2014-Exam 4 09am for Posting w Answers

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1 BISC 220L – Old Exam 4 (from 2014) 9 am Version 1. Which one of the following occurs when a person is dehydrated? (d) a. a decrease in plasma osmolarity b. decreased secretion of vasopressin c. an increase in blood flow through the kidney d. a shift of water from the intracellular fluid to the extracellular fluid -ANS 2. Diabetes insipidus is a condition caused by either an insufficient secretion of antidiuretic hormone (ADH) or insensitivity of the kidney to ADH. Which one of the following symptoms would not be expected in a patient with diabetes insipidus? (d) a. Tendency toward dehydration of body fluids b. Frequent awakening at night to urinate c. Pale urine with low osmolarity d. Diminished thirst -ANS 3. Which one of the following is not an effect of atrial natriuretic hormone? (e) a. inhibition of renin release from the juxtaglomerular apparatus b. inhibiting the effects of antidiuretic hormone c. increasing the volume of urine production d. inhibition of aldosterone release e. increasing blood pressure -ANS 4 . One advantage of urea excretion over uric acid excretion is that urea… (e) a. is not toxic. b. is a larger molecule. c. requires no water to excrete. d. can be concentrated to a greater extent. e. requires less energy to synthesize than uric acid. -ANS 5. Central diabetes insipidus is a clinical condition that results in the production of large volumes of dilute urine. Which one of the following is consistent with this condition? (d) a. excessive secretion of renin b. excessive secretion of antidiuretic hormone c. excessive secretion of aldosterone d. damage to the posterior pituitary -ANS e. high levels of angiotensin II in the plasma 6. If a child were born with a mutation that made the ascending limb of the loop of Henle permeable to water, what would be the minimum and maximum urine osmolarities the child could produce? Units are in mOsM. (d) a. minimum 100 / maximum 300 d. minimum 300 / maximum 300 -ANS b. minimum 300 / maximum 1200 e. minimum 100 / maximum 1200 c. minimum 100 / maximum 100 7. Which one of the following would most likely increase the rate at which fluid is filtered into kidney tubules? (c)

2 a. higher than normal plasma protein concentration b. constriction of the efferent arteriole c. dilation of the afferent arteriole -ANS d. kidney stones in the renal pelvis 8. Which one of the following is not an appropriate response to acidification of body fluids (acidosis)? (b) a. increased respiration c. increased HCO 3 - reabsorption in the kidneys b. decreased H + secretion in distal tubules – ANS d. None of the other answers is correct. 9. Which one of the following statements about atrial natriuretic hormone (ANH) is false ? (c) a. ANH inhibits release of aldosterone. b. ANH inhibits release of antidiuretic hormone. c. ANH stimulates constriction of systemic arterioles. -ANS d. ANH inhibits release of renin from the juxtaglomerular apparatus. e. ANH inhibits reabsorption of Na + in the distal tubule and upper collecting duct. 10. In a healthy individual, the glomerular filtration rate is 100 ml/min, the concentration of glucose in the plasma is 2 mg/ml, and pressure in the glomerular capillaries is 50 mm Hg. At what rate do the kidneys reabsorb glucose? (d) a. 50 mg/min d. 200 mg/min -ANS b. 100 mg/min e. Insufficient information is given to answer. c. 150 mg/min 11. Imagine that you applied a drug that specifically inhibits Na + /K + pumps in epithelial cells in the upper half of the ascending limb of the loop of Henle. If no other compensatory changes occurred, what effect would this drug have on the volume of urine produced? (b) a. The volume of urine produced would decrease. b. The volume of urine produced would increase. -ANS c. The drug would have no effect on the volume of urine produced. d. The effect on volume of urine produced cannot be determined from the information given. 12. Which one of the following is not likely to cause a rise in blood pressure? (d) a. renin b. aldosterone c. antidiuretic hormone d. atrial natriuretic hormone -ANS 13. Which one of the following statements is false ? (d) a. Atrial natriuretic hormone reduces water reabsorption in the kidney. b. Angiotensin II raises blood pressure by causing vasoconstriction in arterioles. c. Reabsorption of H 2 O can occur everywhere in the nephron except in the ascending limb of the loop of Henle. d. By blocking the action of antidiuretic hormone, alcohol causes excess reabsorption of H 2 O in the kidney. -ANS 14. Both epinephrine and cortisol are secreted in response to stress. Which one of the following statements is true for both of these hormones? (e)

