FINAL REVIEW_ LEARNING OBJECTIVES

WEEK 1 LEARNING OBJECTIVES Discuss how a signal can lead to both short- and long-term responses. Signaling cell → Signaling molecule → Receptor protein → Response (1) Signal binds and the receptor is activated. (conformational change) (2) Signal transduction occurs where one molecule activates the next (3) Response: enzyme activity, turning on of genes, signals other cells, or causes transcription of the proteins. G-protein coupled signaling is short term. Ex. activating enzymes or opening ion channels Receptor kinase signaling is long term. Ex. activating growth and development, changes in gene expression, or differentiation cells. Short-term response: - Paracrine signaling - Autocrine signaling - Cell-to-cell contact Long-term response: - Endocrine signaling Describe the mechanism of action for a receptor tyrosine kinase pathway. (1) Inactive Receptor The signal molecules bind to the extracellular portion of the receptor. (2) Dimerization Causes a conformational change in the cytoplasmic domain which activates the tyrosine kinase catalytic activity. ATP is also converted to ADP in this process. (3) Active Receptor The conversion of ATP to ADP allows each member of the receptor pair to attach phosphate groups to one another. Essentially, phosphorylation occurs. (4) These phosphate groups provide binding sites for intracellular signaling proteins, which activates them. Define the role of kinases and phosphatases in cell signaling pathways. Kinases- enzymes that catalyze the transfer of a phosphate group from ATP to a substrate (phosphorylation), which activates the protein. Phosphatases— remove a phosphate group (dephosphorylation), and protein becomes inactive. Distinguish the potential for differentiation of totipotent, pluripotent, and multipotent stem cells. Totipotent— can give rise to a complete organism (most potential) Pluripotent— can become any of the three germ layers (ectoderm, mesoderm, endoderm). (Less potential) Multipotent— can form a limited number of specialized cells (least potential)

Evaluate why diffusion and surface area limit cell size and its implications for large, multicellular organisms. As volume increases, surface area decreases. Bigger cells require more nutrients. However, as they get bigger they cannot hold much of the nutrients and their ability to discard waste is reduced. Waste removal is faster in small cells. Implication: large, multicellular organisms have lots of little cells. The smaller the surface area to volume ratio, the slower the rate of diffusion across the surface. Determine if certain proteins in a signaling pathway function as phosphatases, kinases, or neither. If it adds a phosphate group and activates protein, then it is a kinase. If it removes phosphate and deactivates the protein, then it is a phosphatase. If it does neither, then it is neither. Explain how a signal transduction pathway can be turned off. (1) Binding affinity: the length of time a signaling molecule remains bound to its receptor depends on how tightly the receptor holds on to it. The ligand is released from the receptor. (2) G proteins can catalyze the hydrolysis of GTP to GDP and inorganic phosphate. This means that an active, GTP-bound α subunit in the "on" position automatically turns itself "off" by converting GTP to GDP. In fact, the α subunit converts GTP to GDP almost as soon as a molecule of GTP binds to it. Without an active receptor to generate more active G protein α subunits, transmission of the signal quickly comes to a halt. (3) Phosphatases remove phosphate groups deactivating proteins. (4) Enzymes degrade cAMP, converting the second messenger cAMP to AMP which no longer activates protein kinase A. Predict the effect of altering part of a signal transduction pathway. When one part of the signal transduction pathway is altered, it affects everything else downstream. Interpret data related to different types of cell signaling pathways. cell signal (ligand) → receptor activation → signal transduction → response → termination Paracrine signaling: short distance (diffusion) Synaptic signaling: short distance (ligands are neurotransmitters) Autocrine signaling: cell signals to itself Endocrine: signals release through bloodstream Cell-to-cell contact: stuck together, signal can be a transmembrane protein Predict cell fate based on cell activation of signaling pathways. There could be signals that only activate certain genes that limits what the cells can differentiate to. Describe the different types of cell-cell Cell junctions physically connect one cell to the next and anchor cells to the

