding too far forward in relation to the femur and which ligament keeps the tibia from sliding too far backward?
Answer
The anterior cruciate ligament prevents the tibia from sliding too far forward in relation to the femur and the posterior cruciate ligament keeps the tibia from sliding too far backward.
16. Watch this video (http://openstaxcollege.org/l/kneeinjury) to learn more about different knee injuries and diagnostic testing of the knee. What are the most causes of anterior cruciate ligament
injury?
Answer
The anterior cruciate ligament (ACL) is most commonly injured when traumatic force is applied to the knee during a twisting motion or when side standing or landing from a jump.
17. Watch this video (http://openstaxcollege.org/l/anklejoint1) for a tutorial on the anatomy of the ankle joint. What are the three ligaments found on the lateral side of the ankle joint?
Answer
The ligaments of the lateral ankle are the anterior and posterior talofibular ligaments and the calcaneofibular ligament. These ligaments support the ankle joint and resist excess inversion of the foot.
18. Watch this video (http://openstaxcollege.org/l/anklejoint2) to learn more about the anatomy of the ankle joint, including bones, joints, muscles, nerves, and blood vessels. The ankle joint resembles what type of joint used in woodworking?
Answer
Because of the square shape of the ankle joint, it has been compared to a mortise-and-tendon type of joint.
19. Watch this video (http://openstaxcollege.org/l/anklejoint3) to learn about the ligaments of the
ankle joint, ankle sprains, and treatment. During an inversion ankle sprain injury, all three ligaments that resist excessive inversion of the foot may be injured. What is the sequence in which these three ligaments are injured?
Answer
An inversion ankle sprain may injure all three ligaments located on the lateral side of the ankle. The sequence of injury would be the anterior talofibular ligament first, followed by the calcaneofibular ligament second, and finally, the posterior talofibular ligament third.
Review Questions
20. The joint between adjacent vertebrae that includes an invertebral disc is classified as which type of joint?
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Answer
C. amphiarthrosis
21. Which of these joints is classified as a synarthrosis?
Answer
B. the manubriosternal joint
22. Which of these joints is classified as a biaxial diarthrosis?
Answer
A. the metacarpophalangeal joint
23. Synovial joints ________.
Answer
D. are joints where the bones articulate with each other within a fluid-filled joint cavity
24. Which type of fibrous joint connects the tibia and fibula?
Answer
A. syndesmosis
25. An example of a wide fibrous joint is ________.
Answer
A. the interosseous membrane of the forearm
26. A gomphosis ________.
Answer
D. anchors a tooth to the jaw
27. A syndesmosis is ________.
Answer
C. a fibrous joint that unites parallel bones
28. A cartilaginous joint ________.
Answer
B. is called a symphysis when the bones are united by fibrocartilage
29. A synchondrosis is ________.
Answer
D. found at the first sternocostal joint of the thoracic cage
30. Which of the following are joined by a symphysis?
Answer
A. adjacent vertebrae
31. The epiphyseal plate of a growing long bone in a child is classified as a ________.
Answer
A. synchondrosis
32. Which type of joint provides the greatest range of motion?
Answer
A. ball-and-socket
33. Which type of joint allows for only uniaxial movement?
Answer
B. hinge joint
34. Which of the following is a type of synovial joint?
Answer
C. a plane joint
35. A bursa ________.
Answer
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C. prevents friction between skin and bone, or a muscle tendon and bone
36. At synovial joints, ________.
Answer
D. the joint cavity is filled with a thick, lubricating fluid
37. At a synovial joint, the synovial membrane ________.
Answer
D. secretes the lubricating synovial fluid
38. Condyloid joints ________.
Answer
B. include the radiocarpal joint
39. A meniscus is ________.
Answer
A. a fibrocartilage pad that provides padding between bones
40. The joints between the articular processes of adjacent vertebrae can contribute to which movement?
Answer
A. lateral flexion
41. Which motion moves the bottom of the foot away from the midline of the body?
Answer
C. eversion
42. Movement of a body region in a circular movement at a condyloid joint is what type of motion?
Answer
D. circumduction
43. Supination is the motion that moves the ________.
Answer
A. hand from the palm backward position to the palm forward position
44. Movement at the shoulder joint that moves the upper limb laterally away from the body is called ________.
Answer
C. abduction
45. The primary support for the glenohumeral joint is provided by the ________.
Answer
C. rotator cuff muscles
46. The proximal radioulnar joint ________.
Answer
A. is supported by the annular ligament
47. Which statement is true concerning the knee joint?
Answer
D. The medial meniscus is attached to the tibial collateral ligament.
48. The ankle joint ________.
Answer
C. is a uniaxial hinge joint
49. Which region of the vertebral column has the greatest range of motion for rotation?
Answer
B. thoracic
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50. Intramembranous ossification ________.
Answer
B. produces the bones of the top and sides of the skull
51. Synovial joints ________.
Answer
C. develop at an interzone site
52. Endochondral ossification is ________.
Answer
A. the process that replaces hyaline cartilage with bone tissue
Critical Thinking Questions
53. Define how joints are classified based on function. Describe and give an example for each functional type of joint.
Answer
Functional classification of joints is based on the degree of mobility exhibited by the joint. A synarthrosis is an immobile or nearly immobile joint. An example is the manubriosternal joint or the joints between the skull bones surrounding the brain. An amphiarthrosis is a slightly moveable joint, such as the pubic symphysis or an intervertebral cartilaginous joint. A diarthrosis
is a freely moveable joint. These are subdivided into three categories. A uniaxial diarthrosis allows movement within a single anatomical plane or axis of motion. The elbow joint is an example. A biaxial diarthrosis, such as the metacarpophalangeal joint, allows for movement along two planes or axes. The hip and shoulder joints are examples of a multiaxial diarthrosis. These allow movements along three planes or axes.
54. Explain the reasons for why joints differ in their degree of mobility.
Answer
The functional needs of joints vary and thus joints differ in their degree of mobility. A synarthrosis, which is an immobile joint, serves to strongly connect bones thus protecting internal organs such as the heart or brain. A slightly moveable amphiarthrosis provides for small movements, which in the vertebral column can add together to yield a much larger overall movement. The freedom of movement provided by a diarthrosis can allow for large movements, such as is seen with most joints of the limbs.
55. Distinguish between a narrow and wide fibrous joint and give an example of each.
Answer
Narrow fibrous joints are found at a suture, gomphosis, or syndesmosis. A suture is the fibrous joint that joins the bones of the skull to each other (except the mandible). A gomphosis is the fibrous joint that anchors each tooth to its bony socket within the upper or lower jaw. The tooth is connected to the bony jaw by periodontal ligaments. A narrow syndesmosis is found at the distal tibiofibular joint where the bones are united by fibrous connective tissue and ligaments. A syndesmosis can also form a wide fibrous joint where the shafts of two parallel bones are connected by a broad interosseous membrane. The radius and ulna bones of the forearm and the tibia and fibula bones of the leg are united by interosseous membranes.
56. The periodontal ligaments are made of collagen fibers and are responsible for connecting the roots of the teeth to the jaws. Describe how scurvy, a disease that inhibits collagen production, can affect the teeth.
Answer
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The teeth are anchored into their sockets within the bony jaws by the periodontal ligaments. This
is a gomphosis type of fibrous joint. In scurvy, collagen production is inhibited and the periodontal ligaments become weak. This will cause the teeth to become loose or even to fall out.
57. Describe the two types of cartilaginous joints and give examples of each.
Answer
Cartilaginous joints are where the adjacent bones are joined by cartilage. At a synchondrosis, the bones are united by hyaline cartilage. The epiphyseal plate of growing long bones and the first sternocostal joint that unites the first rib to the sternum are examples of synchondroses. At a symphysis, the bones are joined by fibrocartilage, which is strong and flexible. Symphysis joints include the intervertebral symphysis between adjacent vertebrae and the pubic symphysis that joins the pubic portions of the right and left hip bones.
58. Both functional and structural classifications can be used to describe an individual joint. Define the first sternocostal joint and the pubic symphysis using both functional and structural characteristics.
Answer
The first sternocostal joint is a synchondrosis type of cartilaginous joint in which hyaline cartilage unites the first rib to the manubrium of the sternum. This forms an immobile (synarthrosis) type of joint. The pubic symphysis is a slightly mobile (amphiarthrosis) cartilaginous joint, where the pubic portions of the right and left hip bones are united by fibrocartilage, thus forming a symphysis.
59. Describe the characteristic structures found at all synovial joints.
Answer
All synovial joints have a joint cavity filled with synovial fluid that is the site at which the bones of the joint articulate with each other. The articulating surfaces of the bones are covered by articular cartilage, a thin layer of hyaline cartilage. The walls of the joint cavity are formed by the connective tissue of the articular capsule. The synovial membrane lines the interior surface of
the joint cavity and secretes the synovial fluid. Synovial joints are directly supported by ligaments, which span between the bones of the joint. These may be located outside of the articular capsule (extrinsic ligaments), incorporated or fused to the wall of the articular capsule (intrinsic ligaments), or found inside of the articular capsule (intracapsular ligaments). Ligaments
hold the bones together and also serve to resist or prevent excessive or abnormal movements of the joint.
60. Describe the structures that provide direct and indirect support for a synovial joint.
Answer
Direct support for a synovial joint is provided by ligaments that strongly unite the bones of the joint and serve to resist excessive or abnormal movements. Some joints, such as the sternoclavicular joint, have an articular disc that is attached to both bones, where it provides direct support by holding the bones together. Indirect joint support is provided by the muscles and their tendons that act across a joint. Muscles will increase their contractile force to help support the joint by resisting forces acting on it.
61. Briefly define the types of joint movements available at a ball-and-socket joint.
Answer
Ball-and-socket joints are multiaxial joints that allow for flexion and extension, abduction and adduction, circumduction, and medial and lateral rotation.
62. Discuss the joints involved and movements required for you to cross your arms together in front of your chest.
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Answer
To cross your arms, you need to use both your shoulder and elbow joints. At the shoulder, the arm would need to flex and medially rotate. At the elbow, the forearm would need to be flexed.
63. Discuss the structures that contribute to support of the shoulder joint.
Answer
The shoulder joint allows for a large range of motion. The primary support for the shoulder joint is provided by the four rotator cuff muscles. These muscles serve as “dynamic ligaments” and thus can modulate their strengths of contraction as needed to hold the head of the humerus in position at the glenoid fossa. Additional but weaker support comes from the coracohumeral ligament, an intrinsic ligament that supports the superior aspect of the shoulder joint, and the glenohumeral ligaments, which are intrinsic ligaments that support the anterior side of the joint.
64. Describe the sequence of injuries that may occur if the extended, weight-bearing knee receives a very strong blow to the lateral side of the knee.
Answer
A strong blow to the lateral side of the extended knee will cause the medial side of the knee joint to open, resulting in a sequence of three injuries. First will be damage to the tibial collateral ligament. Since the medial meniscus is attached to the tibial collateral ligament, the meniscus is also injured. The third structure injured would be the anterior cruciate ligament.
65. Describe how synovial joints develop within the embryonic limb.
Answer
Mesenchyme gives rise to cartilage models of the future limb bones. An area called the joint interzone located between adjacent cartilage models will become a synovial joint. The cells at the center of the interzone die, thus producing the joint cavity. Additional mesenchyme cells at the periphery of the interzone become the articular capsule.
66. Differentiate between endochondral and intramembranous ossification.
Answer
Intramembranous ossification is the process by which mesenchymal cells differentiate directly into bone producing cells. This process produces the bones that form the top and sides of the skull. The remaining skull bones and the bones of the limbs are formed by endochondral ossification. In this, mesenchymal cells differentiate into hyaline cartilage cells that produce a cartilage model of the future bone. The cartilage is then gradually replaced by bone tissue over a period of many years, during which the cartilage of the epiphyseal plate can continue to grow to allow for enlargement or lengthening of the bone.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 2: Support and Movement
Chapter 10: Muscle Tissue
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/micromacro) to learn more about macro- and microstructures of skeletal muscles. (a) What are the names of the “junction points” between sarcomeres? (b) What are the names of the “subunits” within the myofibrils that run the length of
skeletal muscle fibers? (c) What is the “double strand of pearls” described in the video? (d) What
gives a skeletal muscle fiber its striated appearance?
Answer
(a) Z-lines. (b) Sarcomeres. (c) This is the arrangement of the actin and myosin filaments in a sarcomere. (d) The alternating strands of actin and myosin filaments.
2. Every skeletal muscle fiber is supplied by a motor neuron at the NMJ. Watch this video (http://openstaxcollege.org/l/skelmuscfiber) to learn more about what happens at the neuromuscular junction. (a) What is the definition of a motor unit? (b) What is the structural and functional difference between a large motor unit and a small motor unit? Can you give an example of each? (c) Why is the neurotransmitter acetylcholine degraded after binding to its receptor?
Answer
(a) It is the number of skeletal muscle fibers supplied by a single motor neuron. (b) A large motor unit has one neuron supplying many skeletal muscle fibers for gross movements, like the Temporalis muscle, where 1000 fibers are supplied by one neuron. A small motor has one neuron supplying few skeletal muscle fibers for very fine movements, like the extraocular eye muscles, where six fibers are supplied by one neuron. (c) To avoid prolongation of muscle contraction.
3. The release of calcium ions initiates muscle contractions. Watch this video (http://openstaxcollege.org/l/calciumrole) to learn more about the role of calcium. (a) What are “T-tubules” and what is their role? (b) Please also describe how actin-binding sites are made available for cross-bridging with myosin heads during contraction.
Answer
(a) The T-tubules are inward extensions of the sarcolemma that trigger the release of Ca
++
from SR during an Action Potential. (b) Ca
++
binds to troponin, and this slides the tropomyosin rods away from the binding sites.
Review Questions
4. Muscle that has a striped appearance is described as being ________.
Answer
D. striated
5. Which element is important in directly triggering contraction?
Answer
B. calcium (Ca
++
)
6. Which of the following properties is not common to all three muscle tissues?
Answer
C. at rest, uses shielding proteins to cover actin-binding sites
7. The correct order for the smallest to the largest unit of organization in muscle tissue is ________.
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Answer
B. filament, myofibril, muscle fiber, fascicle
8. Depolarization of the sarcolemma means ________.
Answer
A. the inside of the membrane has become less negative as sodium ions accumulate
9. In relaxed muscle, the myosin-binding site on actin is blocked by ________.
Answer
D. tropomyosin
10. According to the sliding filament model, binding sites on actin open when ________.
Answer
D. calcium ion levels rise
11. The cell membrane of a muscle fiber is called ________.
Answer
B. sarcolemma
12. Muscle relaxation occurs when ________.
Answer
C. calcium ions are actively transported into the sarcoplasmic reticulum
13. During muscle contraction, the cross-bridge detaches when ________.
Answer
B. the myosin head binds to an ATP molecule
14. Thin and thick filaments are organized into functional units called ________.
Answer
D. sarcomeres
15. During which phase of a twitch in a muscle fiber is tension the greatest?
Answer
C. contraction phase
16. Muscle fatigue is caused by ________.
Answer
B. exhaustion of energy reserves and buildup of lactic acid levels
17. A sprinter would experience muscle fatigue sooner than a marathon runner due to ________.
Answer
A. anaerobic metabolism in the muscles of the sprinter
18. What aspect of creatine phosphate allows it to supply energy to muscles?
Answer
B. phosphate bonds
19. Drug X blocks ATP regeneration from ADP and phosphate. How will muscle cells respond to this drug?
Answer
D. none of the above
20. The muscles of a professional sprinter are most likely to have ________.
Answer
A. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers
21. The muscles of a professional marathon runner are most likely to have ________.
Answer
B. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers
22. Which of the following statements is true?
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Answer
C. Fast fibers have large glycogen reserves.
23. Which of the following statements is false?
Answer
A. Slow fibers have a small network of capillaries.
24. Cardiac muscles differ from skeletal muscles in that they ________.
Answer
D. contain intercalated discs
25. If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would ________.
Answer
C. stop contracting
26. Smooth muscles differ from skeletal and cardiac muscles in that they ________.
Answer
A. lack myofibrils
27. Which of the following statements describes smooth muscle cells?
Answer
A. They are resistant to fatigue.
28. From which embryonic cell type does muscle tissue develop?
Answer
C. myoblast cells
29. Which cell type helps to repair injured muscle fibers?
Answer
D. satellite cells
Critical Thinking Questions
30. Why is elasticity an important quality of muscle tissue?
Answer
It allows muscle to return to its original length during relaxation after contraction.
31. What would happen to skeletal muscle if the epimysium were destroyed?
Answer
Muscles would lose their integrity during powerful movements, resulting in muscle damage.
32. Describe how tendons facilitate body movement.
Answer
When a muscle contracts, the force of movement is transmitted through the tendon, which pulls on the bone to produce skeletal movement.
33. What are the five primary functions of skeletal muscle?
Answer
Produce movement of the skeleton, maintain posture and body position, support soft tissues, encircle openings of the digestive, urinary, and other tracts, and maintain body temperature.
34. What are the opposite roles of voltage-gated sodium channels and voltage-gated potassium channels?
Answer
The opening of voltage-gated sodium channels, followed by the influx of Na
+
, transmits an Action Potential after the membrane has sufficiently depolarized. The delayed opening of potassium channels allows K
+
to exit the cell, to repolarize the membrane.
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35. How would muscle contractions be affected if skeletal muscle fibers did not have T-tubules?
Answer
Without T-tubules, action potential conduction into the interior of the cell would happen much more slowly, causing delays between neural stimulation and muscle contraction, resulting in slower, weaker contractions.
36. What causes the striated appearance of skeletal muscle tissue?
Answer
Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell cause the entire cell to appear striated.
37. How would muscle contractions be affected if ATP was completely depleted in a muscle fiber?
Answer
Without ATP, the myosin heads cannot detach from the actin-binding sites. All of the “stuck” cross-bridges result in muscle stiffness. In a live person, this can cause a condition like “writer’s cramps.” In a recently dead person, it results in rigor mortis.
38. Why does a motor unit of the eye have few muscle fibers compared to a motor unit of the leg?
Answer
Eyes require fine movements and a high degree of control, which is permitted by having fewer muscle fibers associated with a neuron.
39. What factors contribute to the amount of tension produced in an individual muscle fiber?
Answer
The length, size and types of muscle fiber and the frequency of neural stimulation contribute to the amount of tension produced in an individual muscle fiber.
40. Why do muscle cells use creatine phosphate instead of glycolysis to supply ATP for the first few seconds of muscle contraction?
Answer
Creatine phosphate is used because creatine phosphate and ADP are converted very quickly into ATP by creatine kinase. Glycolysis cannot generate ATP as quickly as creatine phosphate.
41. Is aerobic respiration more or less efficient than glycolysis? Explain your answer.
Answer
Aerobic respiration is much more efficient than anaerobic glycolysis, yielding 36 ATP per molecule of glucose, as opposed to two ATP produced by glycolysis.
42. What changes occur at the cellular level in response to endurance training?
Answer
Endurance training modifies slow fibers to make them more efficient by producing more mitochondria to enable more aerobic metabolism and more ATP production. Endurance exercise can also increase the amount of myoglobin in a cell and formation of more extensive capillary networks around the fiber.
43. What changes occur at the cellular level in response to resistance training?
Answer
Resistance exercises affect muscles by causing the formation of more actin and myosin, increasing the structure of muscle fibers.
44. What would be the drawback of cardiac contractions being the same duration as skeletal muscle contractions?
Answer
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An action potential could reach a cardiac muscle cell before it has entered the relaxation phase, resulting in the sustained contractions of tetanus. If this happened, the heart would not beat regularly.
45. How are cardiac muscle cells similar to and different from skeletal muscle cells?
Answer
Cardiac and skeletal muscle cells both contain ordered myofibrils and are striated. Cardiac muscle cells are branched and contain intercalated discs, which skeletal muscles do not have.
46. Why can smooth muscles contract over a wider range of resting lengths than skeletal and cardiac muscle?
Answer
Smooth muscles can contract over a wider range of resting lengths because the actin and myosin filaments in smooth muscle are not as rigidly organized as those in skeletal and cardiac muscle.
47. Describe the differences between single-unit smooth muscle and multiunit smooth muscle.
Answer
Single-unit smooth muscle is found in the walls of hollow organs; multiunit smooth muscle is found in airways to the lungs and large arteries. Single-unit smooth muscle cells contract synchronously, they are coupled by gap junctions, and they exhibit spontaneous action potential. Multiunit smooth cells lack gap junctions, and their contractions are not synchronous.
48. Why is muscle that has sustained significant damage unable to produce the same amount of power as it could before being damaged?
Answer
If the damage exceeds what can be repaired by satellite cells, the damaged tissue is replaced by scar tissue, which cannot contract.
49. Which muscle type(s) (skeletal, smooth, or cardiac) can regenerate new muscle cells/fibers? Explain your answer.
Answer
Smooth muscle tissue can regenerate from stem cells called pericytes, cells found in some small blood vessels. These allow smooth muscle cells to regenerate and repair much more readily than skeletal and cardiac muscle tissue.
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Anatomy & Physiology
Unit 2: Support and Movement
Chapter 11: The Muscular System
Review Questions
1. Which of the following is unique to the muscles of facial expression?
Answer
D. They insert into the skin.
2. Which of the following helps an agonist work?
Answer
A. a synergist
3. Which of the following statements is correct about what happens during flexion?
Answer
B. The angle between bones is decreased.
4. Which is moved the least during muscle contraction?
Answer
A. the origin
5. Which muscle has a convergent pattern of fascicles?
Answer
C. pectoralis major
6. A muscle that has a pattern of fascicles running along the long axis of the muscle has which of
the following fascicle arrangements?
Answer
C. parallel
7. Which arrangement best describes a bipennate muscle?
Answer
A. The muscle fibers feed in on an angle to a long tendon from both sides.
8. The location of a muscle’s insertion and origin can determine ________.
Answer
A. action
9. Where is the temporalis muscle located?
Answer
C. on the side of the head
10. Which muscle name does not make sense?
Answer
D. extensor minimus longus
11. Which of the following terms would be used in the name of a muscle that moves the leg away from the body?
Answer
D. abductor
12. Which of the following is a prime mover in head flexion?
Answer
C. sternocleidomastoid
13. Where is the inferior oblique muscle located?
Answer
B. in the eye socket
14. What is the action of the masseter?
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Answer
B. chewing
15. The names of the extrinsic tongue muscles commonly end in ________.
Answer
B. -glossus
16. What is the function of the erector spinae?
Answer
C. postural support
17. Which of the following abdominal muscles is not a part of the anterior abdominal wall?
Answer
A. quadratus lumborum
18. Which muscle pair plays a role in respiration?
Answer
D. diaphragm, scalene
19. What is the linea alba?
Answer
B. a long tendon that runs down the middle of the rectus abdominis
20. The rhomboid major and minor muscles are deep to the ________.
Answer
C. trapezius
21. Which muscle extends the forearm?
Answer
B. triceps brachii
22. What is the origin of the wrist flexors?
Answer
B. the medial epicondyle of the humerus
23. Which muscles stabilize the pectoral girdle?
Answer
A. axial and scapular
24. The large muscle group that attaches the leg to the pelvic girdle and produces extension of the hip joint is the ________ group.
