Introduction to Section II - Creighton University



Biology 449 - Animal Physiology Spring 2006

Midterm 2

Fill in your scantron form as follows:

• Write and bubble in your name in the upper left, last name first.

• Follow any additional instructions provided in class.

• Sign your form in the upper right.

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

1. In the phrase “excitation-contraction coupling,” the “excitation” refers to

a. the release of neurotransmitter by the motor neuron.

b. the depolarization of the muscle membrane (sarcolemma).

c. the release of calcium ions from the sarcoplasmic reticulum.

d. cross-bridge cycling.

e. ATP production.

2. The release of calcium ions from the sarcoplasmic reticulum of a muscle during the excitation-contraction process occurs via

a. simple diffusion through the membrane of the SR.

b. diffusion though calcium channels in the SR.

c. primary active transport of Ca2+ out of the SR via a uniport carrier protein.

d. secondary active transport using a Ca2+/K+ antiporter in the SR.

e. Ca2+ does not leave the SR during the excitation-contraction process.

3. Imagine a sarcomere with shorter than normal thick filaments. The bare zone is the same size as normal, but there are fewer myosin molecules present in the filament. Which of the following best describes the expected length-tension relationship for the sarcomere, in comparison to a normal sarcomere?

a. The sarcomere could produce less maximum force than normal, but could get longer than a normal sarcomere before net force production dropped to zero.

b. The sarcomere could produce less maximum force than normal, but could get shorter than a normal sarcomere before net force production dropped to zero.

c. The sarcomere could produce a greater maximum force than normal, and could get longer than a normal sarcomere before net force production dropped to zero.

d. The sarcomere could produce a greater maximum force than normal, and could get shorter than a normal sarcomere before net force production dropped to zero.

e. Sarcomeres got myosin?

4. While a muscle is at rest, cross-bridge cycling does not occur because myosin binding sites on actin

a. don’t have the correct molecular charge.

b. are in the low energy conformation.

c. are blocked by calcium ions.

d. are blocked by troponin.

e. are blocked by tropomyosin.

5. Which of the following shows the expected characteristics of a fast-glycolytic fiber relative to other muscle fiber types?

|Contraction |Mitochondrial |Myosin ATPase |Primary Metabolic |

|Velocity |Density |Activity |Pathway |

a. High High High Anaerobic

b. Low High High Anaerobic

c. High Low High Anaerobic

d. High High Low Anaerobic

e. High High High Aerobic

6. The muscle fibers in a single motor unit

a. are all the same fiber type.

b. are innervated by multiple neurons.

c. are activated in sequence, with new fibers initiating contracting as old ones fatigue.

d. are fused together into a single super-cell.

e. Two of the above.

7. In comparison to arteries, veins

a. carry blood under higher pressure.

b. carry blood showing a more pulsatile flow pattern.

c. have a larger average diameter.

d. have walls made of only one cell layer.

e. always have blood with a lower oxygen content.

8. Blood travels to the head via

a. the carotid arteries.

b. the coronary arteries.

c. the hepatic arteries

d. the iliac arteries.

e. the subclavian arteries.

9. Which of the following best describes the pattern of cardiac cell depolarization?

a. All cardiac cells spontaneously depolarize in a coordinated manner.

b. Although all cardiac cells can spontaneously depolarize, the pacemaker cells depolarize first; depolarization of other cardiac cells is then triggered by AP’s arriving from adjacent cells.

c. Only pacemaker cells can spontaneously depolarize; depolarization of other cardiac cells is triggered by AP’s arrived from adjacent cells.

d. Pacemaker cells are depolarized by neurons; depolarization of other cardiac cells is triggered by AP’s arrived from adjacent cells.

e. All cardiac cells are depolarized by neurons.

10. Which of the following would be most likely to cause an increase in the rate of lymph formation?

a. an increase in blood pressure in the capillaries.

b. an increase in the osmolarity of the blood.

c. a decrease in the rate of lymph transport by the lymphatic system.

d. Two of the above.

e. All of the above.

11. In the lungs of mammals, gas exchange between the lungs and blood takes place very efficiently because

a. the blood coats the surface of the brochioles.

b. the blood coats the surface of the alveoli.

c. the blood pools around the outside of the alveoli and bronchioles.

d. capillaries wrap around the bronchioles.

e. capillaries wrap around the alveoli.

12. Which of the following statements is correct? During a deep inhalation,

a. the pressure in the intrapleural fluid becomes more negative because the lungs are decreasing in size.

b. the pressure in the intrapleural fluid becomes more negative because the thorax is increasing in size.

c. the pressure in the intrapleural fluid becomes more positive because the lungs are increasing in size.

d. the pressure in the intrapleural fluid becomes more positive because the thorax is increasing in size.

e. Two of the above are correct.