division (cytokinesis), movement (crawling), and vesicle transport Intermediate filament:A polymer of proteins, which vary according to cell type, that combine to form strong, cable-like filaments that provide animal cells with mechanical strength. Function: cell shape and support, strength and support to tissues under stress (skin and intestine) Explain how motor proteins actively move material around the cell. Kinesin and dynein are associated with microtubules. Kinesin— transports towards the plus end of microtubule. A motor protein, similar in structure to myosin, that transports cargo toward the plus end of microtubules. Dynein— away from the plasma membrane, towards the minus end. A motor protein that carries cargo away from the plasma membrane toward the minus ends of microtubules. Driven by conformational changes and ATP. Microtubules are found in cilia and flagella. Microfilaments are associated with motor proteins. Actin microfilaments and myosin transport in vesicles. Moving actin filaments inside muscle cells cause muscle contraction. Explain how cell-cell junctions and the extracellular matrix (ECM) contribute to cells' ability to form tissues and organs. Cell-cell junctions: - Junctions allow structure and stability by adherens and desmosomes, allowing cells to form together by cadherins - Tight junctions form shapes as they separate cells from cells and create a barrier. - Gap junctions allow molecules and signals to pass allowing the cell to function. Extracellular matrix: - Holds cells together, filter materials passing through tissues, help orient cell movement, chemical signaling. - Mutations in the function of the extracellular matrix cause fragile tissues. Evaluate how changing components of the cytoskeleton would change cell structure (shape) and/or function (i.e., motility). - In eukaryotes, an internal protein scaffold that helps cells maintain their shape and serves as a network of tracks for the movement of substances within cells. - There are three groups of movers, the motor proteins: kinesin, dynein and myosin, and three main groups of shapers, the protein filaments: microtubules, intermediate filaments and actin filaments. - The protein fibers of the cytoskeleton provide internal support for cells. ** In addition to providing structural support, microtubules and microfilaments enable the movement of substances within cells as well as changes in cell shape. Altered activity of motor proteins can lead to build-up or loss of cellular components.

Evaluate the effect of modifying cell-cell junctions or ECM components on tissue structure and function. If you compromise the ECM then your skin or epithelial tissues will not have strength in presence of pressure/stress → bed sores If adherens or desmosome → no cell to cell adhesion If hemidesmosomes → then cell can't connect to extracellular matrix If tight junction → then there would be no boundary for the skin, intestine, stomach, bladder → and molecules can go right through, there would be no seal WEEK 2 LEARNING OBJECTIVES Describe the general structure of a neuron. Sensory → Interneurons → Motor Sensory neuron - receives info from stimulus and send to interneurons Interneuron - received info from sensory neurons and transmits it to motor neurons Motor Neuron - receive info from interneuron, effects response in body Relate the structural features of a neuron (i.e., dendrites, axons) to their functions. Dendrite - receives stimulus from presynaptic neuron. Receives signals from other nerves, input end of the nerve cell. Cell body: junction where signals pass from dendrite to axon hillock. Axon Hillock - start of action potential. Point where signals are summed if the sum is high enough an action potential gets fired. Axon - action potential travels down axon. Transmits signals away from nerves cell body Myelin sheath - insulate neuron → saltatory propagation. As result, action potentials "jump" from node to node increasing speed of conduction. Nodes of Ranvier - exposed sites (lots of ion channels). Exposed axon membrane sites between myelin sheaths. Concentrated with voltage-gated Na+/K+ channels Axon terminal - release neurotransmitters Explain membrane potential and how it arises in both neuronal and non-neuronal cells. Membrane potential: measurement of charge difference between the inside and the outside of the neuron. Resting membrane potential = -70mV (more positive on the outside) - More Na+ outside and more K+ inside (K+ leaks out) Refers to negative voltage across the membrane at rest, mainly due to K+ leak channels and the negatively charged proteins inside the cell membrane compared to positive outside membrane. Also, due to the sodium potassium