Answer
A. gluteal
25. Which muscle produces movement that allows you to cross your legs?
Answer
D. the sartorius
26. What is the largest muscle in the lower leg?
Answer
B. gastrocnemius
27. The vastus intermedius muscle is deep to which of the following muscles?
Answer
B. rectus femoris
Critical Thinking Questions
28. What effect does fascicle arrangement have on a muscle’s action?
Answer
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Fascicle arrangements determine what type of movement a muscle can make. For instance, circular muscles act as sphincters, closing orifices.
29. Movements of the body occur at joints. Describe how muscles are arranged around the joints of the body.
Answer
Muscles work in pairs to facilitate movement of the bones around the joints. Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist
the agonists, and fixators stabilize a muscle’s origin.
30. Explain how a synergist assists an agonist by being a fixator.
Answer
Agonists are the prime movers while antagonists oppose or resist the movements of the agonists. Synergists assist the agonists, and fixators stabilize a muscle’s origin.
31. Describe the different criteria that contribute to how skeletal muscles are named.
Answer
In anatomy and physiology, many word roots are Latin or Greek. Portions, or roots, of the word give us clues about the function, shape, action, or location of a muscle.
32. Explain the difference between axial and appendicular muscles.
Answer
Axial muscles originate on the axial skeleton (the bones in the head, neck, and core of the body), whereas appendicular muscles originate on the bones that make up the body’s limbs.
33. Describe the muscles of the anterior neck.
Answer
The muscles of the anterior neck are arranged to facilitate swallowing and speech. They work on the hyoid bone, with the suprahyoid muscles pulling up and the infrahyoid muscles pulling down.
34. Why are the muscles of the face different from typical skeletal muscle?
Answer
Most skeletal muscles create movement by actions on the skeleton. Facial muscles are different in that they create facial movements and expressions by pulling on the skin—no bone movements are involved.
35. Describe the fascicle arrangement in the muscles of the abdominal wall. How do they relate to each other?
Answer
Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.
36. What are some similarities and differences between the diaphragm and the pelvic diaphragm?
Answer
Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk.
37. The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?
Answer
Tendons of the infraspinatus, supraspinatus, teres minor, and the subscapularis form the rotator cuff, which forms a foundation on which the arms and shoulders can be stabilized and move.
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38. List the general muscle groups of the shoulders and upper limbs as well as their subgroups.
Answer
The muscles that make up the shoulders and upper limbs include the muscles that position the pelvic girdle, the muscles that move the humerus, the muscles that move the forearm, and the muscles that move the wrists, hands, and fingers.
39. Which muscles form the hamstrings? How do they function together?
Answer
The biceps femoris, semimembranosus, and semitendinosus form the hamstrings. The hamstrings
flex the leg at the knee joint.
40. Which muscles form the quadriceps? How do they function together?
Answer
The rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius form the quadriceps. The quadriceps muscles extend the leg at the knee joint.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 12: The Nervous System and Nervous Tissue
Interactive Link Questions
1. In 2003, the Nobel Prize in Physiology or Medicine was awarded to Paul C. Lauterbur and Sir Peter Mansfield for discoveries related to magnetic resonance imaging (MRI). This is a tool to see the structures of the body (not just the nervous system) that depends on magnetic fields associated with certain atomic nuclei. The utility of this technique in the nervous system is that fat tissue and water appear as different shades between black and white. Because white matter is fatty (from myelin) and gray matter is not, they can be easily distinguished in MRI images. Visit the Nobel Prize website (http://openstaxcollege.org/l/nobel_2) to play an interactive game that demonstrates the use of this technology and compares it with other types of imaging technologies. Also, the results from an MRI session are compared with images obtained from x-
ray or computed tomography. How do the imaging techniques shown in this game indicate the separation of white and gray matter compared with the freshly dissected tissue shown earlier?
Answer
MRI uses the relative amount of water in tissue to distinguish different areas, so gray and white matter in the nervous system can be seen clearly in these images.
2. Visit this site (http://openstaxcollege.org/l/troublewstairs) to read about a woman that notices that her daughter is having trouble walking up the stairs. This leads to the discovery of a hereditary condition that affects the brain and spinal cord. The electromyography and MRI tests indicated deficiencies in the spinal cord and cerebellum, both of which are responsible for controlling coordinated movements. To what functional division of the nervous system would these structures belong?
Answer
They are part of the somatic nervous system, which is responsible for voluntary movements such
as walking or climbing the stairs.
3. Visit this site (http://openstaxcollege.org/l/nervetissue3) to learn about how nervous tissue is composed of neurons and glial cells. The neurons are dynamic cells with the ability to make a vast number of connections and to respond incredibly quickly to stimuli and to initiate movements based on those stimuli. They are the focus of intense research as failures in physiology can lead to devastating illnesses. Why are neurons only found in animals? Based on what this article says about neuron function, why wouldn’t they be helpful for plants or microorganisms?
Answer
Neurons enable thought, perception, and movement. Plants do not move, so they do not need this
type of tissue. Microorganisms are too small to have a nervous system. Many are single-celled, and therefore have organelles for perception and movement.
4. View the University of Michigan WebScope at http://virtualslides.med.umich.edu/Histology/ EMsmallCharts/3%20Image%20Scope%20finals/ 054%20-%20Peripheral%20nerve_001.svs/ view.apml?listview=1& (http://openstaxcollege.org/l/nervefiber) to see an electron micrograph of a crosssection of a myelinated nerve fiber. The axon contains microtubules and neurofilaments, bounded by a plasma membrane known as the axolemma. Outside the plasma membrane of the axon is the myelin sheath, which is composed of the tightly wrapped plasma membrane of a Schwann cell. What aspects of the cells in this image react with the stain that makes them the deep, dark, black color, such as the multiple layers that are the myelin sheath?
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Answer
Lipid membranes, such as the cell membrane and organelle membranes.
5. What happens across the membrane of an electrically active cell is a dynamic process that is hard to visualize with static images or through text descriptions. View this animation (http://openstaxcollege.org/l/dynamic1) to really understand the process. What is the difference between the driving force for Na
+
and K
+
? And what is similar about the movement of these two ions?
Answer
Sodium is moving into the cell because of the immense concentration gradient, whereas potassium is moving out because of the depolarization that sodium causes. However, they both move down their respective gradients, toward equilibrium.
6. Visit this site (http://openstaxcollege.org/l/neurolab) to see a virtual neurophysiology lab, and to observe electrophysiological processes in the nervous system, where scientists directly measure the electrical signals produced by neurons. Often, the action potentials occur so rapidly that watching a screen to see them occur is not helpful. A speaker is powered by the signals recorded from a neuron and it “pops” each time the neuron fires an action potential. These action
potentials are firing so fast that it sounds like static on the radio. Electrophysiologists can recognize the patterns within that static to understand what is happening. Why is the leech model
used for measuring the electrical activity of neurons instead of using humans?
Answer
The properties of electrophysiology are common to all animals, so using the leech is an easier, more humane approach to studying the properties of these cells. There are differences between the nervous systems of invertebrates (such as a leech) and vertebrates, but not for the sake of what these experiments study.
7. Watch this video (http://openstaxcollege.org/l/summation) to learn about summation. The process of converting electrical signals to chemical signals and back requires subtle changes that can result in transient increases or decreases in membrane voltage. To cause a lasting change in the target cell, multiple signals are usually added together, or summated. Does spatial summation
have to happen all at once, or can the separate signals arrive on the postsynaptic neuron at slightly different times? Explain your answer.
Answer
A second signal from a separate presynaptic neuron can arrive slightly later, as long as it arrives before the first one dies off, or dissipates.
8. Watch this video (http://openstaxcollege.org/l/neurotrans) to learn about the release of a neurotransmitter. The action potential reaches the end of the axon, called the axon terminal, and a chemical signal is released to tell the target cell to do something, either initiate a new action potential, or to suppress that activity. In a very short space, the electrical signal of the action potential is changed into the chemical signal of a neurotransmitter, and then back to electrical changes in the target cell membrane. What is the importance of voltage-gated calcium channels in the release of neurotransmitters?
Answer
The action potential depolarizes the cell membrane of the axon terminal, which contains the voltage-gated Ca
2+
channel. That voltage change opens the channel so that Ca
2+
can enter the axon terminal. Calcium ions make it possible for synaptic vesicles to release their contents through exocytosis.
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Review Questions
9. Which of the following cavities contains a component of the central nervous system?
Answer
C. cranial
10. Which structure predominates in the white matter of the brain?
Answer
A. myelinated axons
11. Which part of a neuron transmits an electrical signal to a target cell?
Answer
D. axon
12. Which term describes a bundle of axons in the peripheral nervous system?
Answer
D. nerve
13. Which functional division of the nervous system would be responsible for the physiological changes seen during exercise (e.g., increased heart rate and sweating)?
Answer
B. autonomic
14. What type of glial cell provides myelin for the axons in a tract?
Answer
A. oligodendrocyte
15. Which part of a neuron contains the nucleus?
Answer
B. soma
16. Which of the following substances is least able to cross the blood-brain barrier?
Answer
D. white blood cells
17. What type of glial cell is the resident macrophage behind the blood-brain barrier?
Answer
A. microglia
18. What two types of macromolecules are the main components of myelin?
Answer
C. lipids and proteins
19. If a thermoreceptor is sensitive to temperature sensations, what would a chemoreceptor be sensitive to?
Answer
C. molecules
20. Which of these locations is where the greatest level of integration is taking place in the example of testing the temperature of the shower?
Answer
D. cerebral cortex
21. How long does all the signaling through the sensory pathway, within the central nervous system, and through the motor command pathway take?
Answer
C. fraction of a second
22. What is the target of an upper motor neuron?
Answer
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B. lower motor neuron
23. What ion enters a neuron causing depolarization of the cell membrane?
Answer
A. sodium
24. Voltage-gated Na
+
channels open upon reaching what state?
Answer
B. threshold
25. What does a ligand-gated channel require in order to open?
Answer
B. binding of a neurotransmitter
26. What does a mechanically gated channel respond to?
Answer
A. physical stimulus
27. Which of the following voltages would most likely be measured during the relative refractory
period?
Answer
D. -80 mv
28. Which of the following is probably going to propagate an action potential fastest?
Answer
D. a thick, myelinated axon
29. How much of a change in the membrane potential is necessary for the summation of postsynaptic potentials to result in an action potential being generated?
Answer
B. +15 mV
30. A channel opens on a postsynaptic membrane that causes a negative ion to enter the cell. What type of graded potential is this?
Answer
C. hyperpolarizing
31. What neurotransmitter is released at the neuromuscular junction?
Answer
D. acetylcholine
32. What type of receptor requires an effector protein to initiate a signal?
Answer
D. metabotropic receptor
33. Which of the following neurotransmitters is associated with inhibition exclusively?
Answer
A. GABA
Critical Thinking Questions
34. What responses are generated by the nervous system when you run on a treadmill? Include an example of each type of tissue that is under nervous system control.
Answer
Running on a treadmill involves contraction of the skeletal muscles in the legs, increase in contraction of the cardiac muscle of the heart, and the production and secretion of sweat in the skin to stay cool.
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35. When eating food, what anatomical and functional divisions of the nervous system are involved in the perceptual experience?
Answer
The sensation of taste associated with eating is sensed by nerves in the periphery that are involved in sensory and somatic functions.
36. Multiple sclerosis is a demyelinating disease affecting the central nervous system. What type of cell would be the most likely target of this disease? Why?
Answer
The disease would target oligodendrocytes. In the CNS, oligodendrocytes provide the myelin for axons.
37. Which type of neuron, based on its shape, is best suited for relaying information directly from one neuron to another? Explain why.
Answer
Bipolar cells, because they have one dendrite that receives input and one axon that provides output, would be a direct relay between two other cells.
38. Sensory fibers, or pathways, are referred to as “afferent.” Motor fibers, or pathways, are referred to as “efferent.” What can you infer about the meaning of these two terms (afferent and efferent) in a structural or anatomical context?
Answer
Afferent means “toward,” as in sensory information traveling from the periphery into the CNS. Efferent means “away from,” as in motor commands that travel from the brain down the spinal cord and out into the periphery.
39. If a person has a motor disorder and cannot move their arm voluntarily, but their muscles have tone, which motor neuron—upper or lower—is probably affected? Explain why.
Answer
The upper motor neuron would be affected because it is carrying the command from the brain down.
40. What does it mean for an action potential to be an “all or none” event?
Answer
The cell membrane must reach threshold before voltage-gated Na
+
channels open. If threshold is not reached, those channels do not open, and the depolarizing phase of the action potential does not occur, the cell membrane will just go back to its resting state.
41. The conscious perception of pain is often delayed because of the time it takes for the sensations to reach the cerebral cortex. Why would this be the case based on propagation of the axon potential?
Answer
Axons of pain sensing sensory neurons are thin and unmyelinated so that it takes longer for that sensation to reach the brain than other sensations.
42. If a postsynaptic cell has synapses from five different cells, and three cause EPSPs and two of them cause IPSPs, give an example of a series of depolarizations and hyperpolarizations that would result in the neuron reaching threshold.
Answer
EPSP1 = +5 mV, EPSP2 = +7 mV, EPSP 3 = +10 mV, IPSP1 = -4 mV, IPSP2 = -3 mV. 5 + 7 + 10 – 4 – 3 = +15 mV.
43. Why is the receptor the important element determining the effect a neurotransmitter has on a target cell?
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Answer
Different neurotransmitters have different receptors. Thus, the type of receptor in the postsynaptic cell is what determines which ion channels open. Acetylcholine binding to the nicotinic receptor causes cations to cross the membrane. GABA binding to its receptor causes the
anion chloride to cross the membrane.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 13: Anatomy of the Nervous System
Interactive Link Questions
1. Watch this animation (http://openstaxcollege.org/l/braindevel) to examine the development of the brain, starting with the neural tube. As the anterior end of the neural tube develops, it enlarges into the primary vesicles that establish the forebrain, midbrain, and hindbrain. Those structures continue to develop throughout the rest of embryonic development and into adolescence. They are the basis of the structure of the fully developed adult brain. How would you describe the difference in the relative sizes of the three regions of the brain when comparing the early (25th embryonic day) brain and the adult brain?
Answer
The three regions (forebrain, midbrain, and hindbrain) appear to be approximately equal in size when they are first established, but the midbrain in the adult is much smaller than the others—
suggesting that it does not increase in size nearly as much as the forebrain or hindbrain.
2. Watch this video (http://openstaxcollege.org/l/whitematter) to learn about the white matter in the cerebrum that develops during childhood and adolescence. This is a composite of MRI images taken of the brains of people from 5 years of age through 20 years of age, demonstrating how the cerebrum changes. As the color changes to blue, the ratio of gray matter to white matter changes. The caption for the video describes it as “less gray matter,” which is another way of saying “more white matter.” If the brain does not finish developing until approximately 20 years of age, can teenagers be held responsible for behaving badly?
Answer
This is really a matter of opinion, but there are ethical issues to consider when a teenager’s behavior results in legal trouble.
3. Watch this video (http://openstaxcollege.org/l/basalnuclei1) to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the direct pathway is the shorter pathway through the system that results in increased activity in the cerebral cortex and increased motor activity. The direct pathway is described as resulting in “disinhibition” of the thalamus. What does disinhibition mean? What are the two neurons doing individually to cause this?
Answer
Both cells are inhibitory. The first cell inhibits the second one. Therefore, the second cell can no longer inhibit its target. This is disinhibition of that target across two synapses.
4. Watch this video (http://openstaxcollege.org/l/basalnuclei2) to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the indirect pathway is the longer pathway through the system
that results in decreased activity in the cerebral cortex, and therefore less motor activity. The indirect pathway has an extra couple of connections in it, including disinhibition of the subthalamic nucleus. What is the end result on the thalamus, and therefore on movement initiated
by the cerebral cortex?
Answer
By disinhibiting the subthalamic nucleus, the indirect pathway increases excitation of the globus pallidus internal segment. That, in turn, inhibits the thalamus, which is the opposite effect of the direct pathway that disinhibits the thalamus.
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5. Watch this video (http://openstaxcollege.org/l/graymatter) to learn about the gray matter of the
spinal cord that receives input from fibers of the dorsal (posterior) root and sends information out
through the fibers of the ventral (anterior) root. As discussed in this video, these connections represent the interactions of the CNS with peripheral structures for both sensory and motor functions. The cervical and lumbar spinal cords have enlargements as a result of larger populations of neurons. What are these enlargements responsible for?
Answer
There are more motor neurons in the anterior horns that are responsible for movement in the limbs. The cervical enlargement is for the arms, and the lumbar enlargement is for the legs.
6. Compared with the nearest evolutionary relative, the chimpanzee, the human has a brain that is
huge. At a point in the past, a common ancestor gave rise to the two species of humans and chimpanzees. That evolutionary history is long and is still an area of intense study. But something happened to increase the size of the human brain relative to the chimpanzee. Read this
article (http://openstaxcollege.org/l/hugebrain) in which the author explores the current understanding of why this happened. According to one hypothesis about the expansion of brain size, what tissue might have been sacrificed so energy was available to grow our larger brain? Based on what you know about that tissue and nervous tissue, why would there be a trade-off between them in terms of energy use?
Answer
Energy is needed for the brain to develop and perform higher cognitive functions. That energy is not available for the muscle tissues to develop and function. The hypothesis suggests that humans have larger brains and less muscle mass, and chimpanzees have the smaller brains but more muscle mass.
7. Watch this animation (http://openstaxcollege.org/l/bloodflow1) to see how blood flows to the brain and passes through the circle of Willis before being distributed through the cerebrum. The circle of Willis is a specialized arrangement of arteries that ensure constant perfusion of the cerebrum even in the event of a blockage of one of the arteries in the circle. The animation shows the normal direction of flow through the circle of Willis to the middle cerebral artery. Where would the blood come from if there were a blockage just posterior to the middle cerebral artery on the left?
Answer
If blood could not get to the middle cerebral artery through the posterior circulation, the blood would flow around the circle of Willis to reach that artery from an anterior vessel. Blood flow would just reverse within the circle.
8. Watch this video (http://openstaxcollege.org/l/lumbarpuncture) that describes the procedure known as the lumbar puncture, a medical procedure used to sample the CSF. Because of the anatomy of the CNS, it is a relative safe location to insert a needle. Why is the lumbar puncture performed in the lower lumbar area of the vertebral column?
Answer
The spinal cord ends in the upper lumbar area of the vertebral column, so a needle inserted lower
than that will not damage the nervous tissue of the CNS.
9. Watch this animation (http://openstaxcollege.org/l/CSFflow) that shows the flow of CSF through the brain and spinal cord, and how it originates from the ventricles and then spreads into the space within the meninges, where the fluids then move into the venous sinuses to return to the cardiovascular circulation. What are the structures that produce CSF and where are they found? How are the structures indicated in this animation?
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Answer
The choroid plexuses of the ventricles make CSF. As shown, there is a little of the blue color appearing in each ventricle that is joined by the color flowing from the other ventricles.
10. Figure 13.20 If you zoom in on the DRG, you can see smaller satellite glial cells surrounding
the large cell bodies of the sensory neurons. From what structure do satellite cells derive during embryologic development?
Answer
They derive from the neural crest.
11. Figure 13.22 To what structures in a skeletal muscle are the endoneurium, perineurium, and epineurium comparable?
Answer
The endoneurium surrounding individual nerve fibers is comparable to the endomysium surrounding myofibrils, the perineurium bundling axons into fascicles is comparable to the
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perimysium bundling muscle fibers into fascicles, and the epineurium surrounding the whole nerve is comparable to the epimysium surrounding the muscle.
12. Visit this site (http://openstaxcollege.org/l/ NYTmeningitis) to read about a man who wakes with a headache and a loss of vision. His regular doctor sent him to an ophthalmologist to address the vision loss. The ophthalmologist recognizes a greater problem and immediately sends him to the emergency room. Once there, the patient undergoes a large battery of tests, but a
definite cause cannot be found. A specialist recognizes the problem as meningitis, but the question is what caused it originally. How can that be cured? The loss of vision comes from swelling around the optic nerve, which probably presented as a bulge on the inside of the eye. Why is swelling related to meningitis going to push on the optic nerve?
Answer
The optic nerve enters the CNS in its projection from the eyes in the periphery, which means that
it crosses through the meninges. Meningitis will include swelling of those protective layers of the
CNS, resulting in pressure on the optic nerve, which can compromise vision.
Review Questions
13. Aside from the nervous system, which other organ system develops out of the ectoderm?
Answer
C. integumentary
14. Which primary vesicle of the embryonic nervous system does not differentiate into more vesicles at the secondary stage?
Answer
B. mesencephalon
15. Which adult structure(s) arises from the diencephalon?
Answer
A. thalamus, hypothalamus, retina
16. Which non-nervous tissue develops from the neuroectoderm?
Answer
D. craniofacial bone
17. Which structure is associated with the embryologic development of the peripheral nervous system?
Answer
A. neural crest
18. Which lobe of the cerebral cortex is responsible for generating motor commands?
Answer
D. frontal
19. What region of the diencephalon coordinates homeostasis?
Answer
C. hypothalamus
20. What level of the brain stem is the major input to the cerebellum?
Answer
B. pons
21. What region of the spinal cord contains motor neurons that direct the movement of skeletal muscles?
Answer
A. anterior horn
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22. Brodmann’s areas map different regions of the ________ to particular functions.
Answer
B. cerebral cortex
23. What blood vessel enters the cranium to supply the brain with fresh, oxygenated blood?
Answer
C. internal carotid artery
24. Which layer of the meninges surrounds and supports the sinuses that form the route through which blood drains from the CNS?
Answer
A. dura mater
25. What type of glial cell is responsible for filtering blood to produce CSF at the choroid plexus?
Answer
A. ependymal cell
26. Which portion of the ventricular system is found within the diencephalon?
Answer
B. third ventricle
27. What condition causes a stroke?
Answer
D. disruption of blood to the brain
28. What type of ganglion contains neurons that control homeostatic mechanisms of the body?
Answer
C. autonomic ganglion
29. Which ganglion is responsible for cutaneous sensations of the face?
Answer
D. trigeminal ganglion
30. What is the name for a bundle of axons within a nerve?
Answer
A. fascicle
31. Which cranial nerve does not control functions in the head and neck?
Answer
D. vagus
32. Which of these structures is not under direct control of the peripheral nervous system?
Answer
B. gastric plexus
Critical Thinking Questions
33. Studying the embryonic development of the nervous system makes it easier to understand the
complexity of the adult nervous system. Give one example of how development in the embryonic nervous system explains a more complex structure in the adult nervous system.
Answer
The retina, a PNS structure in the adult, grows from the diencephalon in the embryonic nervous system. The mature connections from the retina through the optic nerve/tract are to the hypothalamus and thalamus of the diencephalon, and to the midbrain, which developed directly adjacent to the diencephalon as the mesencephalon in the embryo.
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34. What happens in development that suggests that there is a special relationship between the skeletal structure of the head and the nervous system?
Answer
The neural crest gives rise to PNS structures (such as ganglia) and also to cartilage and bone of the face and cranium.
35. Damage to specific regions of the cerebral cortex, such as through a stroke, can result in specific losses of function. What functions would likely be lost by a stroke in the temporal lobe?
Answer
The temporal lobe has sensory functions associated with hearing and vision, as well as being important for memory. A stroke in the temporal lobe can result in specific sensory deficits in these systems (known as agnosias) or losses in memory
36. Why do the anatomical inputs to the cerebellum suggest that it can compare motor commands and sensory feedback?
Answer
A copy of descending input from the cerebrum to the spinal cord, through the pons, and sensory feedback from the spinal cord and special senses like balance, through the medulla, both go to the cerebellum. It can therefore send output through the midbrain that will correct spinal cord control of skeletal muscle movements.