3 a. Both hormones are secreted into the blood within seconds of the onset of stress. b. Receptors for both hormones are on the surfaces of target cells. c. Adrenocorticotropin stimulates the release of both hormones. d. Both hormones are secreted by the adrenal cortex. e. Both hormones increase levels of blood glucose. -ANS 15. A woman complained to a doctor that she has no energy, has been putting on weight, and is cold all the time. The doctor finds that her pulse rate is low and that she has low blood pressure. Laboratory tests reveal that plasma levels of thyroid hormone are low but that levels of thyroid stimulating hormone (TSH) are high. Which one of the following statements is false ? (b) a. The patient’s general level of metabolism is low. b. High levels of TSH rule out a hypothyroid condition. -ANS c. An appropriate treatment would be to administer thyroid hormone. d. Similar conditions in an infant would likely cause mental retardation. 16. Which one of the following hormones is incorrectly paired with its function? (d) a. glucagon – stimulates glycogenolysis b. cortisol – stimulates gluconeogenesis c. insulin – stimulates glucose uptake in most cells d. somatostatin – stimulates release of growth hormone -ANS e. melanocyte stimulating hormone – suppresses appetite 17. In which one of the following ways are testosterone and thyroid hormone similar? (d) a. Both hormones bind to G protein-coupled receptors. b. Both hormones are released from secreting cells by exocytosis. c. The immediate effect of both hormones is a rise in intracellular cAMP. d. Receptors for both hormones are located in the cytoplasm or nucleus. -ANS e. Both hormones stimulate catabolism, or breakdown, of cellular proteins. 18 . Hypercalcemia would likely result in increased… (e) a. reabsorption of Ca 2+ in the kidneys. d. excitability of neurons. b. secretion of parathyroid hormone. e. secretion of calcitonin. -ANS c. release of Ca 2+ from bones. 19. Which one of the following hormones originates in the anterior pituitary? (d) a. calcitonin d. thyroid stimulating hormone -ANS b. epinephrine e. growth hormone releasing hormone c. testosterone 20. Which one of the following statements is not correct ? (e) a. The action of cortisol is necessary for glucagon to be fully effective. b. Administration of a glucocorticoid drug should cause a decrease in ACTH secretion. c. In Grave’s disease, one would expect that circulating levels of T 4 would be high and levels of TSH would be low. d. In Hashimoto’s disease, one would expect that circulating levels of T4 would be low and levels of TSH would be high.

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4 e. In a patient with a hormone-secreting tumor of the corticotropes of the anterior pituitary, levels of CRH secretion should be high. -ANS 21. Which one of the following correctly describes a function of gap junctions between adjacent cells? (d) a. They allow G-proteins to diffuse between cells. b. They allow activated kinases to diffuse between cells. c. They cause adjacent cells to adhere strongly to each other. d. They allow second messenger molecules to diffuse between cells. -ANS e. They form a diffusion barrier, so extracellular solutes cannot leak between cells. 22. A 35-year old woman who routinely uses iodized salt shows up at a doctor’s office with a painless enlargement in her neck. She complains of always feeling cold and lethargic. Which one of the following laboratory test results would you most likely find in this patient? (b) a. Low levels of TRH secretion. b. High levels of TSH secretion. -ANS c. Antibodies that stimulate TSH receptors. d. Low levels of growth hormone secretion. e. High levels of thyroid hormone secretion. 23. When exposed to a particular hormone, there is a marked increase in the activity of G-proteins in the membrane of the target cell. The hormone is most likely… (b) a. a steroid. d. estrogen b. a peptide. -ANS e. aldosterone c. a thyroid hormone 24 . Immediately after a meal, when nutrients are being absorbed from the digestive tract, … ( e) a. glucagon is released. b. release of insulin is inhibited. c. body cells take up less glucose. d. protein synthesis in the liver decreases. e. glycogen synthesis in the liver increases. – ANS 25 . Calcium homeostasis primarily reflects… (e) a. regulation of the Ca content of bones. b. regulation of blood Ca levels by the kidneys. c. a balance between the effects of parathyroid hormone and aldosterone. d. a balance between Ca absorption from the intestine and Ca excretion by the kidneys. e. interplay between Ca reserves in bone, absorption from the intestine, and excretion by the kidneys. -ANS 26. A distinctive feature of the mechanism of action of steroid hormones and thyroid hormones is that … (b) a. these hormones affect metabolism. b. these hormones bind to intracellular receptors. -ANS c. the secretion of these hormones is regulated by feedback loops. d. target cells react more rapidly to these hormones than to most other hormones. e. these hormones bind to specific receptor proteins on the plasma membranes of target cells. 27. Where in the reproductive tract of women does fertilization usually take place? (d)