Evaluate how multiple signals will be integrated by a postsynaptic neuron that has formed synapses with two or more presynaptic neurons. Temporal Summation - multiple EPSPs arrive quickly at single synapse Spatial Summation - multiple ESPS arrive at different locations simultaneously → generates an action potential Cancellation - EPSPs and IPSPs cancel each other out Postsynaptic membranes contain multiple receptors, and can bind many different neurotransmitters. → when EPSP and IPSP both arrive on postsynaptic membrane = action potential generated → temporal summation on postsynaptic = action potential Cell sums all the inputs -> if summed input breaches threshold potential, an action potential is fired at axon hillock Temporal Summation = summed over time, frequency of synaptic stimuli determines action potential Spatial Summation = summed over space, number of synaptic stimuli received from different regions of the postsynaptic cell's dendrites determines action potential Predict how a charged molecule will move across a semipermeable membrane in the presence of an electrochemical gradient. Chemical gradients come from concentration differences. Electrical gradients come from charge separation. Electrical gradients are stronger than chemical gradients. Charged molecule will move down its electrochemical gradient (ie. if positive will move to negative side) Predict how addition of drugs or the introduction of mutated proteins will alter membrane potential, excitability, and/or signal transmission Opioids bind to ligand-gated channels on postsynaptic cell → increased ion movement → increased signal → cell destroys receptors to decrease signal → need heavier dose of opioid to increase signal (get the same feeling) +drugs affecting CNS causes decrease in postsynaptic cells and needs higher doses + drugs interrupting membrane potential/encouraging leaks makes neurons unable to fire or overfire Describe the global organization of the human nervous system. Central nervous system-- brain, spinal cord Peripheral nervous system-- sensory and motor nerve PNS split into: Somatic (Voluntary component)-- sensing and responding to external stimuli => split into motor nerves (efferent toward PNS) and sensory (afferent toward CNS) Autonomic (Involuntary component)-- regulate internal bodily functions =>

sympathetic (flight or fight) and parasympathetic (rest and digest) *** Afferent neurons carry information from sensory receptors of the skin and other organs to the central nervous system (i.e., brain and spinal cord), whereas Efferent neurons carry motor information away from the central nervous system to the muscles and glands of the body. Relate the major regions of the brain, including the hypothalamus, thalamus, and sensory cortex to their respective functions. Frontal Lobe- decision making and planning Parietal Lobe- body awareness, ability to do complex tasks (ex. dressing) Temporal Lobe- processing sound Occipital Lobe- processing visual information Primary Motor Cortex- complex, coordinated behaviors by controlling skeletal muscle movements Primary Sensory Cortex- integrates tactile information from specific body regions and relays this information to the motor cortex Cerebellum: balance; coordinates complex motor tasks with sensory and motor info Brainstem: initiates and regulates motor functions such as walking, posture, breathing and swallowing. Connects brain to spine => controls the flow of messages between the brain and the rest of the body Hypothalamus- endocrine function, hormone production, autonomic function Thalamus- relay motor and sensory signals to the cerebral cortex Compare and contrast the sympathetic and parasympathetic divisions of the autonomic nervous system. *** They cannot occur at the same time because they affect the same pathway. Sympathetic “fight or flight” - accelerated heart rate, dilates pupils, stimulates glucose release - arousal and increased activity - nerves leave CNS from middle region of spinal cord Parasympathetic “rest and digest” - constricts pupils, slows heart, increases digestion - nerves leave CNS from brain via cranial nerves Explain how the brain receives, processes, and sends information. (1) Sensory info received by cranial nerves and spinal cord nerves (2) Pass through brainstem → thalamus → specialized region in cerebral cortex Evaluate which region of the brain has been damaged in a patient based on a set Broca's Area - Struggling to produce language but can comprehend speech → frontal lobe

