Final Exam Key

Answers are in italics

Multiple choice:   As always, choose the best answer for each multiple-choice question.  Answer on your scantron form.  Each question (except 1) is worth 3 points.

1. Fill in your scantron form as follows:  (2 points)
   • Write in your name in the upper left (last name first) and bubble it in.
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   1. I get the idea already – give it a rest!
   2.  – e.  I’m using a number 3 pencil, so none of these marks will be read by the machine anyway.
       
2. Consider a person sitting in a bathtub of water.  Which of the following would be considered part of Claude Bernard’s “internal environment”?
   1. The person’s interstitial fluid.
   2. The cytosol of the person’s cells.
   3. The water in the bathtub.
   4. Two of the above.
   5. All of the above.
       
3. In the collection of negative feedback loops controlling thermoregulation, sweat glands would be considered
   1. a sensor.
   2. a setpoint.
   3. an afferent pathway.
   4. an efferent pathway.
   5. an effector.
       
4. In a Donnan equilibrium
   1. the combination of electrical charge and chemical concentration gradient across a membrane are in balance.
   2. only uncharged particles can be involved.
   3. charge builds up because no particles can cross the membrane.
   4. all particles can move across the membrane at the same rate.
   5. conditions are never isotonic.
       
5. At least some water is believed to cross membranes by which of the following routes?
   1. Simple diffusion
   2. Permeation
   3. Facilitated diffusion
   4. Two of the above [a & b]
   5. All of the above
       
6. Every neuron that is not part of the central nervous system can be considered part of the
   1. afferent nervous system.
   2. efferent nervous system.
   3. peripheral nervous system.
   4. somatic nervous system.
   5. autonomic nervous system.
       
7. In a typical cell, you would expect the membrane potential to likely change if
   1. the concentration of Na⁺ outside the cell changed.
   2. the permeability of the membrane to Na⁺ changed.
   3. the surface area of the membrane changed.
   4. Two of the above [a & b]
   5. All of the above.
       
8. A toxin that blocked the voltage-gated sodium channels of neurons would
   1. slow down the depolarization phase of the action potential.
   2. prevent action potentials by keeping the cell from depolarizing.
   3. slow down the repolarization phase of the action potential.
   4. prevent repolarization after an action potential was triggered.
   5. Two of the above.
       
9. An axon with a greater diameter exhibits faster action potential propagation relative to a smaller axon because
   1. a diameter above a threshold value leads to saltatory conduction.
   2. the membrane potential decays more slowly with distance.
   3. ions can flow along the axon more quickly.
   4. they provide a greater membrane surface area, allowing more sodium ions to enter the cell during depolarization.
   5. Axons diameter does not affect the propagation of action potentials.
       
10. A postsynaptic neuron with only one presynaptic neuron would not exhibit which of the following?
    1. Excitatory postsynaptic potentials
    2. Inhibitory postsynaptic potentials
    3. Temporal summation
    4. Spatial summation
    5. All of the above could potentially be seen in this postsynaptic neuron.
        
11. The transduction of an environmental variable by sensory neurons always involves
    1. a change in membrane fluidity.
    2. the activation of G-protein complexes.
    3. a change in the permeability of the membrane to one or more ions.
    4. a substantial change in the intracellular ion concentration.
    5. the up- or down-regulation of mRNA synthesis.
        
12. The refractory period of a sensory neuron is most likely to determine
    1. the lower limit of its dynamic range.
    2. the upper limit of its dynamic range.
    3. the type of variable it can transduce.
    4. Two of the above.
    5. All of the above.
        
13. A drug that hyperpolarized the membranes of photoreceptors would probably cause the recipient of the drug to perceive
    1. nothing but brightness.
    2. nothing but darkness.
    3. red-shifted colors.
    4. blue-shifted colors.
    5. no change in her vision.
        
14. When acting as a hormone, a chemical messenger
    1. reaches only its target tissue or organ.
    2. diffuses to its target.
    3. is carried by the bloodstream to its target.
    4. Two of the above.
    5. All of the above.
        