5 a. vagina d. oviduct -ANS b. cervix e. ovary c. uterus 28. Which one of the following statements is false ? (d) a. In the reproductive cycle of women, levels of LH are highest just before ovulation. b. Semen is composed of sperm plus the secretions of the prostate gland, seminal vesicles, and bulbourethral glands. c. In the ovary, theca cells secrete estrogen. -ANS d. In women, estrogen inhibits FSH secretion directly and LH secretion indirectly. 29. Which one of the following statements is false ? (a) a. The follicular phase of the ovarian cycle occurs in between the ovulatory phase and the menstrual phase. -ANS b. Semen contains sperm plus the secretions of the seminal vesicles, prostate gland, and bulbourethral gland. c. The corpus luteum remains active during early pregnancy because of chorionic gonadotropin secreted by the developing embryo. d. Continual administration of testosterone will lead to a decrease in FSH and LH secretion. 30. Which one of the following statements about the endocrine control of reproduction is true ? (b) a. Testosterone directly inhibits FSH secretion. b. FSH receptors are located on Sertoli cells. -ANS c. LH receptors are located on Sertoli cells. d. Inhibin directly inhibits LH secretion. e. Sertoli cells secrete testosterone. 31. Which one of the following functions of Sertoli cells mediates negative feedback control of FSH secretion? (c) a. secretion of LH b. spermatogenesis c. secretion of inhibin -ANS d. secretion of testosterone e. conversion of testosterone to estrogen 32. A 46-year old male patient with multiple autoimmune diseases developed an autoantibody against the FSH receptor that blocked FSH activity. Which one of the following statements is most likely to be false ? (d) a. The sperm count will be lower than normal. b. Plasma levels of FSH will be higher than normal. c. Plasma levels of LH should be in the normal range. d. Plasma levels of inhibin will be higher than normal. -ANS e. Plasma levels of GnRH should be in the normal range. 33. During the follicular phas e of the ovarian cycle, FSH stimulates increasing secretion of estrogen from… (c) a. theca cells d. primary oocytes b. corpora lutea e. secondary oocytes c. granulosa cells -ANS

6 34. Which one of the following incorrectly pairs a hormone with its action? (c) a. GnRH o controls release of FSH and LH b. Luteinizing hormone o stimulates ovulation c. Progesterone o stimulates development of ovarian follicles -ANS d. Chorionic gonadotropin o maintains secretions from corpus luteum e. Estrogen o inhibits secretion of prostaglandins in the endometrium of the uterus 35 . During most of the first half of the ovarian cycle, the ovary is… (a) a. maturing a follicle. – ANS b. secreting progesterone. c. forming a corpus luteum. d. secreting declining amounts of estrogen. e. secreting both estrogen and progesterone. 36. In the membrane of a typical resting neuron in the brain, K + permeability is 20 times higher than Na + permeability. Most of the neurons that synapse onto this neuron release the neurotransmitter GABA. Binding of GABA to its receptor opens a GABA-gated K + channel. Which of the following is most likely to happen to the neuron when these GABA synapses are activated? (b) a. depolarization d. depolarization followed by hyperpolarization b. hyperpolarization -ANS e. hyperpolarization followed by depolarization c. no change in membrane potential 37. Some neurons are treated with a drug that blocks Cl - ion channels, and in response, the cells depolarize slightly. Which one of the following is a correct conclusion about the normal state of these cells, before the drug was applied? (c) a. The cells do not actively transport Cl - ions. b. Cl - ions are actively transported into the cells. c. Cl - ions are actively transported out of the cells. -ANS d. Insufficient information is given to determine if and how Cl - ions are transported. 38. Which one of the following statements about gap junctions or electrical synapses is false ? (b) a. Electrical synapses can only be excitatory, never inhibitory. b. Gap junction channels are too small to allow glucose molecules to pass through. -ANS c. Adjacent muscle cells in the heart are electrically coupled by gap junctions. d. Electrical synapses are often found in neural circuits where it is important for synaptic transmission to be rapid. 39. Which one of the following statements is false ? (d) a. As an action potential propagates along a typical myelinated axon, the amount of Na + current entering each node of Ranvier is usually sufficient to depolarize the next 2-3 nodes to threshold. b. If an isolated axon is given a stimulus just above threshold, and then a stimulus twice as large, action potentials will travel at the same velocity in both cases. c. Z -conotoxin, a drug which blocks voltage-gated Ca 2+ channels, will have no effect on action potential propagation in a typical axon. d. Z -conotoxin, a drug which blocks voltage-gated Ca 2+ channels, will likely increase the amount of neurotransmitter released when an action potential propagates into a presynaptic terminal. -ANS