(effector) to contract more forcefully. The uterine contractions, in turn, cause the pituitary gland to produce more oxytocin causing more contractions until the offspring is born. Predict how components of a homeostatic system will change when part of the system is perturbed. Depends on the situation. The process will get disrupted, however. Apply the concept of negative feedback to the process of thermoregulation. Hot: Temperature rises [Stimulus] -> Thermoregulation center in brain activates [Sensor] -> Sweat glands release sweat [Effector] -> Temperature decreases as skin cools from sweat evaporation [Response] Cold: Temperature falls [Stimulus] -> Thermoregulation center in brain activates [Sensor] -> Skeletal muscles rapidly contract, shivering [Effector] -> Temperature rises as shivering generates heat [Response] Relate changes in environmental conditions to changes in physiological or behavioral responses to temperature regulation. Many animals regulate their body temperature through behavior, such as seeking sun or shade or huddling together for warmth. → Endotherms can alter metabolic heat production to maintain body temperature using both shivering and nonshivering thermogenesis. → Vasoconstriction — shrinking and expansion of blood vessels to the skin can alter an organism's exchange of heat with the environment. A countercurrent heat exchanger is an arrangement of blood vessels in which heat flows from warmer to cooler blood, usually reducing heat loss. Some animals use body insulation and evaporative mechanisms, such as sweating and panting, in body temperature regulation. Relate endocrine function to homeostatic regulation. The endocrine system plays an important role in homeostasis because hormones regulate the activity of body cells. → The release of hormones into the blood is controlled by a stimulus. → The hypothalamus' function in the endocrine system is to control and stimulate the pituitary gland. The hypothalamus and pituitary gland are connected via a system of blood vessels. Hormones produced in the hypothalamus travel through the vessels and stimulate the pituitary gland. The hypothalamus produces inhibiting or releasing hormones. → Our thyroid gland is located in the neck and stimulated by TSH, which is appropriately called thyroid stimulating hormone. The thyroid is responsible for metabolism, regulating body temperature, the development of the nervous system, reproductive system and heart function. The thyroid secretes two hormones, T3 and T4, which are collectively called TH (thyroid hormone). → The pancreas is also part of the endocrine system. Insulin and glucagon are

secreted by the pancreas to regulate blood sugar levels. Among the cells used for digestion, are cells that produce hormones. → Alpha (α) cells secrete glucagon, which elevates the level of glucose in the blood. → Beta (β) cells secrete insulin, which decreases the level of glucose. In females, the important hormones are estrogen and progesterone. Both are produced in the ovaries. They regulate the menstrual cycle and initiate production of eggs. Interstitial cells in the testes produce testosterone, which is the important sex hormone in males. Testosterone is responsible for sperm production and developing the secondary sexual traits. Explain when and why hormones are released. Chemical compounds secreted by cells or glands that act on other cells or glands in the body either locally or at distant sites (transported through the bloodstream). They are released in response to a signal promoting growth, homeostasis, reproduction, and regulation. Define the different types of hormones. Peptide/Amine Hormones - Due to their hydrophilic nature, they are unable to cross the cell's hydrophobic plasma membrane. Therefore, they are only able to bind to cell surface receptors. When binding to cell surface receptors, they activate second messenger pathways through the cell, resulting in changes in the metabolic state or gene expression of the target cell. - Peptide Hormones: type of hormone made from a chain of amino acids Example(s): Oxytocin and ADH - Amine Hormones: type of hormone derived from a single aromatic amino acid Example(s): Epinephrine, Norepinephrine, and Dopamine are all derived from the amino acid phenylalanine Steroid Hormones - A type of hormone derived from cholesterol - Due to their hydrophobic nature, they are able to cross the cell's hydrophobic plasma membrane. Inside the cell they bind to nuclear/cytoplasmic receptors, causing them to act as transcription factors which change the gene expression of the target cell. - Affect DNA transcription, more profound and long lasting effects Discuss the role that hormones play in the maintenance of homeostasis. Changes in levels are detected and hormones are released/inhibited in response. Send signals to stop the disturbance accordingly. Provide examples of organisms that rely on different modes of reproduction r -strategies - lots of babies, not much parental care