15. Adrenocorticotropic hormone stimulates the release of
    1. thyroid stimulating hormone.
    2. cortisol.
    3. aldosterone.
    4. corticotropin releasing hormone.
    5. growth hormone.
        
16. A hormone for which the primary role appears to be the inhibition of release of another hormone is
    1. somatostatin.
    2. inhibin.
    3. dopamine.
    4. Two of the above.
    5. All of the above.
        
17. In the calcium regulatory system,
    1. the calcitonin gland responds to high calcium levels.
    2. the calcitonin gland responds to low calcium levels.
    3. calcitonin release causes increased release of calcium from bones.
    4. calcitonin release causes decreased release of calcium from bones.
    5. Calcitonin is associated with audition, not calcium regulation.
        
18. The term that describes an individual muscle cell is
    1. filament.
    2. sarcomere.
    3. muscle fiber.
    4. myofibril.
    5. motor unit.
        
19. A mutation that caused ryanodine receptors to be non-functional would result in
    1. muscles that would not open channels in response to acetylcholine.
    2. muscles that could not propagate action potentials along their surface.
    3. muscle that could not propagate action potentials down their T-tubules.
    4. muscles that would not release calcium in response to an action potential.
    5. muscles that could not resequester calcium.
        
20. The dissociation of myosin and actin after cross-bridge formation requires the presence of
    1. DHP.
    2. ATP.
    3. Ca²⁺.
    4. tropomyosin.
    5. None of these is required for actin-myosin dissociation.
        
21. During an isometric contraction
    1. cross-bridge cycling occurs, the muscle develops force and shortens.
    2. cross-bridge cycling occurs, the muscle develops force but does not shorten.
    3. cross-bridge cycling does not occur, but the muscle develops force and does not shorten.
    4. cross-bridge cycling does not occur, the muscle does not develop force and does not shorten.
    5. “Isometric contraction” is an oxymoron.
        
22. Which of the following would typically be associated with fast glycolytic muscles?
    1. Low levels of myoglobin.
    2. Low rates of fatigue.
    3. High glycolytic enzyme activity.
    4. High numbers of mitochondria.
    5. Two of the above. [a & c]
        
23. Smooth muscle fibers in arterioles serve to
    
    1. control blood distribution.
    2. maintain blood pressure.
    3. prevent backflow of blood.
    4. Two of the above. [a & b]
    5. All of the above.
        
24. In humans, maximal cardiac output is about how many times resting output?
    1. 2 to 3.
    2. 5 to 6.
    3. 8 to 10.
    4. 16 to 20.
    5. 25 to 30.
        
25. Blood travels at its lowest velocity in the
    1. arteries.
    2. arterioles.
    3. capillaries.
    4. venules.
    5. veins.
        
26. In people who have been starving for long periods of time, the protein concentration in the blood begins to drop, lowering the total concentration of solutes in the plasma.  Which of the following is the most likely result of this condition on the rate of lymph formation?
    1. Lymph formation would decrease due to a drop in the net osmotic pressure.
    2. Lymph formation would increase due to a drop in the net osmotic pressure.
    3. Lymph formation would decrease due to a rise in the net osmotic pressure.
    4. Lymph formation would increase due to a rise in the net osmotic pressure.
    5. The net osmotic pressure would not change.
        
27. The lungs expand as the thoracic cavity expands because
    1. the compliance of the lungs tends to make them expand.
    2. the lungs are attached to the internal surface of the thorax by intrapleural fibers.
    3. the air pressure in the lungs is generally greater than it is in the atmosphere.
    4. the pressure in the intrapleural space is lower than the pressure in the lungs.
    5. the blood pressure in the lungs causes them to expand.
        
28. Normal, resting inhalation relies on activation of
    1. the diaphragm.
    2. the external intercostals.
    3. the internal intercostals.
    4. Two of the above
    5. None of the above
        
29. Based on your knowledge of alveolar ventilation, the partial pressure of oxygen in the lungs
    1. can never rise above 104 torr.
    2. can rise above 104 torr but can never reach 160 torr (atmospheric levels).
    3. can reach 160 torr.
    4. can exceed 160 torr due to offloading from hemoglobin.
    5. can exceed 160 torr due to offloading from myoglobin.
        