37. Why can the circle of Willis maintain perfusion of the brain even if there is a blockage in one
part of the structure?
Answer
The structure is a circular connection of blood vessels, so that blood coming up from one of the arteries can flow in either direction around the circle and avoid any blockage or narrowing of the blood vessels.
38. Meningitis is an inflammation of the meninges that can have severe effects on neurological function. Why is infection of this structure potentially so dangerous?
Answer
The nerves that connect the periphery to the CNS pass through these layers of tissue and can be damaged by that inflammation, causing a loss of important neurological functions.
39. Why are ganglia and nerves not surrounded by protective structures like the meninges of the CNS?
Answer
The peripheral nervous tissues are out in the body, sometimes part of other organ systems. There is not a privileged blood supply like there is to the brain and spinal cord, so peripheral nervous tissues do not need the same sort of protections.
40. Testing for neurological function involves a series of tests of functions associated with the cranial nerves. What functions, and therefore which nerves, are being tested by asking a patient to follow the tip of a pen with their eyes?
Answer
The contraction of extraocular muscles is being tested, which is the function of the oculomotor, trochlear, and abducens nerves.
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Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 14: The Somatic Nervous System
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/DanielleReed) to learn about Dr. Danielle Reed of the Monell Chemical Senses Center in Philadelphia, PA, who became interested in science at an early age because of her sensory experiences. She recognized that her sense of taste was unique compared with other people she knew. Now, she studies the genetic differences between people and their sensitivities to taste stimuli. In the video, there is a brief image of a person sticking out their tongue, which has been covered with a colored dye. This is how Dr. Reed is able to visualize and count papillae on the surface of the tongue. People fall into two large groups known as “tasters” and “non-tasters” on the basis of the density of papillae on their tongue, which also indicates the number of taste buds. Non-tasters can taste food, but they are not as sensitive to certain tastes, such as bitterness. Dr. Reed discovered that she is a non-taster, which explains why she perceived bitterness differently than other people she knew. Are you very sensitive to tastes? Can you see any similarities among the members of your family?
Answer
Answers will vary, but a typical answer might be: I can eat most anything (except mushrooms!), so I don’t think that I’m that sensitive to tastes. My whole family likes eating a variety of foods, so it seems that we all have the same level of sensitivity.
2. Figure 14.9 The basilar membrane is the thin membrane that extends from the central core of the cochlea to the edge. What is anchored to this membrane so that they can be activated by movement of the fluids within the cochlea?
Answer
The hair cells are located in the organ of Corti, which is located on the basilar membrane. The stereocilia of those cells would normally be attached to the tectorial membrane (though they are detached in the micrograph because of processing of the tissue).
3. Watch this video (http://openstaxcollege.org/l/ear1) to learn more about how the structures of the ear convert sound waves into a neural signal by moving the “hairs,” or stereocilia, of the cochlear duct. Specific locations along the length of the duct encode specific frequencies, or pitches. The brain interprets the meaning of the sounds we hear as music, speech, noise, etc.
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Which ear structures are responsible for the amplification and transfer of sound from the external
ear to the inner ear?
Answer
The small bones in the middle ear, the ossicles, amplify and transfer sound between the tympanic
membrane of the external ear and the oval window of the inner ear
4. Watch this animation (http://openstaxcollege.org/l/ear2) to learn more about the inner ear and to see the cochlea unroll, with the base at the back of the image and the apex at the front. Specific wavelengths of sound cause specific regions of the basilar membrane to vibrate, much like the keys of a piano produce sound at different frequencies. Based on the animation, where do frequencies—from high to low pitches—cause activity in the hair cells within the cochlear duct?
Answer
High frequencies activate hair cells toward the base of the cochlea, and low frequencies activate hair cells toward the apex of the cochlea.
5. Watch this video (http://openstaxcollege.org/l/occipital) to learn more about a transverse section through the brain that depicts the visual pathway from the eye to the occipital cortex. The
first half of the pathway is the projection from the RGCs through the optic nerve to the lateral geniculate nucleus in the thalamus on either side. This first fiber in the pathway synapses on a thalamic cell that then projects to the visual cortex in the occipital lobe where “seeing,” or visual perception, takes place. This video gives an abbreviated overview of the visual system by concentrating on the pathway from the eyes to the occipital lobe. The video makes the statement (at 0:45) that “specialized cells in the retina called ganglion cells convert the light rays into electrical signals.” What aspect of retinal processing is simplified by that statement? Explain your answer.
Answer
Photoreceptors convert light energy, or photons, into an electrochemical signal. The retina contains bipolar cells and the RGCs that finally convert it into action potentials that are sent from
the retina to the CNS. It is important to recognize when popular media and online sources oversimplify complex physiological processes so that misunderstandings are not generated. This video was created by a medical device manufacturer who might be trying to highlight other aspects of the visual system than retinal processing. The statement they make is not incorrect, it just bundles together several steps, which makes it sound like RGCs are the transducers, rather than photoreceptors.
6. Watch this video (http://openstaxcollege.org/l/l_3-D1) to learn more about how the brain perceives 3-D motion. Similar to how retinal disparity offers 3-D moviegoers a way to extract 3-
D information from the two-dimensional visual field projected onto the retina, the brain can extract information about movement in space by comparing what the two eyes see. If movement of a visual stimulus is leftward in one eye and rightward in the opposite eye, the brain interprets this as movement toward (or away) from the face along the midline. If both eyes see an object moving in the same direction, but at different rates, what would that mean for spatial movement?
Answer
Whereas the video shows opposite movement information in each eye for an object moving toward the face on the midline, movement past one side of the head will result in movement in the same direction on both retinae, but it will be slower in the eye on the side nearer to the object.
7. The inability to recognize people by their faces is a troublesome problem. It can be caused by trauma, or it may be inborn. Watch this video (http://openstaxcollege.org/ l/faces) to learn more
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about a person who lost the ability to recognize faces as the result of an injury. She cannot recognize the faces of close family members or herself. What other information can a person suffering from prosopagnosia use to figure out whom they are seeing?
Answer
Even if a person cannot recognize a person’s face, other cues such as clothing, hairstyle, or a particular feature such as a prominent nose or facial hair, can help make an identification.
8. Watch this video (http://openstaxcollege.org/l/motorpathway) to learn more about the descending motor pathway for the somatic nervous system. The autonomic connections are mentioned, which are covered in another chapter. From this brief video, only some of the descending motor pathway of the somatic nervous system is described. Which division of the pathway is described and which division is left out?
Answer
The video only describes the lateral division of the corticospinal tract. The anterior division is omitted.
9. Visit this site (http://openstaxcollege.org/l/NYTmotor) to read about an elderly woman who starts to lose the ability to control fine movements, such as speech and the movement of limbs. Many of the usual causes were ruled out. It was not a stroke, Parkinson’s disease, diabetes, or thyroid dysfunction. The next most obvious cause was medication, so her pharmacist had to be consulted. The side effect of a drug meant to help her sleep had resulted in changes in motor control. What regions of the nervous system are likely to be the focus of haloperidol side effects?
Answer
The movement disorders were similar to those seen in movement disorders of the extrapyramidal
system, which would mean the basal nuclei are the most likely source of haloperidol side effects.
In fact, haloperidol affects dopamine activity, which is a prominent part of the chemistry of the basal nuclei.
10. Watch this video (http://openstaxcollege.org/l/reflexarc) to learn more about the reflex arc of the corneal reflex. When the right cornea senses a tactile stimulus, what happens to the left eye? Explain your answer.
Answer
The left eye also blinks. The sensory input from one eye activates the motor response of both eyes so that they both blink.
11. Watch this video (http://openstaxcollege.org/l/newreflex) to learn more about newborn reflexes. Newborns have a set of reflexes that are expected to have been crucial to survival before the modern age. These reflexes disappear as the baby grows, as some of them may be unnecessary as they age. The video demonstrates a reflex called the Babinski reflex, in which the
foot flexes dorsally and the toes splay out when the sole of the foot is lightly scratched. This is normal for newborns, but it is a sign of reduced myelination of the spinal tract in adults. Why would this reflex be a problem for an adult?
Answer
While walking, the sole of the foot may be scraped or scratched by many things. If the foot still reacted as in the Babinski reflex, an adult might lose their balance while walking.
Review Questions
12. What type of receptor cell is responsible for transducing pain stimuli?
Answer
B. nociceptor
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13. Which of these cranial nerves is part of the gustatory system?
Answer
D. facial
14. Which submodality of taste is sensitive to the pH of saliva?
Answer
B. sour
15. Axons from which neuron in the retina make up the optic nerve?
Answer
D. retinal ganglion cells
16. What type of receptor cell is involved in the sensations of sound and balance?
Answer
C. mechanoreceptor
17. Which of these sensory modalities does not pass through the ventral posterior thalamus?
Answer
C. audition
18. Which nucleus in the medulla is connected to the inferior colliculus?
Answer
D. cochlear nucleus
19. Visual stimuli in the upper-left visual field will be processed in what region of the primary visual cortex?
Answer
A. inferior right
20. Which location on the body has the largest region of somatosensory cortex representing it, according to the sensory homunculus?
Answer
A. lips
21. Which of the following is a direct target of the vestibular ganglion?
Answer
B. cerebellum
22. Which region of the frontal lobe is responsible for initiating movement by directly connecting to cranial and spinal motor neurons?
Answer
D. primary motor cortex
23. Which extrapyramidal tract incorporates equilibrium sensations with motor commands to aid in posture and movement?
Answer
B. vestibulospinal tract
24. Which region of gray matter in the spinal cord contains motor neurons that innervate skeletal muscles?
Answer
A. ventral horn
25. What type of reflex can protect the foot when a painful stimulus is sensed?
Answer
C. withdrawal reflex
26. What is the name for the topographical representation of the sensory input to the somatosensory cortex?
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Answer
A. homunculus
Critical Thinking Questions
27. The sweetener known as stevia can replace glucose in food. What does the molecular similarity of stevia to glucose mean for the gustatory sense?
Answer
The stevia molecule is similar to glucose such that it will bind to the glucose receptor in sweet-
sensitive taste buds. However, it is not a substrate for the ATP-generating metabolism within cells.
28. Why does the blind spot from the optic disc in either eye not result in a blind spot in the visual field?
Answer
The visual field for each eye is projected onto the retina as light is focused by the lens. The visual information from the right visual field falls on the left side of the retina and vice versa. The optic disc in the right eye is on the medial side of the fovea, which would be the left side of the retina. However, the optic disc in the left eye would be on the right side of that fovea, so the right visual field falls on the side of the retina in the left field where there is no blind spot.
29. Following a motorcycle accident, the victim loses the ability to move the right leg but has normal control over the left one, suggesting a hemisection somewhere in the thoracic region of the spinal cord. What sensory deficits would be expected in terms of touch versus pain? Explain your answer.
Answer
The right leg would feel painful stimuli, but not touch, because the spinothalamic tract decussates at the level of entry, which would be below the injury, whereas the dorsal column system does not decussate until reaching the brain stem, which would be above the injury and thus those fibers would be damaged.
30. A pituitary tumor can cause perceptual losses in the lateral visual field. The pituitary gland is located directly inferior to the hypothalamus. Why would this happen?
Answer
As the tumor enlarges, it would press against the optic chiasm, and fibers from the medial retina would be disrupted. These fibers carry information about the lateral visual field because the visual scene is reversed as the light passes through the pupil and lens.
31. The prefrontal lobotomy is a drastic—and largely out-of-practice—procedure used to disconnect that portion of the cerebral cortex from the rest of the frontal lobe and the diencephalon as a psychiatric therapy. Why would this have been thought necessary for someone
with a potentially uncontrollable behavior?
Answer
The prefrontal cortex is involved in decision-making functions that lead to motor responses through connections to the more posterior motor regions. These early aspects of behavior are often associated with a person’s personality, so disrupting those connections will lead to severe changes in behavior.
32. If a reflex is a limited circuit within the somatic system, why do physical and neurological exams include them to test the health of an individual?
Answer
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Though reflexes are simple circuits within the nervous system, they are representative of the more involved circuits of the somatic nervous system and can be used to quickly assess the state of neurological function for a person.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 15: The Autonomic Nervous System
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/fightflight) to learn more about adrenaline and the fight-or-flight response. When someone is said to have a rush of adrenaline, the image of bungee jumpers or skydivers usually comes to mind. But adrenaline, also known as epinephrine, is an important chemical in coordinating the body’s fight-or-flight response. In this video, you look inside the physiology of the fight-or-flight response, as envisioned for a firefighter. His body’s reaction is the result of the sympathetic division of the autonomic nervous system causing
system-wide changes as it prepares for extreme responses. What two changes does adrenaline bring about to help the skeletal muscle response?
Answer
The heart rate increases to send more blood to the muscles, and the liver releases stored glucose to fuel the muscles.
2. Watch this video (http://openstaxcollege.org/l/nervsystem1) to learn more about the nervous system. As described in this video, the nervous system has a way to deal with threats and stress that is separate from the conscious control of the somatic nervous system. The system comes from a time when threats were about survival, but in the modern age, these responses become part of stress and anxiety. This video describes how the autonomic system is only part of the response to threats, or stressors. What other organ system gets involved, and what part of the brain coordinates the two systems for the entire response, including epinephrine (adrenaline) and cortisol?
Answer
The endocrine system is also responsible for responses to stress in our lives. The hypothalamus coordinates the autonomic response through projections into the spinal cord and through influence over the pituitary gland, the effective center of the endocrine system.
3. Read this article (http://openstaxcollege.org/l/strokespell) to learn about a teenager who experiences a series of spells that suggest a stroke. He undergoes endless tests and seeks input from multiple doctors. In the end, one expert, one question, and a simple blood pressure cuff answers the question. Why would the heart have to beat faster when the teenager changes his body position from lying down to sitting, and then to standing?
Answer
The effect of gravity on circulation means that it is harder to get blood up from the legs as the body takes on a vertical orientation.
4. Watch this video (http://openstaxcollege.org/l/pupillary) to learn about the pupillary reflexes. The pupillary light reflex involves sensory input through the optic nerve and motor response through the oculomotor nerve to the ciliary ganglion, which projects to the circular fibers of the iris. As shown in this short animation, pupils will constrict to limit the amount of light falling on the retina under bright lighting conditions. What constitutes the afferent and efferent branches of the competing reflex (dilation)?
Answer
The optic nerve still carries the afferent input, but the output is from the thoracic spinal cord, through the superior cervical ganglion, to the radial fibers of the iris.
5. Watch this video (http://openstaxcollege.org/l/emotions) to learn about physical responses to emotion. The autonomic system, which is important for regulating the homeostasis of the organ
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systems, is also responsible for our physiological responses to emotions such as fear. The video summarizes the extent of the body’s reactions and describes several effects of the autonomic system in response to fear. On the basis of what you have already studied about autonomic function, which effect would you expect to be associated with parasympathetic, rather than sympathetic, activity?
Answer
The release of urine in extreme fear. The sympathetic system normally constricts sphincters such
as that of the urethra.
6. Watch this video (http://openstaxcollege.org/l/3Dmovies) to learn about the side effects of 3-D
movies. As discussed in this video, movies that are shot in 3-D can cause motion sickness, which
elicits the autonomic symptoms of nausea and sweating. The disconnection between the perceived motion on the screen and the lack of any change in equilibrium stimulates these symptoms. Why do you think sitting close to the screen or right in the middle of the theater makes motion sickness during a 3-D movie worse?
Answer
When the visual field is completely taken up by the movie, the brain is confused by the lack of vestibular stimuli to match the visual stimuli. Sitting to the side, or so that the edges of the screen
can be seen, will help by providing a stable visual cue along with the magic of the cinematic experience.
Review Questions
7. Which of these physiological changes would not be considered part of the sympathetic fight-
or-flight response?
Answer
D. increased stomach motility
8. Which type of fiber could be considered the longest?
Answer
A. preganglionic parasympathetic
9. Which signaling molecule is most likely responsible for an increase in digestive activity?
Answer
C. acetylcholine
10. Which of these cranial nerves contains preganglionic parasympathetic fibers?
Answer
B. facial, CN VII
11. Which of the following is not a target of a sympathetic preganglionic fiber?
Answer
A. intermural ganglion
12. Which of the following represents a sensory input that is not part of both the somatic and autonomic systems?
Answer
C. baroreception
13. What is the term for a reflex that does not include a CNS component?
Answer
D. short reflex
14. What neurotransmitter will result in constriction of the pupil?
Answer
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B. acetylcholine
15. What gland produces a secretion that causes fight-or-flight responses in effectors?
Answer
A. adrenal medulla
16. Which of the following is an incorrect pairing?
Answer
C. acetylcholine decreases digestion
17. Which of these locations in the forebrain is the master control center for homeostasis through
the autonomic and endocrine systems?
Answer
A. hypothalamus
18. Which nerve projects to the hypothalamus to indicate the level of light stimuli in the retina?
Answer
C. optic
19. What region of the limbic lobe is responsible for generating stress responses via the hypothalamus?
Answer
B. amygdala
20. What is another name for the preganglionic sympathetic fibers that project to the heart?
Answer
D. cardiac accelerator nerve
21. What central fiber tract connects forebrain and brain stem structures with the hypothalamus?
Answer
B. medial forebrain bundle
22. A drug that affects both divisions of the autonomic system is going to bind to, or block, which type of neurotransmitter receptor?
Answer
A. nicotinic
23. A drug is called an agonist if it ________.
Answer
C. acts like the endogenous neurotransmitter by binding to its receptor
24. Which type of drug would be an antidote to atropine poisoning?
Answer
C. muscarinic agonist
25. Which kind of drug would have anti-anxiety effects?
Answer
D. α-blocker
26. Which type of drug could be used to treat asthma by opening airways wider?
Answer
B. sympathomimetic drug
Critical Thinking Questions
27. In the context of a lioness hunting on the savannah, why would the sympathetic system not activate the digestive system?
Answer
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Whereas energy is needed for running away from the threat, blood needs to be sent to the skeletal
muscles for oxygen supply. The additional fuel, in the form of carbohydrates, probably wouldn’t improve the ability to escape the threat as much as the diversion of oxygen-rich blood would hinder it.
28. A target effector, such as the heart, receives input from the sympathetic and parasympathetic systems. What is the actual difference between the sympathetic and parasympathetic divisions at the level of those connections (i.e., at the synapse)?
Answer
The postganglionic sympathetic fiber releases norepinephrine, whereas the postganglionic parasympathetic fiber releases acetylcholine. Specific locations in the heart have adrenergic receptors and muscarinic receptors. Which receptors are bound is the signal that determines how the heart responds.
29. Damage to internal organs will present as pain associated with a particular surface area of the
body. Why would something like irritation to the diaphragm, which is between the thoracic and abdominal cavities, feel like pain in the shoulder or neck?
Answer
The nerves that carry sensory information from the diaphragm enter the spinal cord in the cervical region where somatic sensory fibers from the shoulder and neck would enter. The brain superimposes this experience onto the sensory homunculus where the somatic nerves are connected.
30. Medical practice is paying more attention to the autonomic system in considering disease states. Why would autonomic tone be important in considering cardiovascular disease?
Answer
Within the cardiovascular system, different aspects demonstrate variation in autonomic tone. Heart rate is under parasympathetic tone, and blood pressure is under sympathetic tone. Pharmaceuticals that treat cardiovascular disorders may be more effective if they work with the normal state of the autonomic system. Alternatively, some disorders may be exacerbated by autonomic deficits and common therapies might not be as effective.
31. Horner’s syndrome is a condition that presents with changes in one eye, such as pupillary constriction and dropping of eyelids, as well as decreased sweating in the face. Why could a tumor in the thoracic cavity have an effect on these autonomic functions?
Answer
Pupillary dilation and sweating, two functions lost in Horner’s syndrome, are caused by the sympathetic system. A tumor in the thoracic cavity may interrupt the output of the thoracic ganglia that project to the head and face.
32. The cardiovascular center is responsible for regulating the heart and blood vessels through homeostatic mechanisms. What tone does each component of the cardiovascular system have? What connections does the cardiovascular center invoke to keep these two systems in their resting tone?
Answer
The heart—based on the resting heart rate—is under parasympathetic tone, and the blood vessels
—based on the lack of parasympathetic input—are under sympathetic tone. The vagus nerve contributes to the lowered resting heart rate, whereas the vasomotor nerves maintain the slight constriction of systemic blood vessels.
33. Why does smoking increase the risk of heart disease? Provide two reasons based on autonomic function.
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Answer
Blood vessels, and therefore blood pressure, are primarily influenced by only the sympathetic system. There is no parasympathetic influence on blood pressure, so nicotine activation of autonomic ganglia will preferentially increase blood pressure. Also, cardiac muscle tissue is only
modulated by autonomic inputs, so the conflicting information from both sympathetic and parasympathetic postganglionic fibers will cause arrhythmias. Both hypertension and arrhythmias are cardiac risk factors.
34. Why might topical, cosmetic application of atropine or scopolamine from the belladonna plant not cause fatal poisoning, as would occur with ingestion of the plant?
Answer
Drops of these substances into the eyes, as was once done cosmetically, blocks the muscarinic receptors in the smooth muscle of the iris. The concentration of this direct application is probably
below the concentration that would cause poisoning if it got into the bloodstream. The possibility
of that concentration being wrong and causing poisoning is too great, however, for atropine to be
used as a cosmetic.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 16: The Neurological Exam
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/neuroexam) that provides a demonstration of the neurological exam—a series of tests that can be performed rapidly when a patient is initially brought into an emergency department. The exam can be repeated on a regular basis to keep a record of how and if neurological function changes over time. In what order were the sections of the neurological exam tested in this video, and which section seemed to be left out?
Answer
Coordination and gait were tested first, followed by mental status, motor, sensory, and reflexes. There were no specific tests of the cranial nerves.
2. Watch this video (http://openstaxcollege.org/l/neuroexam2) for an introduction to the neurological exam. Studying the neurological exam can give insight into how structure and function in the nervous system are interdependent. This is a tool both in the clinic and in the classroom, but for different reasons. In the clinic, this is a powerful but simple tool to assess a patient’s neurological function. In the classroom, it is a different way to think about the nervous system. Though medical technology provides noninvasive imaging and real-time functional data,
the presenter says these cannot replace the history at the core of the medical examination. What does history mean in the context of medical practice?
Answer
History is the report from the patient, or others familiar with the patient, that can assist in diagnosis and formulation of treatment and care—essentially the result of an interview with the patient.
3. Read this article (http://openstaxcollege.org/l/3word) to learn about a young man who texts his
fiancée in a panic as he finds that he is having trouble remembering things. At the hospital, a neurologist administers the mental status exam, which is mostly normal except for the three-
word recall test. The young man could not recall them even 30 seconds after hearing them and repeating them back to the doctor. An undiscovered mass in the mediastinum region was found to be Hodgkin’s lymphoma, a type of cancer that affects the immune system and likely caused antibodies to attack the nervous system. The patient eventually regained his ability to remember, though the events in the hospital were always elusive. Considering that the effects on memory were temporary, but resulted in the loss of the specific events of the hospital stay, what regions of the brain were likely to have been affected by the antibodies and what type of memory does that represent?
Answer
The patient was unable to form episodic memories during the events described in the case, so the
medial temporal lobe structures might have been affected by the antibodies.