Spermatogenesis: happens continuously Sperm generated in testes (seminiferous tubules) → passes through epididymis (motility) → vas deferens → prostate (motility) → seminal vesicle (provides nutrition) → bulbourethral gland (lubrication) → urethra → penis Predict how changes in release of pituitary sex hormones will alter oogenesis and spermatogenesis. There is negative feedback. - decrease testosterone leads to increases in FSH and LH - increase testosterone leads to decrease in FSH and LH - decrease in progesterone or estrogen then increase - increase progesterone or estrogen then decrease => use this for contraceptives The ovarian cycle is regulated via negative feedback between the ovaries and the hypothalamus/anterior pituitary. Low levels of estrogen and progesterone stimulate the initiation of a new ovarian cycle and follicular development. Birth control pills maintain constant levels of estrogens and/or progesterone so that the hypothalamus decreases release of GnRH blocking a surge in LH and ovulation does not occur. WEEK 4 LEARNING OBJECTIVES Identify critical cells involved in auditory and visual sensory transmission to the brain. Auditory - Hair cells: specialized mechanoreceptors that sense movement and vibration. - Hair cells that detect sound vibrations are found in the cochlea and those that are part of the vestibular system that sense gravity and motion are found in the semicircular canals - Hair cells do not fire action potentials, but they release neurotransmitters which affect the firing rate of adjacent neurons when they’re depolarized. - Stereocilia: hair-like projections from the surface of the hair cell that move in response to vibration. - Their motion causes depolarization of the cell's membrane by opening or closing ion channels - Sterocilia cannot move on their own. Visual - Opsin: light-sensitive protein that converts light energy into electrical signals in receptor cell - They are G protein-coupled receptors, meaning they activate G proteins which lead to a cellular response with Opsin, the cellular response is a change in membrane potential. - Cone cells: photoreceptor cells that contains opsins sensitive to different wavelengths of light - Provide the sharpest vision, color, found in fovea - Rod cells: sensitive to light but most sensitive to blue-green light (gray shades) → found in periphery - Bipolar cells: receive input from rod and cone cells and releasing

neurotransmitters (do NOT fire action potentials) - Ganglion cells: located in front of the retina and receive input from bipolar cells. - If activated, ganglion cells transmit action potentials by the optic nerve to the visual cortex in the brain to begin processing images Rods,Cones, and Bipolar cells generate graded potentials while ganglia cells generate the action potentials. Describe how hair cells function to transduce mechanical signals to the brain. Hair cells have stereocilia that project from the surface that move in response to vibrations and cause an opening or closing of ion channels → ability to balance and hear. While they do not fire action potentials themselves, the depolarization causes a release of neurotransmitters that alter the firing rate of adjacent neurons. Sense of motion → the vestibular system is made up of two statocyst chambers and three semicircular canals. Hair cells are located within the semicircular canals and provide a sense of gravity and angular motion because as the head rotates, the fluid in the canals causes the stereocilia to move and therefore activate sensory neurons. Ability to hear → hair cells affect our ability to hear by converting pressure waves into an electrical impulse that is sent to the brain. Sound is received by outer ear => sent to eardrum => amplified by 3 middle ear bones (larger size of eardrum compared to oval window)=> vibrations of oval window cause fluid pressure waves in basilar membrane and cochlear duct => cochlear duct contains organ of corti with stereocilia supported by the basilar membrane but projected into tectorial membrane. Vibrations cause movement of the basilar membrane which bends stereocilia because they are projected into unmoving tectorial membranes. When stereocilia bend against the tectorial membrane it causes depolarization and release of neurotransmitters. When stereocilia bend in the opposite direction, hair cells repolarize and do not release neurotransmitters. Describe parts of a simple reflex circuit. (1) Particular tendon is activated (physician strikes tendon with hammer) (2) Stretch receptors in extensor muscles respond by sending signals along the sensory nerve. (3) Sensory neuron synapses with motor neurons in the spinal cord. (4) Motor neurons send excitatory signals to the same extensor muscle, which responds by contracting. (5) An inhibitory interneuron inhibits contraction of opposing flexor muscle Need to inhibit others because muscles can only contract and not pull or push. When one muscle is activated the other is inhibited → flexor stimulated, extensor inhibited when bringing your hand/knee towards body, revered if bring away from body