30. In blood equilibrated with oxygen at normal alveolar partial pressure, the amount of oxygen dissolved in the plasma is about what fraction of the amount bound to hemoglobin?
    1. 1%
    2. 5%
    3. 10%
    4. 15%
    5. No oxygen dissolves in the plasma.
        
31. Based on your knowledge of a typical oxygen saturation curve (and perhaps the ventilatory response to decreased P_O2), if the partial pressure of oxygen drops from 105 torr to 90 torr, the decrease in the percentage of hemoglobin bound to oxygen would likely be about
    1. 5%
    2. 20%
    3. 40%
    4. 60%
    5. 95%
        
32. If the ventilation rate of the lungs is not sufficient, generally the most immediate cause of increased ventilation in response is the levels of which substance in the blood?
    1. Oxygen
    2. Deoxygenated hemoglobin
    3. Carbon dioxide
    4. Hydrogen ions
    5. Bicarbonate ions
        
33. An organ in which no digestion takes place is the
    1. mouth.
    2. stomach.
    3. small intestine.
    4. large intestine.
    5. Two of the above.
        
34. The absorption of glucose from the small intestine is generally via
    1. simple diffusion.
    2. permeation.
    3. symport transport with Na⁺.
    4. antiport transport with K⁺.
    5. glucose ATPase.
        
35. The digestion of fats is carried out by chemicals secreted by the
    1. stomach.
    2. small intestine.
    3. pancreas.
    4. lacteals.
    5. Two of the above.
        
36. For most tissues, post-absorptive activities are initiated by
    1. high levels of glucagon.
    2. low levels of glucagon.
    3. high levels of insulin.
    4. low levels of insulin.
    5. None of the above.
        
37. The initial product of glomerular filtration could best be described as
    1. water.
    2. water and ions.
    3. water, ions and urea.
    4. blood plasma minus the larger proteins and cells.
    5. blood plasma minus the cells.
        
38. Which region of the nephron does not have sodium transporters?
    1. Proximal tubule
    2. Descending limb of the loop of Henle
    3. Ascending limb of the loop of Henle
    4. Distal tubule
    5. All of the above have sodium transporters.
        
39. The most important function of the loop of Henle is
    1. creation of the glomerular filtrate.
    2. reabsorption of a variety of substances from the urine.
    3. secretion of a variety of substances from the urine.
    4. creation of a strong osmotic gradient in the medulla.
    5. control of final urine concentration.
        
40. The release of anti-diuretic hormone will increase if
    1. blood pressure decreases.
    2. plasma osmolarity increases.
    3. alcohol intake increases.
    4. caffeine intake increases.
    5. Two of the above [a & b]
        
41. If a person were injected with a substance that completely inhibited the release of aldosterone, then the release of renin would have no effect (either directly or indirectly) on
    1. angiotensinogen.
    2. sodium absorption in the distal tubule.
    3. blood pressure.
    4. Two of the above.
    5. All of the above.
        
42.  In response to decreasing blood pressure, increased sympathetic activity causes (among other things)
    1. increased arteriolar constriction.
    2. increased stroke volume.
    3. increased ADH release.
    4. Two of the above.
    5. All of the above.
        
43. In a human fetus, the development of the Müllerian ducts into part of the female reproductive tract requires
    1. the presence of testosterone.
    2. the absence of testosterone.
    3. the presence of estrogen.
    4. the absence of estrogen.
    5. None of the above conditions is required for the development of the Müllerian ducts.
        
44. In men, testosterone is produced primarily by the
    1. prostate gland.
    2. Sertoli cells.
    3. Leydig cells.
    4. spermatogonia.
    5. spermatozoa.
        
45. In humans, fertilization usually takes place in the
    1. ovary.
    2. oviduct.
    3. uterus.
    4. vagina.
    5. test tube.
        