4. Watch the video (http://openstaxcollege.org/l/2brains) titled “The Man With Two Brains” to see the neuroscientist Michael Gazzaniga introduce a patient he has worked with for years who has had his corpus callosum cut, separating his two cerebral hemispheres. A few tests are run to demonstrate how this manifests in tests of cerebral function. Unlike normal people, this patient can perform two independent tasks at the same time because the lines of communication between
the right and left sides of his brain have been removed. Whereas a person with an intact corpus callosum cannot overcome the dominance of one hemisphere over the other, this patient can. If
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the left cerebral hemisphere is dominant in the majority of people, why would right-handedness be most common?
Answer
The left hemisphere of the cerebrum controls the right side of the body through the corticospinal tract. Because language function is largely associated with the dominant hemisphere, the hand with which a person writes will most likely be the one controlled by the left hemisphere.
5. Watch this short video (http://openstaxcollege.org/l/facialnerve) to see an examination of the facial nerve using some simple tests. The facial nerve controls the muscles of facial expression. Severe deficits will be obvious in watching someone use those muscles for normal control. One side of the face might not move like the other side. But directed tests, especially for contraction against resistance, require a formal testing of the muscles. The muscles of the upper and lower face need to be tested. The strength test in this video involves the patient squeezing her eyes shut
and the examiner trying to pry her eyes open. Why does the examiner ask her to try a second time?
Answer
She has just demonstrated voluntary control by closing her eyes, but when he provides the resistance that she needs to hold tight against, she has already relaxed the muscles enough for him to pull them open. She needs to squeeze them tighter to demonstrate the strength she has in the orbicular oculi.
6. Watch this video (http://openstaxcollege.org/l/2point) to see a quick demonstration of two-
point discrimination. Touching a specialized caliper to the surface of the skin will measure the distance between two points that are perceived as distinct stimuli versus a single stimulus. The patient keeps their eyes closed while the examiner switches between using both points of the caliper or just one. The patient then must indicate whether one or two stimuli are in contact with the skin. Why is the distance between the caliper points closer on the fingertips as opposed to the
palm of the hand? And what do you think the distance would be on the arm, or the shoulder?
Answer
The fingertips are the most sensitive skin on the hand, so the points of the caliper can be closer together and still be recognized as two separate points. On the palm, the sensitivity is less, so the points need to be farther apart. This will continue on the arm and shoulder, as sensitivity decreases, the discrimination of separate stimuli will be wider.
7. Watch this video (http://openstaxcollege.org/l/reflextest) to see how to test reflexes in the abdomen. Testing reflexes of the trunk is not commonly performed in the neurological exam, but
if findings suggest a problem with the thoracic segments of the spinal cord, a series of superficial
reflexes of the abdomen can localize function to those segments. If contraction is not observed when the skin lateral to the umbilicus (belly button) is stimulated, what level of the spinal cord may be damaged?
Answer
The region lateral to the umbilicus is innervated by T9–T11, approximately. A lack of contraction following that stimulation would therefore suggest damage at those levels.
8. Watch this short video (http://openstaxcollege.org/l/stationtest) to see a test for station. Station
refers to the position a person adopts when they are standing still. The examiner would look for issues with balance, which coordinates proprioceptive, vestibular, and visual information in the cerebellum. To test the ability of a subject to maintain balance, asking them to stand or hop on one foot can be more demanding. The examiner may also push the subject to see if they can
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maintain balance. An abnormal finding in the test of station is if the feet are placed far apart. Why would a wide stance suggest problems with cerebellar function?
Answer
A wide stance would suggest the person needs to maintain balance by broadening their base. Instead of continuous correction to posture, this can keep the body stable when the cerebellum cannot.
Review Questions
9. Which major section of the neurological exam is most likely to reveal damage to the cerebellum?
Answer
D. coordination exam
10. What function would most likely be affected by a restriction of a blood vessel in the cerebral cortex?
Answer
A. language
11. Which major section of the neurological exam includes subtests that are sometimes considered a separate set of tests concerned with walking?
Answer
C. coordination exam
12. Memory, emotional, language, and sensorimotor deficits together are most likely the result of
what kind of damage?
Answer
B. developmental disorder
13. Where is language function localized in the majority of people?
Answer
D. left cerebral hemisphere
14. Which of the following could be elements of cytoarchitecture, as related to Brodmann’s microscopic studies of the cerebral cortex?
Answer
C. number of neurons per square millimeter
15. Which of the following could be a multimodal integrative area?
Answer
D. Wernicke’s area
16. Which is an example of episodic memory?
Answer
B. your last birthday party
17. Which type of aphasia is more like hearing a foreign language spoken?
Answer
A. receptive aphasia
18. What region of the cerebral cortex is associated with understanding language, both from another person and the language a person generates himself or herself?
Answer
C. superior temporal gyrus
19. Without olfactory sensation to complement gustatory stimuli, food will taste bland unless it is
seasoned with which substance?
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Answer
A. salt
20. Which of the following cranial nerves is not part of the VOR?
Answer
A. optic
21. Which nerve is responsible for controlling the muscles that result in the gag reflex?
Answer
D. vagus
22. Which nerve is responsible for taste, as well as salivation, in the anterior oral cavity?
Answer
A. facial
23. Which of the following nerves controls movements of the neck?
Answer
C. spinal accessory
24. Which of the following is not part of the corticospinal pathway?
Answer
A. cerebellar deep white matter
25. Which subtest is directed at proprioceptive sensation?
Answer
D. Romberg test
26. What term describes the inability to lift the arm above the level of the shoulder?
Answer
B. paresis
27. Which type of reflex is the jaw-jerk reflex that is part of the cranial nerve exam for the vestibulocochlear nerve?
Answer
C. stretch reflex
28. Which of the following is a feature of both somatic and visceral senses?
Answer
D. involves an axon in the ventral nerve root
29. Which white matter structure carries information from the cerebral cortex to the cerebellum?
Answer
C. middle cerebellar peduncle
30. Which region of the cerebellum receives proprioceptive input from the spinal cord?
Answer
A. vermis
31. Which of the following tests cerebellar function related to gait?
Answer
B. station
32. Which of the following is not a cause of cerebellar ataxia?
Answer
C. antibiotics
33. Which of the following functions cannot be attributed to the cerebellum?
Answer
D. processing visual information
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Critical Thinking Questions
34. Why is a rapid assessment of neurological function important in an emergency situation?
Answer
If an ischemic event has occurred, nervous tissue may be compromised, but quick intervention—
possibly within a few hours—may be the critical aspect of recovery.
35. How is the diagnostic category of TIA different from a stroke?
Answer
The main difference between a stroke and TIA is time. If the result of a cerebrovascular accident lasts longer than 24 hours, then it is considered a stroke. Otherwise, it is considered transient and is labeled a TIA.
36. A patient’s performance of the majority of the mental status exam subtests is in line with the expected norms, but the patient cannot repeat a string of numbers given by the examiner. What is
a likely explanation?
Answer
The patient has suffered a stroke to the prefrontal cortex where working memory is localized.
37. A patient responds to the question “What is your name?” with a look of incomprehension. Which of the two major language areas is most likely affected and what is the name for that type of aphasia?
Answer
Wernicke’s area is associated with the comprehension of language, so the person probably doesn’t understand the question being asked and cannot respond meaningfully. This is called a receptive aphasia.
38. As a person ages, their ability to focus on near objects (accommodation) changes. If a person is already myopic (near-sighted), why would corrective lenses not be necessary to read a book or
computer screen?
Answer
If the person already has problems focusing on far objects, and wears corrective lenses to see farther objects, then as accommodation changes, focusing on a reading surface might still be in their naturally near-sighted range.
39. When a patient flexes their neck, the head tips to the right side. Also, their tongue sticks out slightly to the left when they try to stick it straight out. Where is the damage to the brain stem most likely located?
Answer
The medulla is where the accessory nerve, which controls the sternocleidomastoid muscle, and the hypoglossal nerve, which controls the genioglossus muscle, are both located. The weakness of the left side of the neck, and the tendency of the tongue to point to that side, both show that the damage is on the left side of the brain stem.
40. The location of somatosensation is based on the topographical map of sensory innervation. What does this mean?
Answer
Where spinal nerves innervate the skin is represented by “slices” of the body surface referred to as dermatomes. The fibers originating in each region are contained within the same spinal nerve, which relates to the perception of that localization.
41. Why are upper motor neuron lesions characterized by “spastic paralysis”?
Answer
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Paralysis means that voluntary muscle control is not possible because of the interruption of descending motor input. Spasticity refers to what could be called “hypercontractility” of the muscles in the absence of the descending input.
42. Learning to ride a bike is a motor function dependent on the cerebellum. Why are the different regions of the cerebellum involved in this complex motor learning?
Answer
The spinocerebellum is related to controlling the axial muscles and keeps the body balanced on the bike. The cerebrocerebellum is related to controlling the appendicular muscles and keeps the legs moving to pedal the bike. The vestibulocerebellum receives input about equilibrium to help keep everything balanced as the bike is moving forward.
43. Alcohol intoxication can produce slurred speech. How is this related to cerebellar function?
Answer
Rapid alternating movements in speech relate to how the lips, tongue, and palate move to produce speech sounds. The cerebrocerebellum is required for the proper implementation of these movements.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 3: Regulation, Integration, and Control
Chapter 17: The Endocrine System
Interactive Link Questions
1. Visit this link (http://openstaxcollege.org/l/hormonebind) to watch an animation of the events that occur when a hormone binds to a cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells by epinephrine?
Answer
cAMP
2. Visit this link (http://openstaxcollege.org/l/roleofhypo) to watch an animation showing the role of the hypothalamus and the pituitary gland. Which hormone is released by the pituitary to stimulate the thyroid gland?
Answer
Thyroid-stimulating hormone.
3. Visit this link (http://openstaxcollege.org/l/adrenalglands) to view an animation describing the location and function of the adrenal glands. Which hormone produced by the adrenal glands is responsible for mobilization of energy stores?
Answer
Cortisol.
4. Visit this link (http://openstaxcollege.org/l/melatonin) to view an animation describing the function of the hormone melatonin. What should you avoid doing in the middle of your sleep cycle that would lower melatonin?
Answer
Turning on the lights.
5. Visit this link (http://openstaxcollege.org/l/pancreas1) to view an animation describing the location and function of the pancreas. What goes wrong in the function of insulin in type 2 diabetes?
Answer
Insulin is overproduced.
Review Questions
6. Endocrine glands ________.
Answer
C. secrete chemical messengers that travel in the bloodstream
7. Chemical signaling that affects neighboring cells is called ________.
Answer
B. paracrine
8. A newly developed pesticide has been observed to bind to an intracellular hormone receptor. If ingested, residue from this pesticide could disrupt levels of ________.
Answer
B. thyroid hormone
9. A small molecule binds to a G protein, preventing its activation. What direct effect will this have on signaling that involves cAMP?
Answer
B. Adenylyl cyclase will not be activated.
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10. A student is in a car accident, and although not hurt, immediately experiences pupil dilation, increased heart rate, and rapid breathing. What type of endocrine system stimulus did the student
receive?
Answer
C. neural
11. The hypothalamus is functionally and anatomically connected to the posterior pituitary lobe by a bridge of ________.
Answer
B. nerve axons
12. Which of the following is an anterior pituitary hormone?
Answer
C. TSH
13. How many hormones are produced by the posterior pituitary?
Answer
A. 0
14. Which of the following hormones contributes to the regulation of the body’s fluid and electrolyte balance?
Answer
B. antidiuretic hormone
15. Which of the following statements about the thyroid gland is true?
Answer
D. all of the above (It is located anterior to the trachea and inferior to the larynx, The parathyroid
glands are embedded within it, It manufactures three hormones)
16. The secretion of thyroid hormones is controlled by ________.
Answer
B. TSH from the anterior pituitary
17. The development of a goiter indicates that ________.
Answer
C. there is an excessive accumulation of colloid in the thyroid follicles
18. Iodide ions cross from the bloodstream into follicle cells via ________.
Answer
C. active transport
19. When blood calcium levels are low, PTH stimulates ________.
Answer
D. the activity of osteoclasts
20. Which of the following can result from hyperparathyroidism?
Answer
B. fractures
21. The adrenal glands are attached superiorly to which organ?
Answer
C. kidneys
22. What secretory cell type is found in the adrenal medulla?
Answer
A. chromaffin cells
23. Cushing’s disease is a disorder caused by ________.
Answer
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B. abnormally high levels of cortisol
24. Which of the following responses s not part of the fight-or-flight response?
Answer
D. reduced mental activity
25. What cells secrete melatonin?
Answer
B. pinealocytes
26. The production of melatonin is inhibited by ________.
Answer
B. exposure to bright light
27. The gonads produce what class of hormones?
Answer
C. steroid hormones
28. The production of FSH by the anterior pituitary is reduced by which hormone?
Answer
D. inhibin
29. The function of the placental hormone human placental lactogen (hPL) is to ________.
Answer
A. prepare the breasts for lactation
30. If an autoimmune disorder targets the alpha cells, production of which hormone would be directly affected?
Answer
D. glucagon
31. Which of the following statements about insulin is true?
Answer
B. Insulin facilitates the movement of intracellular glucose transporters to the cell membrane.
32. The walls of the atria produce which hormone?
Answer
B. atrial natriuretic peptide
33. The end result of the RAAS is to ________.
Answer
D. increase blood pressure
34. Athletes may take synthetic EPO to boost their ________.
Answer
C. blood oxygen levels
35. Hormones produced by the thymus play a role in the ________.
Answer
A. development of T cells
36. The anterior pituitary gland develops from which embryonic germ layer?
Answer
A. oral ectoderm
37. In the elderly, decreased thyroid function causes ________.
Answer
B. decreased basal metabolic rate
Critical Thinking Questions
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38. Describe several main differences in the communication methods used by the endocrine system and the nervous system.
Answer
The endocrine system uses chemical signals called hormones to convey information from one part of the body to a distant part of the body. Hormones are released from the endocrine cell into the extracellular environment, but then travel in the bloodstream to target tissues. This communication and response can take seconds to days. In contrast, neurons transmit electrical signals along their axons. At the axon terminal, the electrical signal prompts the release of a chemical signal called a neurotransmitter that carries the message across the synaptic cleft to elicit a response in the neighboring cell. This method of communication is nearly instantaneous, of very brief duration, and is highly specific.
39. Compare and contrast endocrine and exocrine glands.
Answer
Endocrine glands are ductless. They release their secretion into the surrounding fluid, from which it enters the bloodstream or lymph to travel to distant cells. Moreover, the secretions of endocrine glands are hormones. Exocrine glands release their secretions through a duct that delivers the secretion to the target location. Moreover, the secretions of exocrine glands are not hormones, but compounds that have an immediate physiologic function. For example, pancreatic
juice contains enzymes that help digest food.
40. True or false: Neurotransmitters are a special class of paracrines. Explain your answer.
Answer
True. Neurotransmitters can be classified as paracrines because, upon their release from a neuron’s axon terminals, they travel across a microscopically small cleft to exert their effect on a
nearby neuron or muscle cell.
41. Compare and contrast the signaling events involved with the second messengers cAMP and IP
3
.
Answer
In both cAMP and IP3–calcium signaling, a hormone binds to a cell membrane hormone receptor that is coupled to a G protein. The G protein becomes activated when the hormone binds. In the case of cAMP signaling, the activated G protein activates adenylyl cyclase, which causes ATP to be converted to cAMP. This second messenger can then initiate other signaling events, such as a phosphorylation cascade. In the case of IP
3
–calcium signaling, the activated G protein activates phospholipase C, which cleaves a membrane phospholipid compound into DAG
and IP
3
. IP
3
causes the release of calcium, another second messenger, from intracellular stores. This causes further signaling events.
42. Describe the mechanism of hormone response resulting from the binding of a hormone with an intracellular receptor.
Answer
An intracellular hormone receptor is located within the cell. A hydrophobic hormone diffuses through the cell membrane and binds to the intracellular hormone receptor, which may be in the cytosol or in the cell nucleus. This hormone–receptor complex binds to a segment of DNA. This initiates the transcription of a target gene, the end result of which is protein assembly and the hormonal response.
43. Compare and contrast the anatomical relationship of the anterior and posterior lobes of the pituitary gland to the hypothalamus.
Answer
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The anterior lobe of the pituitary gland is connected to the hypothalamus by vasculature, which allows regulating hormones from the hypothalamus to travel to the anterior pituitary. In contrast, the posterior lobe is connected to the hypothalamus by a bridge of nerve axons called the hypothalamic–hypophyseal tract, along which the hypothalamus sends hormones produced by hypothalamic nerve cell bodies to the posterior pituitary for storage and release into the circulation.
44. Name the target tissues for prolactin.
Answer
The mammary glands are the target tissues for prolactin.
45. Explain why maternal iodine deficiency might lead to neurological impairment in the fetus.
Answer
Iodine deficiency in a pregnant woman would also deprive the fetus. Iodine is required for the synthesis of thyroid hormones, which contribute to fetal growth and development, including maturation of the nervous system. Insufficient amounts would impair these functions.
46. Define hyperthyroidism and explain why one of its symptoms is weight loss.
Answer
Hyperthyroidism is an abnormally elevated blood level of thyroid hormones due to an overproduction of T
3
and T
4
. An individual with hyperthyroidism is likely to lose weight because
one of the primary roles of thyroid hormones is to increase the body’s basal metabolic rate, increasing the breakdown of nutrients and the production of ATP.
47. Describe the role of negative feedback in the function of the parathyroid gland.
Answer
The production and secretion of PTH is regulated by a negative feedback loop. Low blood calcium levels initiate the production and secretion of PTH. PTH increases bone resorption, calcium absorption from the intestines, and calcium reabsorption by the kidneys. As a result, blood calcium levels begin to rise. This, in turn, inhibits the further production and secretion of PTH.
48. Explain why someone with a parathyroid gland tumor might develop kidney stones.
Answer
A parathyroid gland tumor can prompt hypersecretion of PTH. This can raise blood calcium levels so excessively that calcium deposits begin to accumulate throughout the body, including in
the kidney tubules, where they are referred to as kidney stones.
49. What are the three regions of the adrenal cortex and what hormones do they produce?
Answer
The outer region is the zona glomerulosa, which produces mineralocorticoids such as aldosterone; the next region is the zona fasciculata, which produces glucocorticoids such as cortisol; the inner region is the zona reticularis, which produces androgens.
50. If innervation to the adrenal medulla were disrupted, what would be the physiological outcome?
Answer
Damage to the innervation of the adrenal medulla would prevent the adrenal glands from responding to the hypothalamus during the fight-or-flight response. Therefore, the response would be reduced.
51. Compare and contrast the short-term and long-term stress response.
Answer
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The short-term stress response involves the hormones epinephrine and norepinephrine, which work to increase the oxygen supply to organs important for extreme muscular action such as the brain, lungs, and muscles. In the long-term stress response, the hormone cortisol is involved in catabolism of glycogen stores, proteins, and triglycerides, glucose and ketone synthesis, and downregulation of the immune system.
52. Seasonal affective disorder (SAD) is a mood disorder characterized by, among other symptoms, increased appetite, sluggishness, and increased sleepiness. It occurs most commonly during the winter months, especially in regions with long winter nights. Propose a role for melatonin in SAD and a possible non-drug therapy.
Answer
SAD is thought to occur in part because low levels and duration of sunlight allow excessive and prolonged secretion of melatonin. Light therapy—daytime exposure to very bright lighting—is one common therapy.
53. Retinitis pigmentosa (RP) is a disease that causes deterioration of the retinas of the eyes. Describe the impact RP would have on melatonin levels.
Answer
The retina is important for melatonin production because it senses light. Bright light inhibits the production of melatonin, whereas low light levels promote the production of melatonin. Therefore, deterioration of the retinas would most likely disturb the sleep-wake pattern because melatonin production would be elevated.
54. Compare and contrast the role of estrogens and progesterone.
Answer
Both estrogens and progesterone are steroid hormones produced by the ovaries that help regulate the menstrual cycle. Estrogens play an important role in the development of the female reproductive tract and secondary sex characteristics. They also help maintain pregnancy. Progesterone prepares the body for pregnancy and helps maintain pregnancy.
55. Describe the role of placental secretion of relaxin in preparation for childbirth.
Answer
Relaxin produced by the placenta is thought to soften and widen the pubic symphysis. This increases the size of the pelvic outlet, the birth canal through which the fetus passes during vaginal childbirth.
56. What would be the physiological consequence of a disease that destroyed the beta cells of the
pancreas?
Answer
The beta cells produce the hormone insulin, which is important in the regulation of blood glucose
levels. All insulin-dependent cells of the body require insulin in order to take up glucose from the bloodstream. Destruction of the beta cells would result in an inability to produce and secrete insulin, leading to abnormally high blood glucose levels and the disease called type 1 diabetes mellitus.
57. Why is foot care extremely important for people with diabetes mellitus?
Answer
Excessive blood glucose levels damage the blood vessels and nerves of the body’s extremities, increasing the risk for injury, infection, and tissue death. Loss of sensation to the feet means that a diabetic patient will not be able to feel foot trauma, such as from ill-fitting shoes. Even minor injuries commonly lead to infection, which, can progress to tissue death without proper care, requiring amputation.
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58. Summarize the role of GI tract hormones following a meal.
Answer
The presence of food in the GI tract stimulates the release of hormones that aid in digestion. For example, gastrin is secreted in response to stomach distention and causes the release of hydrochloric acid in the stomach. Secretin is secreted when acidic chyme enters the small intestine, and stimulates the release of pancreatic bicarbonate. In the presence of fat and protein in the duodenum, CCK stimulates the release of pancreatic digestive enzymes and bile from the gallbladder. Other GI tract hormones aid in glucose metabolism and other functions.
59. Compare and contrast the thymus gland in infancy and adulthood.
Answer
The thymus gland is important for the development and maturation of T cells. During infancy and early childhood, the thymus gland is large and very active, as the immune system is still developing. During adulthood, the thymus gland atrophies because the immune system is already
developed.
60. Distinguish between the effects of menopause and andropause on fertility
Answer
Menopause occurs as the result of a progressive decline in the function of the ovaries, resulting in low estrogen and progesterone levels. Ovulation ceases, and postmenopausal woman can no longer conceive a child. In contrast, andropause is a much more gradual and subtle decline in testosterone levels and functioning. A man typically maintains fertility until very old age, although the quantity, quality, and motility of the sperm he produces may be reduced.
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OpenStax Anatomy & Physiology Instructor Answer Guide
Anatomy & Physiology
Unit 4: Fluids and Transport
Chapter 18: The Cardiovascular System: Blood
Interactive Link Questions
1. Visit this site (http://openstaxcollege.org/l/normallevels) for a list of normal levels established for many of the substances found in a sample of blood. Serum, one of the specimen types included, refers to a sample of plasma after clotting factors have been removed. What types of measurements are given for levels of glucose in the blood?
Answer
There are values given for percent saturation, tension, and blood gas, and there are listings for different types of hemoglobin.
2. Watch this video (http://openstaxcollege.org/l/doping) to see doctors discuss the dangers of blood doping in sports. What are the some potential side effects of blood doping?
Answer
Side effects can include heart disease, stroke, pulmonary embolism, and virus transmission.