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7 40. Which one of the following statements is false ? (d) a. In the cytoplasm of a typical neuron, [K + ] is higher than in the surrounding extracellular fluid. b. If the membrane of a neuron were only permeable to Na + ions, then the resting membrane potential would have a positive value. c. Na/K pumps in glial cells remove K + ions from the extracellular space surrounding active neurons. d. In the membrane of myelinated axons, voltage-gated Na + channels are restricted to the internodal regions. -ANS 41. Which one of the following statements is false ? (b) a. Myelination increases the conduction velocity of action potentials in axons. b. In a mammal, raising extracellular Na+ concentration by 20 mM is likely to depolarize the resting membrane potential of a typical neuron. -ANS c. The Na/K ATPase removes Na+ ions from the inside of the neuron. d. In an experiment, lowering the [Ca2+] of the bathing solution is likely to reduce the amount of neurotransmitter released when an action potential propagates into a presynaptic terminal. 42. Tetrodotoxin, a neurotoxin found in the tissues of puffer fish (known as fugu to the Japanese), binds specifically to voltage-gated Na + channels and prevents the channels from opening. A few bites of poorly prepared fugu would cause … (e) a. increased transmitter release at most chemical synapses b. prolongation of action potential duration. c. hyperpolarization of nerve cells. d. depolarization of nerve cells. e. respiratory arrest. -ANS 43. The diagram shows a segment of an unmyelinated axon through which an action potential is propagating in the direction shown. A single instant in time is depicted. At this instant, shaded region #2 is where voltage-gated Na + channels are open. Which one of the following statements is false ? (d) a. In region #1, K + ions are flowing out of the cell through voltage-gated K + -channels. b. Current flowing through the extracellular fluid between region #3 and region #2 is carried mostly by Na + and Cl - ions. c. Current entering the axon in region #2 leaves the axon in regions #1 and #3. d. The flow of Na + ions entering the axon in region #2 is equal and opposite to the flow of K + ions leaving the axon in region #2. -ANS 44. If you increased the internal concentration of K + in a typical neuron, what immediate effect would this have on the resting membrane potential (V m )? (c) a. V m would depolarize. b. V m would not change. c. V m would hyperpolarize. -ANS d. V m would approach 0 mV. direction of propagation 1 2 3