46. The defenses provided by various body surfaces would probably be least effective against
    1. viruses.
    2. bacteria.
    3. cancerous cells.
    4. single-celled parasites.
    5. multi-celled parasites.
        
47. C3b is one example of the system known as the
    1. phagocyte system.
    2. neutrophil system.
    3. cytokine proteins.
    4. complement proteins.
    5. chemotaxic proteins.
        
48. The specific immune system differs from the nonspecific defense systems in that
    1. the specific immune system attacks only living cells.
    2. the specific immune system does not kill target cells.
    3. the specific immune system becomes targeted to particular epitopes.
    4. the specific immune system involves only T cells.
    5. the specific immune system involves only antibodies.
        
49. Killer T cells
    1. are derived from helper T cells.
    2. die in the process of killing the cells they attack.
    3. kill cells via the membrane attack complex.
    4. attack virus-infected and cancer cells without needing to recognize an antigen.
    5. do not appear unless interleukin-2 has been released.
        
50. Antibodies are involved in all of following except
    1. neutralization of bound antigens.
    2. enhancement of phagocytosis.
    3. agglutination of antigens.
    4. activation of helper T cells.
    5. Antibodies are involves in all these processes.
        
51. In comparison to the primary immune response, the secondary response
    1. becomes active more quickly.
    2. involves more immune cells.
    3. lasts longer.
    4. Two of the above.
    5. All of the above.
        

Short answer:   Write a concise answer to each of the following questions.  Your answers should fit in the spaces provided.  Each question is worth 4 points.  If you are uncertain about the nature of the question, please ask! 

52. Consider two volumes of water, A and B, separated by a membrane permeable to water but not any solutes.  If A has dissolved in it NaCl at 500 mOsm, while B has urea at 500 mOsm, what can you say about the relative osmolarity and tonicity of the two sides?  Explain your answer.
    
    By definition, the two sides are isosmotic - both are 500 mOsm. Tonicity reflects water movement. Since solutes cannot cross the membrane, the concentration on both sides will stay the same, so water will not move. Therefore the solutions are also isotonic.
    
    
53. Give two characteristics of fast neurotransmitters and two characteristics of slow neurotransmitters.
    
    Fast: ~1ms diffusion time, smaller neurotransmitter molecules, synaptic vesicles attach to bottom of axon terminal, generally involve direct opening of channels. [Other answers possible]

    Slow: >100ms, larger neurotransmitter molecules (usually amino acid based), synaptic vesicles attach to sides of axon terminal, generally involve indirect opening of channels via G-proteins. [Other answers possible]
    

54. Discuss the hormonal control of growth during puberty.  Be sure to consider the effects of both growth hormone and sex hormones.  You do not need to discuss sexual maturation.
    
    During puberty, the large increase in sex hormones causes increased release of growth hormone. This increase in GH results in a growth spurt, including especially the growth of bones. But sex hormones ultimately cause the epiphyseal plates of the long bones to cease growth, so that no further change in height occurs even with continued release of growth hormone.
    
    
55. Describe the mechanical events in the heart during a heartbeat cycle.  You do not need to discuss action potentials, pacemakers, etc.
    
    Starting from all chambers in the relaxed state, the atria contract, increasing blood pressure and forcing open the atrio-ventricular valves so that blood moves from the atria to the ventricles. After a delay of about 0.1 sec, the ventricles begin contracting. Once pressure in the ventricles exceeds that in the atria, the AV valves close again. Pressure builds up in the ventricles as contraction continues (isovolemic contraction), until the pressure in the ventricles exceeds that in the arteries and the pulmonary and aortic valves open. Blood is ejected into the arteries until ventricular contraction ends. As the ventricles relax and pressure in the ventricle drops below that in the arteries, the P & A valves close again. Continued relaxation of the ventricles finishes the cycle.
    
    
56. The partial pressure of carbon dioxide in a closed, half-filled bottle of Mountain Dew is 250 torr.  The bottle has been unopened for a few days, so everything is at equilibrium.
     
    1. If the total pressure in the air-filled portion of the bottle is 1000 torr, what is the fractional content of carbon dioxide?
       