3. Figure 18.13 Are you able to recognize and identify the various formed elements? You will need to do this is a systematic manner, scanning along the image. The standard method is to use a grid, but this is not possible with this resource. Try constructing a simple table with each leukocyte type and then making a mark for each cell type you identify. Attempt to classify at least 50 and perhaps as many as 100 different cells. Based on the percentage of cells that you count, do the numbers represent a normal blood smear or does something appear to be abnormal?
Answer
This should appear to be a normal blood smear.
4. View these animations (http://openstaxcollege.org/l/coagulation) to explore the intrinsic, extrinsic, and common pathways that are involved the process of coagulation. The coagulation cascade restores hemostasis by activating coagulation factors in the presence of an injury. How does the endothelium of the blood vessel walls prevent the blood from coagulating as it flows through the blood vessels?
Answer
Clotting factors flow through the blood vessels in their inactive state. The endothelium does not have thrombogenic tissue factor to activate clotting factors.
Review Questions
5. Which of the following statements about blood is true?
Answer
C. Blood is slightly more viscous than water.
6. Which of the following statements about albumin is true?
Answer
B. It is the most abundant plasma protein.
7. Which of the following plasma proteins is not produced by the liver?
Answer
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D. immunoglobulin
8. Which of the formed elements arise from myeloid stem cells?
Answer
C. platelets
9. Which of the following statements about erythropoietin is true?
Answer
A. It facilitates the proliferation and differentiation of the erythrocyte lineage.
10. Interleukins are associated primarily with which of the following?
Answer
D. all of the above (production of various lymphocytes, immune response, inflammation)
11. Which of the following statements about mature, circulating erythrocytes is true?
Answer
A. They have no nucleus.
12. A molecule of hemoglobin ________.
Answer
C. consists of four globin proteins, each bound to a molecule of heme
13. The production of healthy erythrocytes depends upon the availability of ________.
Answer
D. copper, zinc, and vitamin B
12
14. Aging and damaged erythrocytes are removed from the circulation by ________.
Answer
C. macrophages
15. A patient has been suffering for 2 months with a chronic, watery diarrhea. A blood test is likely to reveal ________.
Answer
D. polycythemia
16. The process by which leukocytes squeeze through adjacent cells in a blood vessel wall is called ________.
Answer
C. emigration
17. Which of the following describes a neutrophil?
Answer
B. abundant, granular, especially effective against bacteria
18. T and B lymphocytes ________.
Answer
B. are involved with specific immune function
19. A patient has been experiencing severe, persistent allergy symptoms that are reduced when she takes an antihistamine. Before the treatment, this patient was likely to have had increased activity of which leukocyte?
Answer
A. basophils
20. Thrombocytes are more accurately called ________.
Answer
D. platelets
21. The first step in hemostasis is ________.
Answer
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A. vascular spasm
22. Prothrombin is converted to thrombin during the ________.
Answer
C. common pathway
23. Hemophilia is characterized by ________.
Answer
B. inadequate production of clotting factors
24. The process in which antibodies attach to antigens, causing the formation of masses of linked
cells, is called ________.
Answer
C. agglutination
25. People with ABO blood type O ________.
Answer
B. lack both antigens A and B on their erythrocytes
26. Hemolytic disease of the newborn is a risk during a subsequent pregnancy in which ________.
Answer
D. an Rh
−
mother is carrying a second Rh
+
fetus
Critical Thinking Questions
27. A patient’s hematocrit is 42 percent. Approximately what percentage of the patient’s blood is
plasma?
Answer
The patient’s blood is approximately 58 percent plasma (since the buffy coat is less than 1 percent).
28. Why would it be incorrect to refer to the formed elements as cells?
Answer
The formed elements include erythrocytes and leukocytes, which are cells (although mature erythrocytes do not have a nucleus); however, the formed elements also include platelets, which are not true cells but cell fragments.
29. True or false: The buffy coat is the portion of a blood sample that is made up of its proteins.
Answer
False. The buffy coat is the portion of blood that is made up of its leukocytes and platelets.
30. Myelofibrosis is a disorder in which inflammation and scar tissue formation in the bone marrow impair hemopoiesis. One sign is an enlarged spleen. Why?
Answer
When disease impairs the ability of the bone marrow to participate in hemopoiesis, extramedullary hemopoiesis begins in the patient’s liver and spleen. This causes the spleen to enlarge.
31. Would you expect a patient with a form of cancer called acute myelogenous leukemia to experience impaired production of erythrocytes, or impaired production of lymphocytes? Explain
your choice.
Answer
The adjective myelogenous suggests a condition originating from (generated by) myeloid cells. Acute myelogenous leukemia impairs the production of erythrocytes and other mature formed elements of the myeloid stem cell lineage. Lymphocytes arise from the lymphoid stem cell line.
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32. A young woman has been experiencing unusually heavy menstrual bleeding for several years. She follows a strict vegan diet (no animal foods). She is at risk for what disorder, and why?
Answer
She is at risk for anemia, because her unusually heavy menstrual bleeding results in excessive loss of erythrocytes each month. At the same time, her vegan diet means that she does not have dietary sources of heme iron. The non-heme iron she consumes in plant foods is not as well absorbed as heme iron.
33. A patient has thalassemia, a genetic disorder characterized by abnormal synthesis of globin proteins and excessive destruction of erythrocytes. This patient is jaundiced and is found to have an excessive level of bilirubin in his blood. Explain the connection.
Answer
Bilirubin is a breakdown product of the non-iron component of heme, which is cleaved from globin when erythrocytes are degraded. Excessive erythrocyte destruction would deposit excessive bilirubin in the blood. Bilirubin is a yellowish pigment, and high blood levels can manifest as yellowed skin
34. One of the more common adverse effects of cancer chemotherapy is the destruction of leukocytes. Before his next scheduled chemotherapy treatment, a patient undergoes a blood test called an absolute neutrophil count (ANC), which reveals that his neutrophil count is 1900 cells per microliter. Would his healthcare team be likely to proceed with his chemotherapy treatment? Why?
Answer
A neutrophil count below 1800 cells per microliter is considered abnormal. Thus, this patient’s ANC is at the low end of the normal range and there would be no reason to delay chemotherapy. In clinical practice, most patients are given chemotherapy if their ANC is above 1000.
35. A patient was admitted to the burn unit the previous evening suffering from a severe burn involving his left upper extremity and shoulder. A blood test reveals that he is experiencing leukocytosis. Why is this an expected finding?
Answer
Any severe stress can increase the leukocyte count, resulting in leukocytosis. A burn is especially
likely to increase the proliferation of leukocytes in order to ward off infection, a significant risk when the barrier function of the skin is destroyed.
36. A lab technician collects a blood sample in a glass tube. After about an hour, she harvests serum to continue her blood analysis. Explain what has happened during the hour that the sample
was in the glass tube.
Answer
When blood contacts glass, the intrinsic coagulation pathway is initiated. This leads to the common pathway, and the blood clots. Within about 30 minutes, the clot begins to shrink. After an hour, it is about half its original size. Its heavier weight will cause it to fall to the bottom of the tube during centrifugation, allowing the lab technician to harvest the serum remaining at the top.
37. Explain why administration of a thrombolytic agent is a first intervention for someone who has suffered a thrombotic stroke.
Answer
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In a thrombotic stroke, a blood vessel to the brain has been blocked by a thrombus, an aggregation of platelets and erythrocytes within a blood vessel. A thrombolytic agent is a medication that promotes the breakup of thrombi.
38. Following a motor vehicle accident, a patient is rushed to the emergency department with multiple traumatic injuries, causing severe bleeding. The patient’s condition is critical, and there is no time for determining his blood type. What type of blood is transfused, and why?
Answer
In emergency situations, blood type O
−
will be infused until cross matching can be done. Blood type O
−
is called the universal donor blood because the erythrocytes have neither A nor B antigens on their surface, and the Rh factor is negative.
39. In preparation for a scheduled surgery, a patient visits the hospital lab for a blood draw. The technician collects a blood sample and performs a test to determine its type. She places a sample of the patient’s blood in two wells. To the first well she adds anti-A antibody. To the second she adds anti-B antibody. Both samples visibly agglutinate. Has the technician made an error, or is this a normal response? If normal, what blood type does this indicate?
Answer
The lab technician has not made an error. Blood type AB has both A and B surface antigens, and neither anti-A nor anti-B antibodies circulating in the plasma. When anti-A antibodies (added to the first well) contact A antigens on AB erythrocytes, they will cause agglutination. Similarly, when anti-B antibodies contact B antigens on AB erythrocytes, they will cause agglutination.
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Anatomy & Physiology
Unit 4: Fluids and Transport
Chapter 19: The Cardiovascular System: The Heart
Interactive Link Questions
1. Visit this site (http://openstaxcollege.org/l/heartvalve) to observe an echocardiogram of actual heart valves opening and closing. Although much of the heart has been “removed” from this gif loop so the chordae tendineae are not visible, why is their presence more critical for the atrioventricular valves (tricuspid and mitral) than the semilunar (aortic and pulmonary) valves?
Answer
The pressure gradient between the atria and the ventricles is much greater than that between the ventricles and the pulmonary trunk and aorta. Without the presence of the chordae tendineae and papillary muscles, the valves would be blown back (prolapsed) into the atria and blood would regurgitate.
Review Questions
2. Which of the following is not important in preventing backflow of blood?
Answer
D. endocardium
3. Which valve separates the left atrium from the left ventricle?
Answer
A. mitral
4. Which of the following lists the valves in the order through which the blood flows from the vena cava through the heart?
Answer
A. tricuspid, pulmonary semilunar, bicuspid, aortic semilunar
5. Which chamber initially receives blood from the systemic circuit?
Answer
C. right atrium
6. The ________ layer secretes chemicals that help to regulate ionic environments and strength of contraction and serve as powerful vasoconstrictors.
Answer
B. endocardium
7. The myocardium would be the thickest in the ________.
Answer
B. left ventricle
8. In which septum is it normal to find openings in the adult?
Answer
C. atrioventricular septum
9. Which of the following is unique to cardiac muscle cells?
Answer
C. Only cardiac muscle is capable of autorhythmicity
10. The influx of which ion accounts for the plateau phase?
Answer
D. calcium
11. Which portion of the ECG corresponds to repolarization of the atria?
Answer
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D. none of the above: atrial repolarization is masked by ventricular depolarization
12. Which component of the heart conduction system would have the slowest rate of firing?
Answer
D. Purkinje fibers
13. The cardiac cycle consists of a distinct relaxation and contraction phase. Which term is typically used to refer ventricular contraction while no blood is being ejected?
Answer
D. isovolumic contraction
14. Most blood enters the ventricle during ________.
Answer
B. atrial diastole
15. The first heart sound represents which portion of the cardiac cycle?
Answer
C. closing of the atrioventricular valves
16. Ventricular relaxation immediately follows ________.
Answer
B. ventricular repolarization
17. The force the heart must overcome to pump blood is known as ________.
Answer
B. afterload
18. The cardiovascular centers are located in which area of the brain?
Answer
A. medulla oblongata
19. In a healthy young adult, what happens to cardiac output when heart rate increases above 160
bpm?
Answer
B. It decreases.
20. What happens to preload when there is venous constriction in the veins?
Answer
A. It increases.
21. Which of the following is a positive inotrope?
Answer
C. Ca
2+
22. The earliest organ to form and begin function within the developing human is the ________.
Answer
D. heart
23. Of the three germ layers that give rise to all adult tissues and organs, which gives rise to the heart?
Answer
C. mesoderm
24. The two tubes that eventually fuse to form the heart are referred to as the ________.
Answer
D. cardiogenic tubes
25. Which primitive area of the heart will give rise to the right ventricle?
Answer
A. bulbus cordis
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26. The pulmonary trunk and aorta are derived from which primitive heart structure?
Answer
D. truncus arteriosus
Critical Thinking Questions
27. Describe how the valves keep the blood moving in one direction.
Answer
When the ventricles contract and pressure begins to rise in the ventricles, there is an initial tendency for blood to flow back (regurgitate) to the atria. However, the papillary muscles also contract, placing tension on the chordae tendineae and holding the atrioventricular valves (tricuspid and mitral) in place to prevent the valves from prolapsing and being forced back into the atria. The semilunar valves (pulmonary and aortic) lack chordae tendineae and papillary muscles, but do not face the same pressure gradients as do the atrioventricular valves. As the ventricles relax and pressure drops within the ventricles, there is a tendency for the blood to flow
backward. However, the valves, consisting of reinforced endothelium and connective tissue, fill with blood and seal off the opening preventing the return of blood.
28. Why is the pressure in the pulmonary circulation lower than in the systemic circulation?
Answer
The pulmonary circuit consists of blood flowing to and from the lungs, whereas the systemic circuit carries blood to and from the entire body. The systemic circuit is far more extensive, consisting of far more vessels and offers much greater resistance to the flow of blood, so the heart must generate a higher pressure to overcome this resistance. This can be seen in the thickness of the myocardium in the ventricles.
29. Why is the plateau phase so critical to cardiac muscle function?
Answer
It prevents additional impulses from spreading through the heart prematurely, thereby allowing the muscle sufficient time to contract and pump blood effectively
30. How does the delay of the impulse at the atrioventricular node contribute to cardiac function?
Answer
It ensures sufficient time for the atrial muscle to contract and pump blood into the ventricles prior to the impulse being conducted into the lower chambers.
31. How do gap junctions and intercalated disks aid contraction of the heart?
Answer
Gap junctions within the intercalated disks allow impulses to spread from one cardiac muscle cell to another, allowing sodium, potassium, and calcium ions to flow between adjacent cells, propagating the action potential, and ensuring coordinated contractions.
32. Why do the cardiac muscles cells demonstrate autorhythmicity?
Answer
Without a true resting potential, there is a slow influx of sodium ions through slow channels that produces a prepotential that gradually reaches threshold.
33. Describe one cardiac cycle, beginning with both atria and ventricles relaxed.
Answer
The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0.8 seconds. Beginning with all chambers in diastole, blood flows passively from the veins into the atria and past the atrioventricular valves into the ventricles. The atria begin to contract following depolarization of the atria and pump blood into
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the ventricles. The ventricles begin to contract, raising pressure within the ventricles. When ventricular pressure rises above the pressure in the two major arteries, blood pushes open the two
semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax, and pressure within the ventricles drops. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart cycle.
34. Why does increasing EDV increase contractility?
Answer
Increasing EDV increases the sarcomeres’ lengths within the cardiac muscle cells, allowing more
cross bridge formation between the myosin and actin and providing for a more powerful contraction. This relationship is described in the Frank-Starling mechanism.
35. Why is afterload important to cardiac function?
Answer
Afterload represents the resistance within the arteries to the flow of blood ejected from the ventricles. If uncompensated, if afterload increases, flow will decrease. In order for the heart to maintain adequate flow to overcome increasing afterload, it must pump more forcefully. This is one of the negative consequences of high blood pressure or hypertension.
36. Why is it so important for the human heart to develop early and begin functioning within the developing embryo?
Answer
The human embryo is rapidly growing and has great demands for nutrients and oxygen, while producing waste products including carbon dioxide. All of these materials must be received from
or delivered to the mother for processing. Without an efficient early circulatory system, this would be impossible.
37. Describe how the major pumping chambers, the ventricles, form within the developing heart.
Answer
After fusion of the two endocardial tubes into the single primitive heart, five regions quickly become visible. From the head, these are the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus. Contractions propel the blood from the sinus venosus to the truncus arteriosus. About day 23, the heart begins to form an S-shaped structure within the pericardium. The bulbus cordis develops into the right ventricle, whereas the primitive
ventricle becomes the left ventricle. The interventricular septum separating these begins to form about day 28. The atrioventricular valves form between weeks five to eight. At this point, the heart ventricles resemble the adult structure.
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Anatomy & Physiology
Unit 4: Fluids and Transport
Chapter 20: The Cardiovascular System: Blood Vessels and Circulation
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/capillaryfunct) to explore capillaries and how they function in the body. Capillaries are never more than 100 micrometers away. What is the main component of interstitial fluid?
Answer
Water
2. Listen to this CDC podcast (http://openstaxcollege.org/l/CDCpodcast) to learn about hypertension, often described as a “silent killer.” What steps can you take to reduce your risk of a heart attack or stroke?
Answer
Take medications as prescribed, eat a healthy diet, exercise, and don’t smoke.
Review Questions
3. The endothelium is found in the ________.
Answer
A. tunica intima
4. Nervi vasorum control ________.
Answer
D. both vasoconstriction and vasodilation
5. Closer to the heart, arteries would be expected to have a higher percentage of ________.
Answer
C. elastic fibers
6. Which of the following best describes veins?
Answer
B. thin walled, large lumens, low pressure, have valves
7. An especially leaky type of capillary found in the liver and certain other tissues is called a ________.
Answer
C. sinusoid capillary
8. In a blood pressure measurement of 110/70, the number 70 is the ________.
Answer
B. diastolic pressure
9. A healthy elastic artery ________.
Answer
A. is compliant
10. Which of the following statements is true?
Answer
B. As blood volume decreases, blood pressure and blood flow also decrease.
11. Slight vasodilation in an arteriole prompts a ________.
Answer
D. huge decrease in resistance
12. Venoconstriction increases which of the following?
Answer
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D. all of the above (blood pressure within the vein, blood flow within the vein, and return of blood to the heart)
13. Hydrostatic pressure is ________.
Answer
B. the pressure exerted by fluid in an enclosed space
14. Net filtration pressure is calculated by ________.
Answer
D. subtracting the blood colloid osmotic pressure from the capillary hydrostatic pressure
15. Which of the following statements is true?
Answer
A. In one day, more fluid exits the capillary through filtration than enters through reabsorption.
16. Clusters of neurons in the medulla oblongata that regulate blood pressure are known collectively as ________.
Answer
D. the cardiovascular center
17. In the renin-angiotensin-aldosterone mechanism, ________.
Answer
C. aldosterone prompts the kidneys to reabsorb sodium
18. In the myogenic response, ________.
Answer
C. vascular smooth muscle responds to stretch
19. A form of circulatory shock common in young children with severe diarrhea or vomiting is ________.
Answer
A. hypovolemic shock
20. The coronary arteries branch off of the ________.
Answer
B. ascending aorta
21. Which of the following statements is true?
Answer
C. The radial and ulnar arteries join to form the palmar arch.
22. Arteries serving the stomach, pancreas, and liver all branch from the ________.
Answer
C. celiac trunk
23. The right and left brachiocephalic veins ________.
Answer
D. all of the above are true (drain blood from the right and left internal jugular veins, drain blood
from the right and left subclavian veins, and drain into the superior vena cava)
24. The hepatic portal system delivers blood from the digestive organs to the ________.
Answer
A. liver
25. Blood islands are ________.
Answer
D. masses of developing blood vessels and formed elements scattered throughout the embryonic disc
26. Which of the following statements is true?
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Answer
B. One umbilical vein carries oxygen-rich blood from the placenta to the fetal heart.
27. The ductus venosus is a shunt that allows ________.
Answer
C. most freshly oxygenated blood to flow into the fetal heart
Critical Thinking Questions
28. Arterioles are often referred to as resistance vessels. Why?
Answer
Arterioles receive blood from arteries, which are vessels with a much larger lumen. As their own lumen averages just 30 micrometers or less, arterioles are critical in slowing down—or resisting
—blood flow. The arterioles can also constrict or dilate, which varies their resistance, to help distribute blood flow to the tissues.
29. Cocaine use causes vasoconstriction. Is this likely to increase or decrease blood pressure, and
why?
Answer
Vasoconstriction causes the lumens of blood vessels to narrow. This increases the pressure of the
blood flowing within the vessel.
30. A blood vessel with a few smooth muscle fibers and connective tissue, and only a very thin tunica externa conducts blood toward the heart. What type of vessel is this?
Answer
This is a venule.
31. You measure a patient’s blood pressure at 130/85. Calculate the patient’s pulse pressure and mean arterial pressure. Determine whether each pressure is low, normal, or high.
Answer
The patient’s pulse pressure is 130 – 85 = 45 mm Hg. Generally, a pulse pressure should be at least 25 percent of the systolic pressure, but not more than 100 mm Hg. Since 25 percent of 130 = 32.5, the patient’s pulse pressure of 45 is normal. The patient’s mean arterial pressure is 85 + 1/3 (45) = 85 + 15 = 100. Normally, the mean arterial blood pressure falls within the range of 70 – 110 mmHg, so 100 is normal.
32. An obese patient comes to the clinic complaining of swollen feet and ankles, fatigue, shortness of breath, and often feeling “spaced out.” She is a cashier in a grocery store, a job that requires her to stand all day. Outside of work, she engages in no physical activity. She confesses that, because of her weight, she finds even walking uncomfortable. Explain how the skeletal muscle pump might play a role in this patient’s signs and symptoms.
Answer
People who stand upright all day and are inactive overall have very little skeletal muscle activity in the legs. Pooling of blood in the legs and feet is common. Venous return to the heart is reduced, a condition that in turn reduces cardiac output and therefore oxygenation of tissues throughout the body. This could at least partially account for the patient’s fatigue and shortness of breath, as well as her “spaced out” feeling, which commonly reflects reduced oxygen to the brain.
33. A patient arrives at the emergency department with dangerously low blood pressure. The patient’s blood colloid osmotic pressure is normal. How would you expect this situation to affect the patient’s net filtration pressure?
Answer
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The patient’s blood would flow more sluggishly from the arteriole into the capillary bed. Thus, the patient’s capillary hydrostatic pressure would be below the normal 35 mm Hg at the arterial end. At the same time, the patient’s blood colloidal osmotic pressure is normal—about 25 mm Hg. Thus, even at the arterial end of the capillary bed, the net filtration pressure would be below 10 mm Hg, and an abnormally reduced level of filtration would occur. In fact, reabsorption might begin to occur by the midpoint of the capillary bed.
34. True or false? The plasma proteins suspended in blood cross the capillary cell membrane and
enter the tissue fluid via facilitated diffusion. Explain your thinking.
Answer
False. The plasma proteins suspended in blood cannot cross the semipermeable capillary cell membrane, and so they remain in the plasma within the vessel, where they account for the blood colloid osmotic pressure.
35. A patient arrives in the emergency department with a blood pressure of 70/45 confused and complaining of thirst. Why?
Answer
This blood pressure is insufficient to circulate blood throughout the patient’s body and maintain adequate perfusion of the patient’s tissues. Ischemia would prompt hypoxia, including to the brain, prompting confusion. The low blood pressure would also trigger the renin-angiotensin-
aldosterone mechanism, and release of aldosterone would stimulate the thirst mechanism in the hypothalamus.
36. Nitric oxide is broken down very quickly after its release. Why?
Answer
Nitric oxide is a very powerful local vasodilator that is important in the autoregulation of tissue perfusion. If it were not broken down very quickly after its release, blood flow to the region could exceed metabolic needs.
37. Identify the ventricle of the heart that pumps oxygen depleted blood and the arteries of the body that carry oxygen-depleted blood.
Answer
The right ventricle of the heart pumps oxygen-depleted blood to the pulmonary arteries.
38. What organs do the gonadal veins drain?
Answer
The gonadal veins drain the testes in males and the ovaries in females.
39. What arteries play the leading roles in supplying blood to the brain?
Answer
The internal carotid arteries and the vertebral arteries provide most of the brain’s blood supply.
40. All tissues, including malignant tumors, need a blood supply. Explain why drugs called angiogenesis inhibitors would be used in cancer treatment.
Answer
Angiogenesis inhibitors are drugs that inhibit the growth of new blood vessels. They can impede the growth of tumors by limiting their blood supply and therefore their access to gas and nutrient exchange.