13. Breathing through a snorkel or other tube effectively increases a person’s anatomical dead space. If a person were snorkeling and the resulting total dead space (true anatomical + snorkel) was 300 ml, what would be the effect on the alveolar ventilation rate?

a. It would increase by about 100%.

b. It would decrease by about 40%.

c. It would decrease by about 50%.

d. It would be reduced to zero.

e. It is impossible to say without additional information.

14. If the solubility of a gas in water is 0.1 ml/liter·torr, and the concentration of the gas is 10 ml/liter, then the partial pressure of the gas is

a. 0.01 ml

b. 1 ml

c. 0.01 torr

d. 1 torr

e. 100 torr

15. The tendency of a gas to diffuse from one location to another is always directly related to the difference in ____________ between the two locations.

a. concentration

b. fractional content

c. partial pressure

d. solubility

e. volume

16. Each standard hemoglobin molecule can carry up to how many oxygen molecules?

a. One.

b. Two.

c. Four.

d. Sixteen.

e. More than I can count on my fingers and toes.

17. Which of the following statements about blood and alveolar gas content is not true?

a. PO2 is higher in the air than in the alveoli.

b. PCO2 is lower in the air than in the alveoli.

c. PO2 is higher in the systemic arteries than in the systemic veins.

d. PCO2 is lower in the systemic arteries than in the systemic veins.

e. The magnitude of the change in PO2 between the arteries and veins is about the same as the magnitude of the change in PCO2.

[pic]

18. Based on the curve above, if the partial pressure of oxygen in the alveoli of this person was 60 torr, the blood would leave the lungs with what percent saturation of the hemoglobin?

a. 30%

b. 85%

c. 90%

d. 95%

e. ~100%

19. Which of the following might be expected to cause a left-shift in the oxygen saturation curve?

a. a decrease in temperature.

b. a decrease in pH.

c. a decrease in PO2.

d. an increase in PCO2.

e. Two of the above.

20. Consider a two pigment oxygen transport system in which Pigment A brings oxygen to Pigment B. In this case, both pigments have the same oxygen affinity curve. Assuming the two pigments are exposed to each other for sufficient time, which of the following will be true?

a. Pigment A and B will have the same PO2, but Pigment A will have higher oxygen saturation.

b. Pigment A and B will have the same PO2, but Pigment B will have higher oxygen saturation.

c. Pigment A and B will have the same oxygen saturation, but Pigment A will have higher PO2.

d. Pigment A and B will have the same oxygen saturation, but Pigment B will have higher PO2.

e. Pigment A and B will have the same PO2 and the same higher oxygen saturation.

Short answer: Write a concise answer to each of the following questions. Your answers should fit in the spaces provided. Diagrams must be accompanied by written explanations. Each question is worth 8 points.

21. Compare a twitch contraction to a sustained tetanic contraction in the following questions:

a. How is each type of contraction triggered?

b. How do levels of force production compare?

c. What factor(s) cause force production to decrease at the end of each type of contraction? (Assume an effort is being made to sustain the tetanic contraction as long as possible.)

22. The following questions pertain to arteriolar diameter:

a. What three major mechanisms or pathways contribute to the control of vasoconstriction?

b. Assuming no other variables change, what would be the relative change in blood flow to a region if the diameter of arterioles leading to that region increased by 50%?

23. The following questions pertain to the mechanical events that occur during the cardiac cycle:

a. Describe blood pressure, blood flow, and valve activity in the ventricle, and how these events are related, during systole only. You do not need to discuss AP’s, etc.

b. How is pressure in the blood vessels maintained during diastole?

c. If the atrioventricular valve on the left side of the heart (the mitral valve) was leaky (that is, it could not close completely), what do you think would be the effect on blood pressure and flow during systole?

24. Describe the three forms in which carbon dioxide is transported by the blood in humans. Be sure to indicate the proportion of CO2 carried in each form, and the specific chemical form in which the CO2 is transported, when applicable.

25. By creating different mixtures of oxygen, carbon dioxide and nitrogen and asking a person to breath these mixtures, it is possible to temporarily alter the PO2 and PCO2 in the alveoli. What changes in minute ventilation (increase, decrease, no significant change) would you expect to see in a person whose alveolar gas levels were at the levels shown? Explain the basis for your answers below. As a reminder, normal alveolar gases are PO2 = 104 torr, PCO2 = 40 torr.

a. PO2 = 104 torr, PCO2 = 44 torr

b. PO2 = 104 torr, PCO2 = 36 torr

c. PO2 = 90 torr, PCO2 = 40 torr

d. PO2 = 60 torr, PCO2 = 40 torr

e. PO2 = 60 torr, PCO2 = 36 torr

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