       F_CO2 = P_CO2 / P_Total giving F_CO2 = 250 torr / 1000 torr = 0.25
       
       
    2. If the solubility of carbon dioxide is 0.75 ml/(liter·torr), what is the concentration of carbon dioxide is the Mountain Dew itself?
       
       C_CO2 = P_CO2 x S_CO2 giving C_CO2 = 250 torr x 0.75 ml/(liter·torr) = 187.5 ml/liter
        
57. What are the three major forms of carbon dioxide transport in the blood, and about what percent of the total CO₂ is carried in each form?
    
    Bicarbonate ion: ~70%
    Carbamino compounds: ~23%
    Dissolved in plasma: ~7%
    
    
58. Describe or diagram the two feedback loops that control the activity of the stomach.
    
    The two feedback loops we discussed are those involving the hormones gastrin and secretin. In the case of gastrin, the presence of peptides and the distension of the stomach cause its release. Gastrin then triggers the release of acid and pepsin, which break down the food helping to remove the stimulus. In addition, high H+ levels inhibit further gastrin release, regulating H+ levels. Secretin release in controlled by H+ in the small intestine. Higher acidity increases secretin release, which decreases release of H+ by the stomach, as well as decreasing the rate of stomach emptying.
    
    
59. Give possible causes of
     
    1. metabolic acidosis (2 examples)
       
       Lactic acid buildup (from exercise), diarrhea, protein metabolism
       
       
    2. metabolic alkalosis
       
       Vomiting
       
       
    3. respiratory acidosis
       
       Asthma (or other respiratory disorder)

       [Other answers are possible for all these]
        

60. During pregnancy in humans, which hormones must be maintained at high levels in the mother, and what mechanisms maintain these high levels?
    
    Estrogen and progesterone must remain at high levels (to maintain the endometrial layer). In the first three months or so of pregnancy, these hormones are released by the corpus luteum, which is kept from disintegration by the release of chorionic gonadotropin by the fetus (first from the trophoblast, then the placenta). From 3 months on, the fetus itself produces the estrogen and progesterone in the placenta, and the corpus luteum degenerates.
    
    
61. Answer a. and b. using the graph below. The plot shows the blood levels of luteinizing hormone during the female reproductive cycle.
    
    
    1. Draw and label the approximate blood hormone levels of estrogen and progesterone during the cycle.
        
    2. For each of the following events, place the corresponding number at the appropriate time on the graph.
        
       1. Of the multiple follicles that started development, one becomes dominant at this time. This happens about day 7.
       2. Corpus luteum disintegrates. This happens about days 25-28.
       
        
62. What causes the redness and edema that accompany the inflammatory response?
    
    The redness is caused by increased vasodilation in the region, which causes increased bloodflow. The edema is caused by the increased pore size in the capillaries, which allows more plasma (plus immune cells) to leave the blood and enter the surrounding tissues.
    
    
63. Describe the humoral (B cell) immune response.  How are B cells activated, and what are the results of their activation?  You do not need to discuss memory B cells.
    
    B cells are activated by the presence of antigens that match their particular antigen receptor. In the case of some antigens (like those from bacteria), no further stimulus may be needed, but for many antigens the cytokine interleukin-2 (from helper T cells) is also needed. Once activated, B cells become plasma cells and proliferate. These plasma cells then shed antibodies, which promote destruction of the antigen in a number of ways (deactivation, promotion of phagocytosis, etc).
    
    Extra credit question (4 points)
64. The medical condition known as shock is “failure of the cardiovascular system to keep adequate blood circulating to the vital organs of the body.”  One of the symptoms of shock or impending shock is pale, cool skin.  Why would the astute physiology student be unsurprised by this symptom?
     
    Shock, in other words, is the result of a critical drop in blood pressure. In the short term, the response to such a drop is to try to increase cardiac output and increase peripheral resistance. If resistance in the arterioles of the skin is greatly increased, this will help defend BP, but will also result in reduced blood flow to the skin - hence its pale, cool nature in a shock victim.