41. Explain the location and importance of the ductus arteriosus in fetal circulation.
Answer
The ductus arteriosus is a blood vessel that provides a passageway between the pulmonary trunk and the aorta during fetal life. Most blood ejected from the fetus’ right ventricle and entering the
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pulmonary trunk is diverted through this structure into the fetal aorta, thus bypassing the fetal lungs.
Anatomy & Physiology
Unit 4: Fluids and Transport
Chapter 21: The Lymphatic and Immune System
Interactive Link Questions
1. Visit this website (http://openstaxcollege.org/l/lymphsystem) for an overview of the lymphatic
system. What are the three main components of the lymphatic system?
Answer
The three main components are the lymph vessels, the lymph nodes, and the lymph.
2. Visit this website (http://openstaxcollege.org/l/immunecells) to learn about the many different cell types in the immune system and their very specialized jobs. What is the role of the dendritic cell in infection by HIV?
Answer
The dendritic cell transports the virus to a lymph node.
3. Visit this website (http://openstaxcollege.org/l/chemotaxis) to learn about phagocyte chemotaxis. Phagocyte chemotaxis is the movement of phagocytes according to the secretion of chemical messengers in the form of interleukins and other chemokines. By what means does a phagocyte destroy a bacterium that it has ingested?
Answer
The bacterium is digested by the phagocyte’s digestive enzymes (contained in its lysosomes).
4. Immunity can be acquired in an active or passive way, and it can be natural or artificial. Watch
this video (http://openstaxcollege.org/l/immunity) to see an animated discussion of passive and active immunity. What is an example of natural immunity acquired passively?
Answer
Breastfeeding is an example of natural immunity acquired passively.
Review Questions
5. Which of the following cells is phagocytic?
Answer
B. macrophage
6. Which structure allows lymph from the lower right limb to enter the bloodstream?
Answer
A. thoracic duct
7. Which of the following cells is important in the innate immune response?
Answer
C. macrophages
8. Which of the following cells would be most active in early, antiviral immune responses the first time one is exposed to pathogen?
Answer
D. natural killer cell
9. Which of the lymphoid nodules is most likely to see food antigens first?
Answer
A. tonsils
10. Which of the following signs is not characteristic of inflammation?
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Answer
C. cold
11. Which of the following is not important in the antiviral innate immune response?
Answer
D. microphages
12. Enhanced phagocytosis of a cell by the binding of a specific protein is called ________.
Answer
B. opsonization
13. Which of the following leads to the redness of inflammation?
Answer
C. increased blood flow
14. T cells that secrete cytokines that help antibody responses are called ________.
Answer
B. Th2
15. The taking in of antigen and digesting it for later presentation is called ________.
Answer
B. antigen processing
16. Why is clonal expansion so important?
Answer
D. to increase the numbers of specific cells
17. The elimination of self-reactive thymocytes is called ________.
Answer
B. negative selection.
18. Which type of T cell is most effective against viruses?
Answer
C. cytotoxic T cells
19. Removing functionality from a B cell without killing it is called ________.
Answer
D. clonal anergy
20. Which class of antibody crosses the placenta in pregnant women?
Answer
D. IgG
21. Which class of antibody has no known function other than as an antigen receptor?
Answer
D. IgD
22. When does class switching occur?
Answer
A. primary response
23. Which class of antibody is found in mucus?
Answer
B. IgA
24. Which enzymes in macrophages are important for clearing intracellular bacteria?
Answer
D. lysosomal
25. What type of chronic lung disease is caused by a Mycobacterium?
Answer
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C. tuberculosis
26. Which type of immune response is most directly effective against bacteria?
Answer
B. complement
27. What is the reason that you have to be immunized with a new influenza vaccine each year?
Answer
B. mutation
28. Which type of immune response works in concert with cytotoxic T cells against virally infected cells?
Answer
A. natural killer cells
29. Which type of hypersensitivity involves soluble antigen-antibody complexes?
Answer
C. type III
30. What causes the delay in delayed hypersensitivity?
Answer
C. recruitment of immune cells
31. Which of the following is a critical feature of immediate hypersensitivity?
Answer
D. histamine release
32. Which of the following is an autoimmune disease of the heart?
Answer
C. rheumatic fever
33. What drug is used to counteract the effects of anaphylactic shock?
Answer
A. epinephrine
34. Which of the following terms means “many genes”?
Answer
B. polygeny
35. Why do we have natural antibodies?
Answer
B. immunity to environmental bacteria
36. Which type of cancer is associated with HIV disease?
Answer
A. Kaposi’s sarcoma
37. How does cyclosporine A work?
Answer
B. suppresses T cells
38. What disease is associated with bone marrow transplants?
Answer
D. graft-versus-host disease
Critical Thinking Questions
39. Describe the flow of lymph from its origins in interstitial fluid to its emptying into the venous
bloodstream.
Answer
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The lymph enters through lymphatic capillaries, and then into larger lymphatic vessels. The lymph can only go in one direction due to valves in the vessels. The larger lymphatics merge to form trunks that enter into the blood via lymphatic ducts.
40. Describe the process of inflammation in an area that has been traumatized, but not infected.
Answer
The cell debris and damaged cells induce macrophages to begin to clean them up. Macrophages release cytokines that attract neutrophils, followed by more macrophages. Other mediators released by mast cells increase blood flow to the area and also vascular permeability, allowing the recruited cells to get from the blood to the site of infection, where they can phagocytose the dead cells and debris, preparing the site for wound repair.
41. Describe two early induced responses and what pathogens they affect.
Answer
Interferons are produced in virally infected cells and cause them to secrete signals for surrounding cells to make antiviral proteins. C-reactive protein is induced to be made by the liver
and will opsonize certain species of bacteria.
42. Describe the processing and presentation of an intracellular antigen.
Answer
The antigen is digested by the proteasome, brought into the endoplasmic reticulum by the TAP transporter system, where it binds to class I MHC molecules. These are taken to the cell surface by transport vesicles.
43. Describe clonal selection and expansion.
Answer
Antigen-specific clones are stimulated as their antigen receptor binds to antigen. They are then activated and proliferate, expanding their numbers. The result is a large number of antigen-
specific lymphocytes.
44. Describe how secondary B cell responses are developed.
Answer
B cells activated during a primary response differentiate either into terminally differentiated plasma cells or into memory B cells. These memory B cells are what respond during a secondary
or memory antibody response.
45. Describe the role of IgM in immunity.
Answer
IgM is an antigen receptor on naïve B cells. Upon activation, naïve B cells make IgM first. IgM is good at binding complement and thus has good antibacterial effects. IgM is replaced with other classes of antibodies later on in the primary response due to class switching.
46. Describe how seroconversion works in HIV disease.
Answer
Seroconversion is the clearance of virus in the serum due to the increase in specific serum antibody levels. Seroconversion happens in the early stages of HIV disease. Unfortunately, the antibody cannot completely clear the virus from the body and thus it most often progresses to AIDS.
47. Describe tuberculosis and the innocent bystander effect.
Answer
Tuberculosis is caused by bacteria resistant to lysosomal enzymes in alveolar macrophages, resulting in chronic infection. The immune response to these bacteria actually causes most of the lung damage that is characteristic of this life-threatening disease.
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48. Describe anaphylactic shock in someone sensitive to peanuts?
Answer
The peanuts cause high levels of mast cell degranulation in the throats of these individuals. The histamine released increases vascular permeability, causing edema and (swelling), making breathing difficult. This must be treated with epinephrine as soon as possible.
49. Describe rheumatic fever and how tolerance is broken.
Answer
Antibody response to the cell walls of β-Streptococcus cross-reacts with the heart muscle. Complement is then activated and the heart is damaged, leading to abnormal function. Tolerance is broken because heart myosin antigens are similar to antigens on the β- Streptococcus bacteria.
50. Describe how stress affects immune responses.
Answer
Stress causes the release of hormones and the activation of nerves that suppress the immune response. Short-term stress has little effect on the health of an already healthy individual, whereas chronic stress does lead to increases in disease in such people.
Anatomy & Physiology
Unit 5: Energy, Maintenance, and Environmental Exchange
Chapter 22: The Respiratory System
Interactive Link Questions
1. Visit this site (http://openstaxcollege.org/l/asthma) to learn more about what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma attack?
Answer
Inflammation and the production of a thick mucus; constriction of the airway muscles, or bronchospasm; and an increased sensitivity to allergens.
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2. Watch this video (http://openstaxcollege.org/l/spirometers) to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases
or determine the effectiveness of disease treatment.
Answer
Patients with respiratory ailments (such as asthma, emphysema, COPD, etc.) have issues with airway resistance and/or lung compliance. Both of these factors can interfere with the patient’s ability to move air effectively. A spirometry test can determine how much air the patient can move into and out of the lungs. If the air volumes are low, this can indicate that the patient has a respiratory disease or that the treatment regimen may need to be adjusted. If the numbers are normal, the patient does not have a significant respiratory disease or the treatment regimen is working as expected.
3. Watch this video (http://openstaxcollege.org/l/oxyblood) to see the transport of oxygen from the lungs to the tissues. Why is oxygenated blood bright red, whereas deoxygenated blood tends to be more of a purple color?
Answer
When oxygen binds to the hemoglobin molecule, oxyhemoglobin is created, which has a red color to it. Hemoglobin that is not bound to oxygen tends to be more of a blue–purple color. Oxygenated blood traveling through the systemic arteries has large amounts of oxyhemoglobin. As blood passes through the tissues, much of the oxygen is released into systemic capillaries. The deoxygenated blood returning through the systemic veins, therefore, contains much smaller amounts of oxyhemoglobin. The more oxyhemoglobin that is present in the blood, the redder the fluid will be. As a result, oxygenated blood will be much redder in color than deoxygenated blood.
Review Questions
4. Which of the following anatomical structures is not part of the conducting zone?
Answer
C. alveoli
5. What is the function of the conchae in the nasal cavity?
Answer
A. increase surface area
6. The fauces connects which of the following structures to the oropharynx?
Answer
D. oral cavity
7. Which of the following are structural features of the trachea?
Answer
D. all of the above
8. Which of the following structures is not part of the bronchial tree?
Answer
A. aveoli
9. What is the role of alveolar macrophages?
Answer
C. to remove pathogens and debris
10. Which of the following structures separates the lung into lobes?
Answer
B. fissure
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11. A section of the lung that receives its own tertiary bronchus is called the ________.
Answer
A. bronchopulmonary segment
12. The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the body.
Answer
C. respiratory
13. The pleura that surrounds the lungs consists of two layers, the ________.
Answer
A. visceral and parietal pleurae.
14. Which of the following processes does atmospheric pressure play a role in?
Answer
A. pulmonary ventilation
15. A decrease in volume leads to a(n) ________ pressure.
Answer
C. increase in
16. The pressure difference between the intra-alveolar and intrapleural pressures is called ________.
Answer
D. transpulmonary pressure
17. Gas flow decreases as ________ increases.
Answer
A. resistance
18. Contraction of the external intercostal muscles causes which of the following to occur?
Answer
D. The ribs and sternum move upward.
19. Which of the following prevents the alveoli from collapsing?
Answer
A. residual volume
20. Gas moves from an area of ________ partial pressure to an area of ________ partial pressure.
Answer
D. high; low
21. When ventilation is not sufficient, which of the following occurs?
Answer
A. The capillary constricts.
22. Gas exchange that occurs at the level of the tissues is called ________.
Answer
C. internal respiration
23. The partial pressure of carbon dioxide is 45 mm Hg in the blood and 40 mm Hg in the alveoli. What happens to the carbon dioxide?
Answer
B. It diffuses into the alveoli.
24. Oxyhemoglobin forms by a chemical reaction between which of the following?
Answer
C. hemoglobin and oxygen
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25. Which of the following factors play a role in the oxygen–hemoglobin saturation/dissociation curve?
Answer
D. all of the above (temperature, pH, BPG)
26. Which of the following occurs during the chloride shift?
Answer
B. Chloride is exchanged for bicarbonate.
27. A low partial pressure of oxygen promotes hemoglobin binding to carbon dioxide. This is an example of the ________.
Answer
A. Haldane effect
28. Increased ventilation that results in an increase in blood pH is called ________.
Answer
A. hyperventilation
29. Exercise can trigger symptoms of AMS due to which of the following?
Answer
D. small venous reserve of oxygen
30. Which of the following stimulates the production of erythrocytes?
Answer
D. erythropoietin
31. The olfactory pits form from which of the following?
Answer
C. ectoderm
32. A full complement of mature alveoli are present by ________.
Answer
A. early childhood, around 8 years of age
33. If a baby is born prematurely before type II cells produce sufficient pulmonary surfactant, which of the following might you expect?
Answer
B. difficulty inflating the lungs
34. When do fetal breathing movements begin?
Answer
A. around week 20
35. What happens to the fluid that remains in the lungs after birth?
Answer
C. . It is absorbed shortly after birth.
Critical Thinking Questions
36. Describe the three regions of the pharynx and their functions.
Answer
The pharynx has three major regions. The first region is the nasopharynx, which is connected to the posterior nasal cavity and functions as an airway. The second region is the oropharynx, which is continuous with the nasopharynx and is connected to the oral cavity at the fauces. The laryngopharynx is connected to the oropharynx and the esophagus and trachea. Both the oropharynx and laryngopharynx are passageways for air and food and drink
37. If a person sustains an injury to the epiglottis, what would be the physiological result?
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Answer
The epiglottis is a region of the larynx that is important during the swallowing of food or drink. As a person swallows, the pharynx moves upward and the epiglottis closes over the trachea, preventing food or drink from entering the trachea. If a person’s epiglottis were injured, this mechanism would be impaired. As a result, the person may have problems with food or drink entering the trachea, and possibly, the lungs. Over time, this may cause infections such as pneumonia to set in.
38. Compare and contrast the conducting and respiratory zones.
Answer
The conducting zone of the respiratory system includes the organs and structures that are not directly involved in gas exchange, but perform other duties such as providing a passageway for air, trapping and removing debris and pathogens, and warming and humidifying incoming air. Such structures include the nasal cavity, pharynx, larynx, trachea, and most of the bronchial tree. The respiratory zone includes all the organs and structures that are directly involved in gas exchange, including the respiratory bronchioles, alveolar ducts, and alveoli.
39. Compare and contrast the right and left lungs.
Answer
The right and left lungs differ in size and shape to accommodate other organs that encroach on the thoracic region. The right lung consists of three lobes and is shorter than the left lung, due to the position of the liver underneath it. The left lung consist of two lobes and is longer and narrower than the right lung. The left lung has a concave region on the mediastinal surface called
the cardiac notch that allows space for the heart.
40. Why are the pleurae not damaged during normal breathing?
Answer
There is a cavity, called the pleural cavity, between the parietal and visceral layers of the pleura. Mesothelial cells produce and secrete pleural fluid into the pleural cavity that acts as a lubricant. Therefore, as you breathe, the pleural fluid prevents the two layers of the pleura from rubbing against each other and causing damage due to friction.
41. Describe what is meant by the term “lung compliance.”
Answer
Lung compliance refers to the ability of lung tissue to stretch under pressure, which is determined in part by the surface tension of the alveoli and the ability of the connective tissue to stretch. Lung compliance plays a role in determining how much the lungs can change in volume, which in turn helps to determine pressure and air movement.
42. Outline the steps involved in quiet breathing.
Answer
Quiet breathing occurs at rest and without active thought. During quiet breathing, the diaphragm and external intercostal muscles work at different extents, depending on the situation. For inspiration, the diaphragm contracts, causing the diaphragm to flatten and drop towards the abdominal cavity, helping to expand the thoracic cavity. The external intercostal muscles contract as well, causing the rib cage to expand, and the rib cage and sternum to move outward, also expanding the thoracic cavity. Expansion of the thoracic cavity also causes the lungs to expand, due to the adhesiveness of the pleural fluid. As a result, the pressure within the lungs drops below that of the atmosphere, causing air to rush into the lungs. In contrast, expiration is a passive process. As the diaphragm and intercostal muscles relax, the lungs and thoracic tissues
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recoil, and the volume of the lungs decreases. This causes the pressure within the lungs to increase above that of the atmosphere, causing air to leave the lungs.
43. What is respiratory rate and how is it controlled?
Answer
Respiratory rate is defined as the number of breaths taken per minute. Respiratory rate is controlled by the respiratory center, located in the medulla oblongata. Conscious thought can alter the normal respiratory rate through control by skeletal muscle, although one cannot consciously stop the rate altogether. A typical resting respiratory rate is about 14 breaths per minute.
44. Compare and contrast Dalton’s law and Henry’s law.
Answer
Both Dalton’s and Henry’s laws describe the behavior of gases. Dalton’s law states that any gas in a mixture of gases exerts force as if it were not in a mixture. Henry’s law states that gas molecules dissolve in a liquid proportional to their partial pressure.
45. A smoker develops damage to several alveoli that then can no longer function. How does this
affect gas exchange?
Answer
The damaged alveoli will have insufficient ventilation, causing the partial pressure of oxygen in the alveoli to decrease. As a result, the pulmonary capillaries serving these alveoli will constrict, redirecting blood flow to other alveoli that are receiving sufficient ventilation.
46. Compare and contrast adult hemoglobin and fetal hemoglobin.
Answer
Both adult and fetal hemoglobin transport oxygen via iron molecules. However, fetal hemoglobin has about a 20-fold greater affinity for oxygen than does adult hemoglobin. This is due to a difference in structure; fetal hemoglobin has two subunits that have a slightly different structure than the subunits of adult hemoglobin.
47. Describe the relationship between the partial pressure of oxygen and the binding of oxygen to
hemoglobin.
Answer
The relationship between the partial pressure of oxygen and the binding of hemoglobin to oxygen is described by the oxygen–hemoglobin saturation/dissociation curve. As the partial pressure of oxygen increases, the number of oxygen molecules bound by hemoglobin increases, thereby increasing the saturation of hemoglobin.
48. Describe three ways in which carbon dioxide can be transported.
Answer
Carbon dioxide can be transported by three mechanisms: dissolved in plasma, as bicarbonate, or as carbaminohemoglobin. Dissolved in plasma, carbon dioxide molecules simply diffuse into the blood from the tissues. Bicarbonate is created by a chemical reaction that occurs mostly in erythrocytes, joining carbon dioxide and water by carbonic anhydrase, producing carbonic acid, which breaks down into bicarbonate and hydrogen ions. Carbaminohemoglobin is the bound form of hemoglobin and carbon dioxide
49. Describe the neural factors involved in increasing ventilation during exercise.
Answer
There are three neural factors that play a role in the increased ventilation observed during exercise. Because this increased ventilation occurs at the beginning of exercise, it is unlikely that
only blood oxygen and carbon dioxide levels are involved. The first neural factor is the
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psychological stimulus of making a conscious decision to exercise. The second neural factor is the stimulus of motor neuron activation by the skeletal muscles, which are involved in exercise. The third neural factor is activation of the proprioceptors located in the muscles, joints, and tendons that stimulate activity in the respiratory centers.
50. What is the major mechanism that results in acclimatization?
Answer
A major mechanism involved in acclimatization is the increased production of erythrocytes. A drop in tissue levels of oxygen stimulates the kidneys to produce the hormone erythropoietin, which signals the bone marrow to produce erythrocytes. As a result, individuals exposed to a high altitude for long periods of time have a greater number of circulating erythrocytes than do individuals at lower altitudes.
51. During what timeframe does a fetus have enough mature structures to breathe on its own if born prematurely? Describe the other structures that develop during this phase.
Answer
At about week 28, enough alveolar precursors have matured so that a baby born prematurely at this time can usually breathe on its own. Other structures that develop about this time are pulmonary capillaries, expanding to create a large surface area for gas exchange. Alveolar ducts and alveolar precursors have also developed.
52. Describe fetal breathing movements and their purpose.
Answer
Fetal breathing movements occur due to the contraction of respiratory muscles, causing the fetus to inhale and exhale amniotic fluid. It is thought that these movements are a way to “practice” breathing, which results in toning the muscles in preparation for breathing after birth. In addition,
fetal breathing movements may help alveoli to form and mature.
Anatomy & Physiology
Unit 5: Energy, Maintenance, and Environmental Exchange
Chapter 23: The Digestive System
Interactive Link Questions
1. By clicking on this link (http://openstaxcollege.org/l/fooddigestion) , you can watch a short video of what happens to the food you eat as it passes from your mouth to your intestine. Along the way, note how the food changes consistency and form. How does this change in consistency facilitate your gaining nutrients from food?
Answer
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Answers may vary.
2. Visit this site (http://openstaxcollege.org/l/fooddigestion2) for an overview of digestion of food in different regions of the digestive tract. Note the route of non-fat nutrients from the small intestine to their release as nutrients to the body.
Answer
Answers may vary.
3. Watch this animation (http://openstaxcollege.org/l/swallowing) to see how swallowing is a complex process that involves the nervous system to coordinate the actions of upper respiratory and digestive activities. During which stage of swallowing is there a risk of food entering respiratory pathways and how is this risk blocked?
Answer
Answers may vary.
4. Watch this animation (http://openstaxcollege.org/l/stomach1) that depicts the structure of the stomach and how this structure functions in the initiation of protein digestion. This view of the stomach shows the characteristic rugae. What is the function of these rugae?
Answer
Answers may vary.
5. Watch this animation (http://openstaxcollege.org/l/sintestine) that depicts the structure of the small intestine, and, in particular, the villi. Epithelial cells continue the digestion and absorption of nutrients and transport these nutrients to the lymphatic and circulatory systems. In the small intestine, the products of food digestion are absorbed by different structures in the villi. Which structure absorbs and transports fats?
Answer
Answers may vary.
6. By watching this animation (http://openstaxcollege.org/l/foodgroups), you will see that for the various food groups—proteins, fats, and carbohydrates—digestion begins in different parts of the
digestion system, though all end in the same place. Of the three major food classes (carbohydrates, fats, and proteins), which is digested in the mouth, the stomach, and the small intestine?
Answer
Answers may vary.
7. Watch this video (http://openstaxcollege.org/l/liver) to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and
wastes. At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?
Answer
Answers may vary.
Review Questions
8. Which of these organs is not considered an accessory digestive structure?
Answer
A. mouth
9. Which of the following organs is supported by a layer of adventitia rather than serosa?
Answer
A. esophagus
10. Which of the following membranes covers the stomach?
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Answer
D. visceral peritoneum
11. Which of these processes occurs in the mouth?
Answer
D. all of the above (ingestion, mechanical digestion, chemical digestion)
12. Which of these processes occurs throughout most of the alimentary canal?
Answer
B. propulsion
13. Which of the following stimuli activates sensors in the walls of digestive organs?
Answer
D. all of the above (breakdown products of digestion, distension, pH of chime)
14. Which of these statements about reflexes in the GI tract is false?
Answer
C.
Food that distends the stomach initiates long reflexes.
15. Which of these ingredients in saliva is responsible for activating salivary amylase?
Answer
C. chloride ions
16. Which of these statements about the pharynx is true?
Answer
B. The oropharynx is continuous superiorly with the nasopharynx.
17. Which structure is located where the esophagus penetrates the diaphragm?
Answer
A. esophageal hiatus
18. Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis?