8 45. Which one of the following statements about the action potential is false ? (c) a. At rest, there are more K channels open than there are Na channels open. b. Na channel activation gates open before Na channel inactivation gates close. c. During the undershoot or after-hyperpolarization, fewer K channels are open than at resting conditions. -ANS d. Closing of Na channel inactivation gates and opening of K channel activation gates is responsible for the repolarization phase of the action potential. 46. Which one of the following is most responsible for restoration of the resting potential after the peak of an action potential in a typical nerve cell? (e) a. increased activity of the Na + /K + pump. b. opening of voltage-gated Cl - channels. c. opening of Na + channel activation gates. d. opening of both voltage-gated K + channels and voltage-gated Cl - channels. e. opening of voltage-gated K + channels and closing of Na + channel inactivation gates. -ANS 47. Which one of the following statements is false ? (b) a. In a typical neuron, both the chemical and electrical gradients tend to drive Ca ++ ions into the cell. b. In a typical neuron, proteins necessary for transmitter release are synthesized in the presynaptic terminals. -ANS c. In a typical neuron, the chemical gradient tends to drive K + ions out of the cell and the electrical gradient tends to drive K + ions into the cell. d. Assuming that a neuron has the typical distribution of Na + ions across its plasma membrane, and that the membrane is permeable only to Na + ions, the inside of the cell would be positive with respect to the outside. 48 . In most neurons, the concentration of… (c) a. both Na + and K + ions is higher inside the cell than outside. b. both Na + and K + ions is higher outside the cell than inside. c. Na + ions is higher outside the cell and K + ions is higher inside the cell. -ANS d. Na + ions is higher inside the cell and K + ions is higher outside the cell. 49. Which one of the following statements is false ? (d) a. In presynaptic terminals of chemical synapses, Ca 2+ ions trigger exocytosis of transmitter-filled vesicles. b. A single type of neurotransmitter can have multiple postsynaptic actions depending on the type of receptor to which it binds. c. Temporal summation occurs when a single synaptic input is activated twice in succession, with the second PSP occurring before the first PSP is over. d. If a neurotransmitter opens a Cl - channel when it binds to its postsynaptic receptor, and this causes influx of Cl - ions, the synapse would be excitatory. -ANS e. In the optic tectum of the hunting rattlesnake, spatial summation is used to combine inputs from visual and thermoreceptive layers in order to make a decision whether to strike at a mouse-like object. 50. Cardiac muscle fibers contract rhythmically because they spontaneously generate action potentials at a fairly constant rate. Axons in the vagus nerve release acetylcholine onto the heart. When ACh binds to

9 muscarinic ACh receptors on the muscle cells, changes in intracellular second messengers cause an increase in K + permeability in the heart cell membrane. Which one of the following statements is false? (b) a. Vagus nerve activity slows the rate of heart beating. b. Vagus nerve activity is likely to depolarize heart muscle cells. -ANS c. Vagus nerve will prolong the duration of the action potential in the heart muscle cell. d. When the vagus nerve is active, there is likely to be an increase in outward K+ current across the muscle cell membrane. 51. Which one of the following best describes the role of Ca 2+ ions in the contraction of vertebrate skeletal muscles? (c) a. Ca 2+ breaks cross-bridges by acting as a cofactor in the hydrolysis of ATP. b. Ca 2+ influx through voltage-gated Ca 2+ channels spreads excitation along the fiber membrane. c. Ca 2+ ions trigger a change in the conformation of tropomysosin, so that myosin-binding sites on actin are exposed. -ANS d. Ca 2+ influx through voltage-gated Ca channels generates action potentials that spread along the muscle fiber membrane. 52. Dantrolene is a drug that lowers the concentration of free Ca 2+ ions within muscle fibers, perhaps by blocking release of Ca 2+ from the sarcoplasmic reticulum. What effect would you expect dantrolene to have on muscle function? (a) a. It would reduce the strength of muscle contraction. -ANS b. It would prolong the duration of the muscle twitch. c. It would increase the likelihood of developing muscle cramps. d. It would exaggerate muscle reflexes such as the stretch (knee-jerk) reflex. 53. If one type of skeletal muscle fiber has twice the number of Ca 2+ pumps (Ca 2+ ATPases) in its sarcoplasmic reticulum compared to another type of fiber, but otherwise the fibers are the same, how would the twitch contractions of the two fiber types differ? (b) a. The fibers with more Ca 2+ pumps would twitch more strongly. b. The fibers with more Ca 2+ pumps would exhibit a twitch with shorter duration. -ANS c. Twitches in the fibers with more Ca 2+ pumps would be more resistant to fatigue during prolonged activity. d. Twitches in the fibers with more Ca 2+ pumps would likely be graded, rather than all-or-none, in amplitude.

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2014-Exam 4 09am for Posting w Answers

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