Explain how the processes of vision and hearing occur. Vision involves a complicated process of converting light signals into images in the brain. Light passes through the lens, where it is focused, to the retina where photoreceptors called rods and cones convert the information to electrical impulses that can be interpreted by the brain. Rod/Cone cells detect light, Rod/Cone cells stop sending neurotransmitters to bipolar cells, which in turn begin to release neurotransmitters, causing ganglion cells to fire off action potentials that signal the visual cortex in the brain. (as release of glutamate closes the cation channel of bipolar cells, which causes it to become hyperpolarized). Sound (hearing), funnels into the ear canal and causes the eardrum to move. Sound vibrations move through the ossicles to the cochlea. Sound vibrations cause the fluid in the cochlea to move.The auditory nerve sends signals to the brain where they are interpreted as sounds. Sound waves travel through the auditory canal, eventually hitting the tympanic membrane. The membrane vibrates, causing the 3 middle ear bones to vibrate. The last bone hits the oval window that moves the fluid in the cochlea. The hair in the cochlea bend one way or another depolarizing/hyperpolaizing and releasing neurotransmitters that cause an action potential in later cells that send a signal to the auditory cortex. Evaluate the molecular effect of a stimulus on a sensory pathway. A stimulus causes some sort of conformational change that allows neurotransmitters to be released, usually turning the pathway on. Predict how changes in a sensory pathway will affect sensory perception. If you affect one part of the pathway (cut off hearing nerve), anything that doesn't allow the pathway to connect to the sensory nerve that sends signals to the brain will cause there to be no perception of the stimulus. Describe the structure and function of a neuromuscular junction. A neuromuscular junction is a synapse between a motor neuron and a muscle where the neurotransmitter is acetylcholine. The function of acetylcholine is to cause muscle contraction when activated. **acetylcholine is found at the synapse. - Consists of a motor neuron synapsing with muscle fiber. - Various channels that open/close to let in certain ions. - Results in the release of neurotransmitters (ACh) that depolarize muscles cells by opening Na+ channels and allows SrR to release calcium, which binds to troponin and removes tropomyosin from actin so myosin can undergo crossbridge cycle 1. Action potential reaches synaptic terminal → change in voltage 2. Voltage gated calcium channels open and calcium flows in 3. Calcium binds to vesicles with neurotransmitter acetylcholine, vesicles fuse with membrane → exocytoses acetylcholine 4. Acetylcholine binds to the ligand-gated ion channels in muscle cell 5. Potassium flows out and sodium flows in → Na+ channels open => depolarization → action potential 6. Depolarization causes voltage-gated sodium channels to open 7. More sodium comes in 8. Action potential propagates down T-tubules → calcium released from sarcoplasmic reticulum 9. SR release Ca2+, which bind to troponin in thin filament (actin), which moves

tropomyosin from the binding sites of myosin 10. Exposure of myosin-binding sites on actin allows cross-bridge as myosin (thick filament) can now attach to produce shortening of muscle (contraction) 11. After AP, Ca2+ moves back to SR and tropomyosin covers actin again, after contraction ends and muscle relaxes Identify cellular, molecular, and protein components involved in muscle contraction and explain their role. Muscle cell - cell that contracts Motor cell - cell that relays signal to muscle cell to contract through the release of acetylcholine Actin filaments - (thin filaments) double helix that is encased by protein tropomyosin Myosin filaments - (thick filaments) myosin heads sticking out Calcium - stored in sarcoplasmic reticulum, binds to troponin → change in shape Troponin - bound to tropomyosin Tropomyosin - wound around actin, blocking myosin binding sites ATP - helps myosin head move and detach from actin Action Potential in muscle - allows influx of Na+ions depolarizing the cell and allowing opening of ca2+ channels Muscle fiber - elongated cells that use ATP generated through ATP Relate the structure of skeletal muscle to its function in generating a contractile force. Larger muscles with more fibers produce greater forces Muscle force is depending on the state already in. - Whole muscles are made of muscle fibers. - Muscle fibers use ATP. - Muscle fibers contain hundreds of long, rodlike structures called myofibrils. - Myofibrils contain parallel arrays of actin and myosin filaments that cause a muscle to contract - Sarcomere is found here. - Sarcomeres are arranged along the length of the myofibril. - The region from one Z disc to the next. Actin subunits: thin filament (double helix with troponin and tropomyosin), lie more on the outside of the sarcomere Myosin: thick filament, lie in the center of the sarcomere The thick and thin filaments slide with respect to one another, using ATP as a source of energy. As a result of the sliding, the Z discs are pulled closer together (shortening results from sliding of actin thin filaments relative to myosin thick filaments) → causing contraction The contraction of a whole muscle fiber results from the simultaneous contraction of all of its sarcomeres → When Ca 2+ is present, this cycling of cross bridges continues and the filaments continue to slide with respect to one another. When Ca 2+ goes back into the sarcoplasmic reticulum, the contraction stops. Striated muscles are arranged into muscle bundles.