Answer
D. esophageal phase
19. Which of these cells secrete hormones?
Answer
C. enteroendocrine cells
20. Where does the majority of chemical digestion in the stomach occur?
Answer
A. fundus and body
21. During gastric emptying, chyme is released into the duodenum through the ________.
Answer
D. pyloric sphincter
22. Parietal cells secrete ________.
Answer
B. hydrochloric acid
23. In which part of the alimentary canal does most digestion occur?
Answer
B. proximal small intestine
24. Which of these is most associated with villi?
Answer
B. lacteals
25. What is the role of the small intestine’s MALT?
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Answer
D. preventing bacteria from entering the bloodstream
26. Which part of the large intestine attaches to the appendix?
Answer
A. cecum
27. Which of these statements about bile is true?
Answer
D. Bile salts are recycled.
28. Pancreatic juice ________.
Answer
C. buffers chyme.
29. Where does the chemical digestion of starch begin?
Answer
A. mouth
30. Which of these is involved in the chemical digestion of protein?
Answer
B. trypsin
31. Where are most fat-digesting enzymes produced?
Answer
D. pancreas
32. Which of these nutrients is absorbed mainly in the duodenum?
Answer
B. iron
Critical Thinking Questions
33. Explain how the enteric nervous system supports the digestive system. What might occur that
could result in the autonomic nervous system having a negative impact on digestion?
Answer
The enteric nervous system helps regulate alimentary canal motility and the secretion of digestive juices, thus facilitating digestion. If a person becomes overly anxious, sympathetic innervation of the alimentary canal is stimulated, which can result in a slowing of digestive activity.
34. What layer of the alimentary canal tissue is capable of helping to protect the body against disease, and through what mechanism?
Answer
The lamina propria of the mucosa contains lymphoid tissue that makes up the MALT and responds to pathogens encountered in the alimentary canal.
35. Offer a theory to explain why segmentation occurs and peristalsis slows in the small intestine.
Answer
The majority of digestion and absorption occurs in the small intestine. By slowing the transit of chyme, segmentation and a reduced rate of peristalsis allow time for these processes to occur.
36. It has been several hours since you last ate. Walking past a bakery, you catch a whiff of freshly baked bread. What type of reflex is triggered, and what is the result?
Answer
The smell of food initiates long reflexes, which result in the secretion of digestive juices.
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37. The composition of saliva varies from gland to gland. Discuss how saliva produced by the parotid gland differs in action from saliva produced by the sublingual gland.
Answer
Parotid gland saliva is watery with little mucus but a lot of amylase, which allows it to mix freely
with food during mastication and begin the digestion of carbohydrates. In contrast, sublingual gland saliva has a lot of mucus with the least amount of amylase of all the salivary glands. The high mucus content serves to lubricate the food for swallowing.
38. During a hockey game, the puck hits a player in the mouth, knocking out all eight of his most
anterior teeth. Which teeth did the player lose and how does this loss affect food ingestion?
Answer
The incisors. Since these teeth are used for tearing off pieces of food during ingestion, the player will need to ingest foods that have already been cut into bite-sized pieces until the broken teeth are replaced.
39. What prevents swallowed food from entering the airways?
Answer
Usually when food is swallowed, involuntary muscle contractions cause the soft palate to rise and close off the nasopharynx. The larynx also is pulled up, and the epiglottis folds over the glottis. These actions block off the air passages.
40. Explain the mechanism responsible for gastroesophageal reflux.
Answer
If the lower esophageal sphincter does not close completely, the stomach’s acidic contents can back up into the esophagus, a phenomenon known as GERD.
41. Describe the three processes involved in the esophageal phase of deglutition.
Answer
Peristalsis moves the bolus down the esophagus and toward the stomach. Esophageal glands secrete mucus that lubricates the bolus and reduces friction. When the bolus nears the stomach, the lower esophageal sphincter relaxes, allowing the bolus to pass into the stomach.
42. Explain how the stomach is protected from self-digestion and why this is necessary.
Answer
The mucosal barrier protects the stomach from self-digestion. It includes a thick coating of bicarbonate-rich mucus; the mucus is physically protective, and bicarbonate neutralizes gastric acid. Epithelial cells meet at tight junctions, which block gastric juice from penetrating the underlying tissue layers, and stem cells quickly replace sloughed off epithelial mucosal cells.
43. Describe unique anatomical features that enable the stomach to perform digestive functions.
Answer
The stomach has an additional inner oblique smooth muscle layer that helps the muscularis churn
and mix food. The epithelium includes gastric glands that secrete gastric fluid. The gastric fluid consists mainly of mucous, HCl, and the enzyme pepsin released as pepsinogen.
44. Explain how nutrients absorbed in the small intestine pass into the general circulation.
Answer
Nutrients from the breakdown of carbohydrates and proteins are absorbed through a capillary bed in the villi of the small intestine. Lipid breakdown products are absorbed into a lacteal in the villi, and transported via the lymphatic system to the bloodstream.
45. Why is it important that chyme from the stomach is delivered to the small intestine slowly and in small amounts?
Answer
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OpenStax Anatomy & Physiology Instructor Answer Guide
If large quantities of chyme were forced into the small intestine, it would result in osmotic water loss from the blood into the intestinal lumen that could cause potentially life-threatening low blood volume and erosion of the duodenum.
46. Describe three of the differences between the walls of the large and small intestines.
Answer
The mucosa of the small intestine includes circular folds, villi, and microvilli. The wall of the large intestine has a thick mucosal layer, and deeper and more abundant mucus-secreting glands that facilitate the smooth passage of feces. There are three features that are unique to the large intestine: teniae coli, haustra, and epiploic appendages.
47. Why does the pancreas secrete some enzymes in their inactive forms, and where are these enzymes activated?
Answer
The pancreas secretes protein-digesting enzymes in their inactive forms. If secreted in their active forms, they would self-digest the pancreas. These enzymes are activated in the duodenum.
48. Describe the location of hepatocytes in the liver and how this arrangement enhances their function.
Answer
The hepatocytes are the main cell type of the liver. They process, store, and release nutrients into
the blood. Radiating out from the central vein, they are tightly packed around the hepatic sinusoids, allowing the hepatocytes easy access to the blood flowing through the sinusoids.
49. Explain the role of bile salts and lecithin in the emulsification of lipids (fats).
Answer
Bile salts and lecithin can emulsify large lipid globules because they are amphipathic; they have a nonpolar (hydrophobic) region that attaches to the large fat molecules as well as a polar (hydrophilic) region that interacts with the watery chime in the intestine.
50. How is vitamin B
12
absorbed?
Answer
Intrinsic factor secreted in the stomach binds to the large B
12
compound, creating a combination that can bind to mucosal receptors in the ileum.
Anatomy & Physiology
Unit 5: Energy, Maintenance, and Environmental Exchange
Chapter 24: Metabolism and Nutrition
Review Questions
1. A monosaccharide is formed from a polysaccharide in what kind of reaction?
Answer
C. catabolic reaction
2. If anabolic reactions exceed catabolic reactions, the result will be ________.
Answer
B. weight gain
3. When NAD becomes NADH, the coenzyme has been ________.
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Answer
A. reduced
4. Anabolic reactions use energy by ________.
Answer
B. removing a phosphate group from ATP
5. Glycolysis results in the production of two ________ molecules from a single molecule of glucose. In the absence of ________, the end product of glycolysis is ________.
Answer
C. pyruvate, oxygen, lactate
6. The Krebs cycle converts ________ through a cycle of reactions. In the process, ATP, ________, and ________ are produced.
Answer
B. acetyl CoA; FADH
2
; NADH
7. Which pathway produces the most ATP molecules?
Answer
C. the electron transport chain
8. Aerobic cellular respiration results in the production of these two products.
Answer
D. ATP and H
2
O
9. When NAD
+
becomes NADH, the coenzyme has been ________.
Answer
A. reduced
10. Lipids in the diet can be ________.
Answer
D. all of the above (broken down into energy for the body, stored as triglycerides for later use, converted into acetyl CoA)
11. The gallbladder provides ________ that aid(s) in transport of lipids across the intestinal membrane.
Answer
D. bile salts
12. Triglycerides are transported by chylomicrons because ________.
Answer
A. they cannot move easily in the blood stream because they are fat based, while the blood is water based
13. Which molecule produces the most ATP?
Answer
C. triglycerides
14. Which molecules can enter the Krebs cycle?
Answer
B. acetyl CoA
15. Acetyl CoA can be converted to all of the following except ________.
Answer
C. polysaccharides
16. Digestion of proteins begins in the ________ where ________ and ________ mix with food to break down protein into ________.
Answer
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D. stomach; pepsin; HCl; amino acids
17. Amino acids are needed to ________.
Answer
A. build new proteins
18. If an amino acid is not used to create new proteins, it can be ________.
Answer
B. converted to glucose or ketones
19. During the absorptive state, glucose levels are ________, insulin levels are ________, and glucagon levels ________.
Answer
D. high; high; are low
20. Starvation sets in after 3 to 4 days without food. Which hormones change in response to low glucose levels?
Answer
A. glucagon and insulin
21. The postabsorptive state relies on stores of ________ in the ________.
Answer
C. glycogen; liver
22. The body’s temperature is controlled by the ________. This temperature is always kept between ________.
Answer
B. hypothalamus; 97.7–99.5 °F
23. Fever increases the body temperature and can induce chills to help cool the temperature back down. What other mechanisms are in place to regulate the body temperature?
Answer
D. all of the above (shivering, sweating, erection of the hairs on the arms and legs)
24. The heat you feel on your chair when you stand up was transferred from your skin via ________.
Answer
A. conduction
25. A crowded room warms up through the mechanism of ________.
Answer
C. radiation
26. A deficiency in vitamin A can result in ________.
Answer
C. improper eye development or sight
27. Rickets results in improper bone development in children that arises from the malabsorption of calcium and a deficiency in ________.
Answer
A. vitamin D
28. Consuming which type of food will help the most with weight loss?
Answer
C. lean meats
29. Which of the following is stored in the body?
Answer
B. phosphorous
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Critical Thinking Questions
30. Describe how metabolism can be altered.
Answer
An increase or decrease in lean muscle mass will result in an increase or decrease in metabolism.
31. Describe how Addison’s disease can be treated.
Answer
Addison’s disease is characterized by low cortisol levels. One way to treat the disease is by giving cortisol to the patient.
32. Explain how glucose is metabolized to yield ATP.
Answer
Glucose is oxidized during glycolysis, creating pyruvate, which is processed through the Krebs cycle to produce NADH, FADH2, ATP, and CO
2
. The FADH
2
and NADH yield ATP.
33. Insulin is released when food is ingested and stimulates the uptake of glucose into the cell. Discuss the mechanism cells employ to create a concentration gradient to ensure continual uptake of glucose from the bloodstream.
Answer
Upon entry into the cell, hexokinase or glucokinase phosphorylates glucose, converting it into glucose-6-phosphate. In this form, glucose-6-phosphate is trapped in the cell. Because all of the glucose has been phosphorylated, new glucose molecules can be transported into the cell according to its concentration gradient.
34. Discuss how carbohydrates can be stored as fat.
Answer
Carbohydrates are converted into pyruvate during glycolysis. This pyruvate is converted into acetyl CoA and proceeds through the Krebs cycle. When excess acetyl CoA is produced that cannot be processed through the Krebs cycle, the acetyl CoA is converted into triglycerides and fatty acids to be stored in the liver and adipose tissue.
35. If a diabetic’s breath smells like alcohol, what could this mean?
Answer
If diabetes is uncontrolled, the glucose in the blood is not being taken up and processed by the cells. Although blood glucose levels are high, there is no glucose available to the cells to be converted into energy. Because glucose is lacking, the body turns to other energy sources, including ketones. A side effect of using ketones as fuel is a sweet alcohol smell on the breath.
36. Amino acids are not stored in the body. Describe how excess amino acids are processed in the cell.
Answer
Amino acids are not stored in the body. The individual amino acids are broken down into pyruvate, acetyl CoA, or intermediates of the Krebs cycle, and used for energy or for lipogenesis reactions to be stored as fats.
37. Release of trypsin and chymotrypsin in their active form can result in the digestion of the pancreas or small intestine itself. What mechanism does the body employ to prevent its self-
destruction?
Answer
Trypsin and chymotrypsin are released as inactive proenzymes. They are only activated in the small intestine, where they act upon ingested proteins in the food. This helps avoid unintended breakdown of the pancreas or small intestine.
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38. In type II diabetes, insulin is produced but is nonfunctional. These patients are described as “starving in a sea of plenty,” because their blood glucose levels are high, but none of the glucose is transported into the cells. Describe how this leads to malnutrition.
Answer
Insulin stimulates the uptake of glucose into the cells. In diabetes, the insulin does not function properly; therefore, the blood glucose is unable to be transported across the cell membrane for processing. These patients are unable to process the glucose in their blood and therefore must rely on other sources of fuel. If the disease is not controlled properly, this inability to process the glucose can lead to starvation states even though the patient is eating.
39. Ketone bodies are used as an alternative source of fuel during starvation. Describe how ketones are synthesized.
Answer
When triglycerides and fatty acids are broken down, acetyl CoA is created. If excess acetyl CoA is generated in this process, the excess is used in ketogenesis or the creation of ketones. This creation results from the conversion of acetyl CoA by thiolase into acetoacetyl CoA. This acetoacetyl CoA is subsequently converted into β-hydroxybutyrate, the most common ketone in the body
40. How does vasoconstriction help increase the core temperature of the body?
Answer
When blood flows to the outer layers of the skin or to the extremities, heat is lost to the environment by the mechanisms of conduction, convection, or radiation. This will cool the blood
and the body. Vasoconstriction helps increase the core body temperature by preventing the flow of blood to the outer layer of the skin and outer parts of the extremities.
41. How can the ingestion of food increase the body temperature?
Answer
The ingestion of food stimulates digestion and processing of the carbohydrates, proteins, and fats. This breakdown of food triggers glycolysis, the Krebs cycle, the electron transport chain, fatty acid oxidation, lipogenesis, and amino acid oxidation to produce energy. Heat is a byproduct of those reactions.
42. Weight loss and weight gain are complex processes. What are some of the main factors that influence weight gain in people?
Answer
Factors that influence weight gain are food intake (both quantity and quality), environmental factors, height, exercise level, some drugs or disease states, and genes.
43. Some low-fat or non-fat foods contain a large amount of sugar to replace the fat content of the food. Discuss how this leads to increased fat in the body (and weight gain) even though the item is non-fat.
Answer
Although these foods technically do not have fat added, many times a significant amount of sugar is added to sweeten the food and make it taste better. These foods are non-fat; however, they can lead to significant fat storage or weight gain because the excess sugar is broken down into pyruvate, but overloads the Krebs cycle. When this happens, the sugar is converted into fat through lipogenesis and stored in adipose tissues.
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Anatomy & Physiology
Unit 5: Energy, Maintenance, and Environmental Exchange
Chapter 25: The Urinary System
Review Questions
1. Diabetes insipidus or diabetes mellitus would most likely be indicated by ________.
Answer
B. polyuria
2. The color of urine is determined mainly by ________.
Answer
C. byproducts of red blood cell breakdown
3. Production of less than 50 mL/day of urine is called ________.
Answer
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D. anuria
4. Peristaltic contractions occur in the ________.
Answer
C. ureters
5. Somatic motor neurons must be ________ to relax the external urethral sphincter to allow urination.
Answer
B. inhibited
6. Which part of the urinary system is not completely retroperitoneal?
Answer
C. bladder
7. The renal pyramids are separated from each other by extensions of the renal cortex called ________.
Answer
D. renal columns
8. The primary structure found within the medulla is the ________.
Answer
A. loop of Henle
9. The right kidney is slightly lower because ________.
Answer
A. it is displaced by the liver
10. Blood filtrate is captured in the lumen of the ________.
Answer
B. Bowman’s capsule
11. What are the names of the capillaries following the efferent arteriole?
Answer
C. peritubular and vasa recta
12. The functional unit of the kidney is called ________.
Answer
C. the nephron
13. ________ pressure must be greater on the capillary side of the filtration membrane to achieve
filtration.
Answer
B. Hydrostatic
14. Production of urine to modify plasma makeup is the result of ________.
Answer
D. filtration, absorption, and secretion
15. Systemic blood pressure must stay above 60 so that the proper amount of filtration occurs.
Answer
B. false
16. Aquaporin channels are only found in the collecting duct.
Answer
B. false
17. Most absorption and secretion occurs in this part of the nephron.
Answer
A. proximal convoluted tubule
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18. The fine tuning of water recovery or disposal occurs in ________.
Answer
B. the collecting ducts
19. Vasodilation of blood vessels to the kidneys is due to ________.
Answer
B. less frequent action potentials
20. When blood pressure increases, blood vessels supplying the kidney will ________ to mount a
steady rate of filtration.
Answer
A. contract
21. Which of these three paracrine chemicals cause vasodilation?
Answer
C. nitric oxide
22. What hormone directly opposes the actions of natriuretic hormones?
Answer
D. aldosterone
23. Which of these is a vasoconstrictor?
Answer
D. angiotensin II
24. What signal causes the heart to secrete atrial natriuretic hormone?
Answer
A. increased blood pressure
25. Which of these beverages does not have a diuretic effect?
Answer
D. milk
26. Progesterone can bind to receptors for which hormone that, when released, activates water retention?
Answer
A. aldosterone
27. Renin is released in response to ________.
Answer
B. decreased blood pressure
28. Which step in vitamin D production does the kidney perform?
Answer
B. converts calcidiol into calcitriol
29. Which hormone does the kidney produce that stimulates red blood cell production?
Answer
C. EPO
30. If there were no aquaporin channels in the collecting duct, ________.
Answer
D. you would suffer severe dehydration
Critical Thinking Questions
31. What is suggested by the presence of white blood cells found in the urine?
Answer
The presence of white blood cells found in the urine suggests urinary tract infection.
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32. Both diabetes mellitus and diabetes insipidus produce large urine volumes, but how would other characteristics of the urine differ between the two diseases?
Answer
Diabetes mellitus would result in urine containing glucose, and diabetes insipidus would produce
urine with very low osmolarity (low specific gravity, dilute).
33. Why are females more likely to contract bladder infections than males?
Answer
The longer urethra of males means bacteria must travel farther to the bladder to cause an infection.
34. Describe how forceful urination is accomplished.
Answer
Forceful urination is accomplished by contraction of abdominal muscles.
35. What anatomical structures provide protection to the kidney?
Answer
Retroperitoneal anchoring, renal fat pads, and ribs provide protection to the kidney.
36. How does the renal portal system differ from the hypothalamo–hypophyseal and digestive portal systems?
Answer
The renal portal system has an artery between the first and second capillary bed. The others have a vein.
37. Name the structures found in the renal hilum.
Answer
The structures found in the renal hilum are arteries, veins, ureters, lymphatics, and nerves.
38. Which structures make up the renal corpuscle?
Answer
The structures that make up the renal corpuscle are the glomerulus, Bowman’s capsule, and PCT.
39. What are the major structures comprising the filtration membrane?
Answer
The major structures comprising the filtration membrane are fenestrations and podocyte fenestra,
fused basement membrane, and filtration slits.
40. Give the formula for net filtration pressure.
Answer
Net filtration pressure (NFP) = glomerular blood hydrostatic pressure (GBHP) – [capsular hydrostatic pressure (CHP) + blood colloid osmotic pressure (BCOP)]
41. Name at least five symptoms of kidney failure.
Answer
Symptoms of kidney failure are weakness, lethargy, shortness of breath, widespread edema, anemia, metabolic acidosis or alkalosis, heart arrhythmias, uremia, loss of appetite, fatigue, excessive urination, and oliguria.
42. Which vessels and what part of the nephron are involved in countercurrent multiplication?
Answer
The vasa recta and loop of Henle are involved in countercurrent multiplication.
43. Give the approximate osmolarity of fluid in the proximal convoluted tubule, deepest part of the loop of Henle, distal convoluted tubule, and the collecting ducts.
Answer
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The approximate osmolarities are: CT = 300; deepest loop = 1200; DCT = 100; and collecting ducts = 100–1200.
44. Explain what happens to Na
+
concentration in the nephron when GFR increases.
Answer
Sodium concentration in the filtrate increases when GFR increases; it will decrease when GFR decreases.
45. If you want the kidney to excrete more Na
+
in the urine, what do you want the blood flow to do?
Answer
To excrete more Na
+
in the urine, increase the flow rate.
46. What organs produce which hormones or enzymes in the renin–angiotensin system?
Answer
The liver produces angiotensinogen, the lungs produce ACE, and the kidneys produce renin.
47. PTH affects absorption and reabsorption of what?
Answer
PTH affects absorption and reabsorption of calcium.
48. Why is ADH also called vasopressin?
Answer
When first discovered, it was named for its known activity—vasoconstriction.
49. How can glucose be a diuretic?
Answer
In cases of diabetes mellitus, there is more glucose present than the kidney can recover and the excess glucose is lost in the urine. It possesses osmotic character so that it attracts water to the forming urine.
50. How does lack of protein in the blood cause edema?
Answer
Protein has osmotic properties. If there is not enough protein in the blood, water will be attracted to the interstitial space and the cell cytoplasm resulting in tissue edema.
51. Which three electrolytes are most closely regulated by the kidney?
Answer
The three electrolytes are most closely regulated by the kidney are calcium, sodium, and potassium.
Anatomy & Physiology
Unit 5: Energy, Maintenance, and Environmental Exchange
Chapter 26: Fluid, Electrolyte, and Acid-Base Balance
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/bodyfluids) to learn more about body fluids, fluid compartments, and electrolytes. When blood volume decreases due to sweating, from what source is water taken in by the blood?
Answer
The interstitial fluid (IF).
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2. Watch this video (http://openstaxcollege.org/l/dynamicfluid) to see an explanation of the dynamics of fluid in the body’s compartments. What happens in tissues when capillary blood pressure is less than osmotic pressure?
Answer
Fluid enters the capillaries from interstitial spaces.
3. Watch this video (http://openstaxcollege.org/l/saltwater) to see an explanation of the effect of seawater on humans. What effect does drinking seawater have on the body?
Answer
Drinking seawater dehydrates the body as the body must pass sodium through the kidneys, and water follows.
4. Watch this video (http://openstaxcollege.org/l/altitude) to see a demonstration of the effect altitude has on blood pH. What effect does high altitude have on blood pH, and why?
Answer
Because oxygen is reduced, the respiratory rate increases to accommodate, and hyperventilation removes CO2 faster than normal, resulting in alkalosis.
Review Questions
5. Solute contributes to the movement of water between cells and the surrounding medium by ________.
Answer
A. osmotic pressure
6. A cation has a(n) ________ charge.
Answer
B. positive
7. Interstitial fluid (IF) is ________.
Answer
C. the fluid that bathes all of the body’s cells except for blood cells
8. The largest amount of water comes into the body via ________.
Answer
C. liquids
9. The largest amount of water leaves the body via ________.
Answer
D. urine
10. Insensible water loss is water lost via ________.
Answer
A. skin evaporation and in air from the lungs
11. How soon after drinking a large glass of water will a person start increasing their urine output?
Answer
B. 30 minutes
12. Bone serves as a mineral reserve for which two ions?
Answer
B. calcium and phosphate
13. Electrolytes are lost mostly through ________.
Answer
A. renal function
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14. The major cation in extracellular fluid is ________.
Answer
A. sodium
15. The major cation in intracellular fluid is ________.
Answer
B. potassium
16. The major anion in extracellular fluid is ________.
Answer
C. chloride
17. Most of the body’s calcium is found in ________.
Answer
B. bone
18. Abnormally increased blood levels of sodium are termed ________.
Answer
C. hypernatremia
19. The ion with the lowest blood level is ________.
Answer
B. potassium
20. Which two ions are most affected by aldosterone?
Answer
A. sodium and potassium
21. Which of the following is the most important buffer inside red blood cells?
Answer
B. hemoglobin
22. Which explanation best describes why plasma proteins can function as buffers?
Answer
C. Proteins have both positive and negative charges on their surface.
23. The buffer that is adjusted to control acid-base balance is ________.
Answer
D. bicarbonate: carbonic acid buffer
24. Carbonic acid levels are controlled through the ________.
Answer
A. respiratory system
25. Bicarbonate ion concentrations in the blood are controlled through the ________.
Answer
B. renal system
26. Which reaction is catalyzed by carbonic anhydrase?
Answer
B. CO
2
+ H
2
O ↔ H
2
CO
3
27. Which of the following is a cause of metabolic acidosis?
Answer
C. diarrhea
28. Which of the following is a cause of respiratory acidosis?
Answer
A. emphysema
29. At a pH of 7.40, the carbonic acid ratio is ________.
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Answer
C. 20:1
30. Which of the following is characterized as metabolic alkalosis?
Answer
B. increased pH, increased pCO
2
, increased HCO
3
-
Critical Thinking Questions
31. Plasma contains more sodium than chloride. How can this be if individual ions of sodium and
chloride exactly balance each other out, and plasma is electrically neutral?
Answer
There are additional negatively charged molecules in plasma besides chloride. The additional sodium balances the total negative charges.
32. How is fluid moved from compartment to compartment?
Answer
Fluid is moved by a combination of osmotic and hydrostatic pressures. The osmotic pressure results from differences in solute concentrations across cell membranes. Hydrostatic pressure results from the pressure of blood as it enters a capillary system, forcing some fluid out of the vessel into the surrounding tissues.
33. Describe the effect of ADH on renal collecting tubules.
Answer
ADH constricts the arterioles in the peripheral circulation, limiting blood to the extremities and increasing the blood supply to the core of the body. ADH also causes the epithelial cells lining the renal collecting tubules to move water channel proteins called aquaporins from the sides of the cells to the apical surface. This greatly increases the passage of water from the renal filtrate through the wall of the collecting tubule as well as the reabsorption of water into the bloodstream.
34. Why is it important for the amount of water intake to equal the amount of water output?
Answer
Any imbalance of water entering or leaving the body will create an osmotic imbalance that will adversely affect cell and tissue function.
35. Explain how the CO
2
generated by cells and exhaled in the lungs is carried as bicarbonate in the blood.
Answer
Very little of the carbon dioxide in the blood is carried dissolved in the plasma. It is transformed into carbonic acid and then into bicarbonate in order to mix in plasma for transportation to the lungs, where it reverts back to its gaseous form.
36. How can one have an imbalance in a substance, but not actually have elevated or deficient levels of that substance in the body?
Answer
Without having an absolute excess or deficiency of a substance, one can have too much or too little of that substance in a given compartment. Such a relative increase or decrease is due to a redistribution of water or the ion in the body’s compartments. This may be due to the loss of water in the blood, leading to a hemoconcentration or dilution of the ion in tissues due to edema.
37. Describe the conservation of bicarbonate ions in the renal system.
Answer
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Bicarbonate ions are freely filtered through the glomerulus. They cannot pass freely into the renal tubular cells and must be converted into CO
2
in the filtrate, which can pass through the cell membrane. Sodium ions are reabsorbed at the membrane, and hydrogen ions are expelled into the filtrate. The hydrogen ions combine with bicarbonate, forming carbonic acid, which dissociates into CO
2
gas and water. The gas diffuses into the renal cells where carbonic anhydrase catalyzes its conversion back into a bicarbonate ion, which enters the blood.
38. Describe the control of blood carbonic acid levels through the respiratory system.
Answer
Carbonic acid blood levels are controlled through the respiratory system by the expulsion of CO
2
from the lungs. The formula for the production of bicarbonate ions is reversible if the concentration of CO
2
decreases. As this happens in the lungs, carbonic acid is converted into a gas, and the concentration of the acid decreases. The rate of respiration determines the amount of
CO
2
exhaled. If the rate increases, less acid is in the blood; if the rate decreases, the blood can become more acidic.
39. Case Study: Bob is a 64-year-old male admitted to the emergency room for asthma. His laboratory results are as follows: pH 7.31, pCO
2
higher than normal, and total HCO
3
–
also higher
than normal. Classify his acid-base balance as acidosis or alkalosis, and as metabolic or respiratory. Is there evidence of compensation? Propose the mechanism by which asthma contributed to the lab results seen.
Answer
Respiratory acidosis is present as evidenced by the decreased pH and increased pCO
2
, with some compensation as shown by the increased total HCO
3
– . His asthma has compromised his respiratory functions, and excess CO
2
is being retained in his blood.
40. Case Study: Kim is a 38-year-old women admitted to the hospital for bulimia. Her laboratory
results are as follows: pH 7.48, pCO
2
in the normal range, and total HCO
3
–
higher than normal. Classify her acid-base balance as acidosis or alkalosis, and as metabolic or respiratory. Is there evidence of compensation? Propose the mechanism by which bulimia contributed to the lab results seen.
Answer
Metabolic alkalosis is present as evidenced by the increased pH and increased HCO
3
–
, without compensation as seen in the normal pCO
2
. The bulimia has caused excessive loss of hydrochloric
acid from the stomach and a loss of hydrogen ions from the body, resulting in an excess of bicarbonate ions in the blood.
Anatomy & Physiology
Unit 6: Human Development and the Continuity of Life
Chapter 27: The Reproductive System
Interactive Link Questions
1. Watch this video (http://openstaxcollege.org/l/vasectomy) to learn about vasectomy. As described in this video, a vasectomy is a procedure in which a small section of the ductus (vas) deferens is removed from the scrotum. This interrupts the path taken by sperm through the ductus deferens. If sperm do not exit through the vas, either because the man has had a vasectomy or has not ejaculated, in what region of the testis do they remain?
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Answer
Sperm remain in the epididymis until they degenerate.
2. Watch this video (http://openstaxcollege.org/l/spermpath) to explore the structures of the male reproductive system and the path of sperm that starts in the testes and ends as the sperm leave the
penis through the urethra. Where are sperm deposited after they leave the ejaculatory duct?
Answer
Sperm enter the prostate.
3. Watch this video (http://openstaxcollege.org/l/ovulation) to observe ovulation and its initiation
in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube?
Answer
The fimbriae sweep the oocyte into the uterine tube.
4. Watch this series of videos (http://openstaxcollege.org/l/oocyte) to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation?
Answer
The oocyte may not enter the tube and may enter the pelvic cavity.
5. A baby’s gender is determined at conception, and the different genitalia of male and female fetuses develop from the same tissues in the embryo. View this animation (http://openstaxcollege.org/l/fetus) that compares the development of structures of the female and male reproductive systems in a growing fetus. Where are the testes located for most of gestational time?
Answer
The testes are located in the abdomen.
Review Questions
6. What are male gametes called?
Answer
B. sperm
7. Leydig cells ________.
Answer
A. secrete testosterone
8. Which hypothalamic hormone contributes to the regulation of the male reproductive system?
Answer
B. gonadotropin-releasing hormone
9. What is the function of the epididymis?
Answer
A. sperm maturation and storage
10. Spermatogenesis takes place in the ________.
Answer
C. seminiferous tubules
11. What are the female gonads called?
Answer
D. ovaries
12. When do the oogonia undergo mitosis?
Answer
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A. before birth
13. From what structure does the corpus luteum originate?
Answer
B. dominant follicle
14. Where does fertilization of the egg by the sperm typically occur?
Answer
C. uterine tube
15. Why do estrogen levels fall after menopause?
Answer
B. There are no follicles left to produce estrogen.
16. The vulva includes the ________.
Answer
D. mons pubis, labia majora, and Bartholin’s glands
17. What controls whether an embryo will develop testes or ovaries?
Answer
C. Y chromosome
18. Without SRY expression, an embryo will develop ________.
Answer
B. female reproductive structures
19. The timing of puberty can be influenced by which of the following?
Answer
D. all of the above (genes, stress, amount of body fat)
Critical Thinking Questions
20. Briefly explain why mature gametes carry only one set of chromosomes.
Answer
A single gamete must combine with a gamete from an individual of the opposite sex to produce a
fertilized egg, which has a complete set of chromosomes and is the first cell of a new individual.
21. What special features are evident in sperm cells but not in somatic cells, and how do these specializations function?
Answer
Unlike somatic cells, sperm are haploid. They also have very little cytoplasm. They have a head with a compact nucleus covered by an acrosome filled with enzymes, and a mid-piece filled with
mitochondria that power their movement. They are motile because of their tail, a structure containing a flagellum, which is specialized for movement.
22. What do each of the three male accessory glands contribute to the semen?
Answer
The three accessory glands make the following contributions to semen: the seminal vesicle contributes about 60 percent of the semen volume, with fluid that contains large amounts of fructose to power the movement of sperm; the prostate gland contributes substances critical to sperm maturation; and the bulbourethral glands contribute a thick fluid that lubricates the ends of
the urethra and the vagina and helps to clean urine residues from the urethra.
23. Describe how penile erection occurs.
Answer
During sexual arousal, nitric oxide (NO) is released from nerve endings near blood vessels within the corpora cavernosa and corpus spongiosum. The release of NO activates a signaling
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pathway that results in relaxation of the smooth muscles that surround the penile arteries, causing
them to dilate. This dilation increases the amount of blood that can enter the penis, and induces the endothelial cells in the penile arterial walls to secrete NO, perpetuating the vasodilation. The rapid increase in blood volume fills the erectile chambers, and the increased pressure of the filled
chambers compresses the thin-walled penile venules, preventing venous drainage of the penis. An erection is the result of this increased blood flow to the penis and reduced blood return from the penis.
24. While anabolic steroids (synthetic testosterone) bulk up muscles, they can also affect testosterone production in the testis. Using what you know about negative feedback, describe what would happen to testosterone production in the testis if a male takes large amounts of synthetic testosterone
Answer
Testosterone production by the body would be reduced if a male were taking anabolic steroids. This is because the hypothalamus responds to rising testosterone levels by reducing its secretion of GnRH, which would in turn reduce the anterior pituitary’s release of LH, finally reducing the manufacture of testosterone in the testes.
25. Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg.
Answer
The sperm must swim upward in the vagina, through the cervix, and then through the body of the
uterus to one or the other of the two uterine tubes. Fertilization generally occurs in the uterine tube.
26. Identify some differences between meiosis in men and women.
Answer
Meiosis in the man results in four viable haploid sperm, whereas meiosis in the woman results in a secondary oocyte and, upon completion following fertilization by a sperm, one viable haploid ovum with abundant cytoplasm and up to three polar bodies with little cytoplasm that are destined to die.
27. Explain the hormonal regulation of the phases of the menstrual cycle.
Answer
As a result of the degradation of the corpus luteum, a decline in progesterone concentrations triggers the shedding of the endometrial lining, marking the menses phase of the menstrual cycle.
Low progesterone levels also reduce the negative feedback that had been occurring at the hypothalamus and pituitary, and result in the release of GnRH and, subsequently, FSH and LH. FSH stimulates tertiary follicles to grow and granulosa and theca cells begin to produce increased amounts of estrogen. High estrogen concentrations stimulate the endometrial lining to rebuild, marking the proliferative phase of the menstrual cycle. The high estrogen concentrations
will eventually lead to a decrease in FSH because of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback that occurs with elevated estrogen production from the dominant follicle stimulates the LH surge that will trigger ovulation. The luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum. Progesterone from the corpus luteum causes the endometrium to prepare for implantation, in part by secreting nutrient-rich fluid. This marks the secretory phase of the menstrual cycle. Finally, in a non-fertile cycle, the corpus luteum will degrade and menses will occur.
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28. Endometriosis is a disease characterized by the presence of endometrial-like tissue found outside the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity. Offer a hypothesis as to why endometriosis increases a woman’s risk of infertility.
Answer
Endometrial tissue proliferating outside of the endometrium—for example, in the uterine tubes, on the ovaries, or within the pelvic cavity—could block the passage of sperm, ovulated oocytes, or a zygote, thus reducing fertility.
29. Identify the changes in sensitivity that occur in the hypothalamus, pituitary, and gonads as a boy or girl approaches puberty. Explain how these changes lead to the increases of sex steroid hormone secretions that drive many pubertal changes.
Answer
As an individual approaches puberty, two changes in sensitivity occur. The first is a decrease of sensitivity in the hypothalamus and pituitary to negative feedback, meaning that it takes increasingly larger concentrations of sex steroid hormones to stop the production of LH and FSH. The second change in sensitivity is an increase in the sensitivity of the gonads to the FSH and LH signals, meaning that the gonads of adults are more responsive to gonadotropins than are
the gonads of children. As a result of these two changes, the levels of LH and FSH slowly increase and lead to the enlargement and maturation of the gonads, which in turn leads to secretion of higher levels of sex hormones and the initiation of spermatogenesis and folliculogenesis.
30. Explain how the internal female and male reproductive structures develop from two different duct systems.
Answer
The internal reproductive structures form from one of two rudimentary duct systems in the embryo. Testosterone secretion stimulates growth of the male tract, the Wolffian duct. Secretions
of sustentacular cells trigger a degradation of the female tract, the Müllerian duct. Without these stimuli, the Müllerian duct will develop and the Wolffian duct will degrade, resulting in a female
embryo.
31. Explain what would occur during fetal development to an XY individual with a mutation causing a nonfunctional SRY gene.
Answer
If the SRY gene were not functional, the XY individual would be genetically a male, but would develop female reproductive structures.
Anatomy & Physiology
Unit 6: Human Development and the Continuity of Life
Chapter 28: Development and Inheritance
Interactive Link Questions
1. View this time-lapse movie (http://openstaxcollege.org/l/conceptus) of a conceptus starting at day 3. What is the first structure you see? At what point in the movie does the blastocoel first appear? What event occurs at the end of the movie?
Answer
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The first structure shown is the morula. The blastocoel appears at approximately 20 seconds. The
movie ends with the hatching of the conceptus.
2. Use this interactive tool (http://openstaxcollege.org/l/embryogenesis) to view the process of embryogenesis from the perspective of the conceptus (left panel), as well as fetal development viewed from a maternal cross-section (right panel). Can you identify when neurulation occurs in the embryo?
Answer
Neurulation starts in week 4.
3. Visit this site (http://openstaxcollege.org/l/pregstages) for a summary of the stages of pregnancy, as experienced by the mother, and view the stages of development of the fetus throughout gestation. At what point in fetal development can a regular heartbeat be detected?
Answer
A regular heartbeat can be detected at approximately 8 weeks.
Review Questions
4. Sperm and ova are similar in terms of ________.
Answer
C. chromosome number
5. Although the male ejaculate contains hundreds of millions of sperm, ________.
Answer
A. most do not reach the oocyte
6. As sperm first reach the oocyte, they will contact the ________.
Answer
B. corona radiata
7. Fusion of pronuclei occurs during ________.
Answer
C. fertilization
8. Sperm must first complete ________ to enable the fertilization of an oocyte.
Answer
A. capacitation
9. Cleavage produces daughter cells called ________.
Answer
D. blastomeres
10. The conceptus, upon reaching the uterus, first ________.
Answer
B. divides
11. The inner cell mass of the blastocyst is destined to become the ________.
Answer
A. embryo
12. Which primary germ layer gave rise to the cells that eventually became the central nervous system?
Answer
B. ectoderm
13. What would happen if the trophoblast did not secrete hCG upon implantation of the blastocyst?
Answer
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C. Menses would flush the blastocyst out of the uterus.
14. During what process does the amnion envelop the embryo?
Answer
A. embryonic folding
15. The placenta is formed from ________.
Answer
C. the mother’s endometrium and the embryo’s chorionic membrane
16. The foramen ovale causes the fetal circulatory system to bypass the ________.
Answer
B. lungs
17. What happens to the urine excreted by the fetus when the kidneys begin to function?
Answer
C. It adds to the amniotic fluid.
18. During weeks 9–12 of fetal development, ________.
Answer
A. bone marrow begins to assume erythrocyte production
19. Progesterone secreted by the placenta suppresses ________ to prevent maturation of ovarian follicles.
Answer
C. FSH and LH
20. Which of the following is a possible culprit of “morning sickness”?
Answer
B. decreased intestinal peristalsis
21. How does the decrease in progesterone at the last weeks of pregnancy help to bring on labor?
Answer
D. decreasing the inhibition of uterine contractility
22. Which of these fetal presentations is the easiest for vaginal birth?
Answer
B. vertex occiput anterior
23. Which of these shunts exists between the right and left atria?
Answer
A. foramen ovale
24. Why is brown fat important?
Answer
B. It can be broken down to generate heat for thermoregulation.
25. Constriction of umbilical blood vessels during vaginal birth ________.
Answer
C. elevates carbon dioxide levels in the blood
26. Alveoli are connected to the lactiferous sinuses by ________.
Answer
B. lactiferous ducts
27. How is colostrum most important to a newborn?
Answer
A. It helps boost the newborn’s immune system.
28. Mature breast milk ________.
Answer
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D. has more fat than cow’s milk
29. Marfan syndrome is inherited in an autosomal dominant pattern. Which of the following is true?
Answer
C. Male and female offspring have the same likelihood of inheriting the disease.
30. In addition to codominance, the ABO blood group antigens are also an example of ________.
Answer
C. multiple alleles
31. Zoe has cystic fibrosis. Which of the following is the most likely explanation?
Answer
D. Zoe must have inherited faulty alleles from both parents, both of whom are carriers.
Critical Thinking Questions
32. Darcy and Raul are having difficulty conceiving a child. Darcy ovulates every 28 days, and Raul’s sperm count is normal. If we could observe Raul’s sperm about an hour after ejaculation, however, we’d see that they appear to be moving only sluggishly. When Raul’s sperm eventually
encounter Darcy’s oocyte, they appear to be incapable of generating an adequate acrosomal reaction. Which process has probably gone wrong?
Answer
The process of capacitation appears to be incomplete. Capacitation increases sperm motility and makes the sperm membrane more fragile. This enables it to release its digestive enzymes during the acrosomal reaction. When capacitation is inadequate, sperm cannot reach the oocyte membrane.
33. Sherrise is a sexually active college student. On Saturday night, she has unprotected sex with her boyfriend. On Tuesday morning, she experiences the twinge of midcycle pain that she typically feels when she is ovulating. This makes Sherrise extremely anxious that she might soon
learn she is pregnant. Is Sherrise’s concern valid? Why or why not?
Answer
Sherrise’s concern is valid. Sperm may be viable for up to 4 days; therefore, it is entirely possible that capacitated sperm are still residing in her uterine tubes and could fertilize the oocyte she has just ovulated.
34. Approximately 3 weeks after her last menstrual period, a sexually active woman experiences a brief episode of abdominopelvic cramping and minor bleeding. What might be the explanation?
Answer
The timing of this discomfort and bleeding suggests that it is probably caused by implantation of the blastocyst into the uterine wall.
35. The Food and Nutrition Board of the Institute of Medicine recommends that all women who might become pregnant consume at least 400 µg/day of folate from supplements or fortified foods. Why?
Answer
Folate, one of the B vitamins, is important for the healthy formation of the embryonic neural tube, which occurs in the first few weeks following conception—often before a woman even realizes she is pregnant. A folate-deficient environment increases the risk of a neural tube defect,
such as spina bidifa, in the newborn.
36. What is the physiological benefit of incorporating shunts into the fetal circulatory system?
Answer
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Circulatory shunts bypass the fetal lungs and liver, bestowing them with just enough oxygenated blood to fulfill their metabolic requirements. Because these organs are only semifunctional in the
fetus, it is more efficient to bypass them and divert oxygen and nutrients to the organs that need it more.
37. Why would a premature infant require supplemental oxygen?
Answer
Premature lungs may not have adequate surfactant, a molecule that reduces surface tension in the
lungs and assists proper lung expansion after birth. If the lungs do not expand properly, the newborn will develop hypoxia and require supplemental oxygen or other respiratory support.
38. Devin is 35 weeks pregnant with her first child when she arrives at the birthing unit reporting
that she believes she is in labor. She states that she has been experiencing diffuse, mild contractions for the past few hours. Examination reveals, however, that the plug of mucus blocking her cervix is intact and her cervix has not yet begun to dilate. She is advised to return home. Why?
Answer
Devin is very likely experiencing Braxton Hicks contractions, also known as false labor. These are mild contractions that do not promote cervical dilation and are not associated with impending
birth. They will probably dissipate with rest.
39. Janine is 41 weeks pregnant with her first child when she arrives at the birthing unit reporting
that she believes she has been in labor “for days” but that “it’s just not going anywhere.” During the clinical exam, she experiences a few mild contractions, each lasting about 15–20 seconds; however, her cervix is found to be only 2 cm dilated, and the amniotic sac is intact. Janine is admitted to the birthing unit and an IV infusion of pitocin is started. Why?
Answer
Janine is 41 weeks pregnant, and the mild contractions she has been experiencing “for days” have dilated her cervix to 2 cm. These facts suggest that she is in labor, but that the labor is not progressing appropriately. Pitocin is a pharmaceutical preparation of synthetic prostaglandins and oxytocin, which will increase the frequency and strength of her contractions and help her labor to progress to birth.
40. Describe how the newborn’s first breath alters the circulatory pattern.
Answer
The first breath inflates the lungs, which drops blood pressure throughout the pulmonary system, as well as in the right atrium and ventricle. In response to this pressure change, the flow of blood temporarily reverses direction through the foramen ovale, moving from the left to the right atrium, and blocking the shunt with two flaps of tissue. The increased oxygen concentration also constricts the ductus arteriosus, ensuring that these shunts no longer prevent blood from reaching
the lungs to be oxygenated.
41. Newborns are at much higher risk for dehydration than adults. Why?
Answer
The newborn’s kidneys are immature and inefficient at concentrating urine. Therefore, newborns
produce very dilute urine—in a sense, wasting fluid. This increases their risk for dehydration, and makes it critical that caregivers provide newborns with enough fluid, especially during bouts
of vomiting or diarrhea.
42. Describe the transit of breast milk from lactocytes to nipple pores.
Answer
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Milk is secreted by lactocytes into alveoli. Suckling stimulates the contraction of myoepithelial cells that squeeze milk into lactiferous ducts. It then collects in lactiferous sinuses and is secreted
through the nipple pores.
43. A woman who stopped breastfeeding suddenly is experiencing breast engorgement and leakage, just like she did in the first few weeks of breastfeeding. Why?
Answer
It takes time to establish a balance between milk supply and milk demand. When breastfeeding stops abruptly, it takes time for the supply to fall. Excessive milk supply creates breast engorgement and leakage.
44. Explain why it was essential that Mendel perform his crosses using a large sample size?
Answer
By using large sample sizes, Mendel minimized the effect of random variability resulting from chance. This allowed him to identify true ratios corresponding to dominant–recessive inheritance.
45. How can a female carrier of an X-linked recessive disorder have a daughter who is affected?
Answer
The only way an affected daughter could be born is if the female carrier mated with a male who was affected. In this case, 50 percent of the daughters would be affected. Alternatively, but exceedingly unlikely, the daughter could become affected by a spontaneous mutation.
This file is copyright 2016, Rice University. All Rights Reserved.
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