Slow twitch muscle fibers: - contract slowly and consume less ATP (greater resistance to fatigue) -- olympic marathoner - Have mitochondria to supply ATP to muscle fibers by aerobic respiration - Have a lot of myoglobin => look Red - Because they can provide their own source of energy, slow-twitch fibers can sustain force for an extended period of time, but they are not able to generate a significant amount of force. - Slow-twitch fibers have a low activation threshold, meaning they are the first recruited when a muscle contracts. If they can't generate the amount of force necessary for the specific activity, the fast-twitch muscle fibers are engaged. Ex: The tonic muscles responsible for maintaining posture have a higher density of slow-twitch fibers. Steady-state endurance training can help increase mitochondrial density, which improves the efficiency of how the body uses oxygen to produce ATP Tetanus == Muscle contraction of sustained force, calcium use does not increase but is maintained at steady concentration WEEK 5 LEARNING OBJECTIVES Explain the relationship between surface area-to-volume ratio and gas exchange efficiency. The rate of diffusion is directly proportional to the surface area over which exchange occurs and to the concentration difference. The rate of diffusion is inversely proportional to the distance over which the molecules move. Greater surface area to volume ratio→ easier to diffuse across membrane (rate of diffusion is directly related to surface area), more efficient gas exchange Describe the changes in muscle contraction, volume, and pressure that occur during ventilation. Tidal Ventilation: air is drawn into lungs during inhalation and air is released from lungs during exhalation Inhalation: Diaphragm contracts (moves down) - thoracic cavity expands (volume expands/increases)→ air pressure in lungs is less than outside of lungs → air is drawn in (inhalation) - negative pressure draws air into the lungs - More volume => less pressure Exhalation: Diaphragm expands/relaxes (moves up) - thoracic cavity contracts (volume decreases) → air pressure in lungs is higher than outside of lungs → air is pushed out - positive pressure forces air out of the lungs - Lower volume => high pressure For relaxed breathing, the diaphragm controls the inhalation and the exhalation is the product of elastic recoil of the lungs and chest wall.

Relate partial pressure and Boyle's Law to ventilation and gas exchange. Partial Pressure: fractional concentration of gas multiplied by the total atmospheric pressure (fractional concentration relative to other gases) X (atmospheric pressure) Boyle's law: pressure of a gas increases, as volume of container decreases; the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature In lung: Increase volume --> lower partial pressure (inhalation) Decrease volume => increase partial pressure (exhalation) Air pressure in lungs compared to air pressure outside of lungs determines whether air is coming in or out → Gases always travel from an area of higher partial pressure to an area of lower partial pressure Reason why pO 2 changes as go up, the O 2 concentration is not changing, but the atmospheric pressure is → sea level => more pressure => so higher partial pressure Higher elevation => less pressure => less partial pressure Explain how the nervous system regulates breathing and how this relates to homeostasis. Homeostatic Control of Breathing: Oxygen and CO2 are homeostatically regulated. Stimulus: O2 level decrease/fall and CO2 levels increase/rise Sensors: Chemoreceptors - (in brain) sense CO2 and H+ concentrations Aortic bodies - (in heart in the aorta) sense O2 and H+ concentration in blood going into the body Carotid bodies - (in neck) sense O2 and H+ concentration in blood going to the brain Sensors detect decreases in O2 levels and increase CO2 levels. Effector: → stimulate motor neurons → activate respiratory muscles and diaphragm to contract more strongly or more frequently (stronger and faster breathing) Response: decreased levels of CO2 increased levels of O2 in blood Most important factor in control of breathing is amount of CO2 in blood Describe how hemoglobin binds oxygen and how this relates to gas exchange. Hemoglobin: protein in red blood cells that binds to oxygen B/c oxygen becomes bound to hemoglobin, the pO2 in the red blood cell is lower than the pO2 in the plasma, so O2 keeps diffusing into the cell.