Biology 449 - Animal Physiology Fall 2004
Midterm 2
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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. Which of the following would have an internal structure least like the others?
a. A fast glycolytic muscle fiber
b. A fast oxidative muscle fiber
c. A slow oxidative muscle fiber
d. A cardiac muscle cell
e. A smooth muscle cell
2. As a sarcomere contracts from 2 microns down to its minimal size, the force it generates
a. increases because the filaments become more compact as they contract, increasing the density of binding sites.
b. increases because more myosin heads overlap with actin.
c. decreases because thin filaments interfere with each other and thick filaments collide with Z-lines.
d. decreases because ATP cannot effectively diffuse into the sarcomere as filaments overlap.
e. stays the same because none of the above factors changes.
3. When action potentials cease, a muscle fiber stops contracting because
a. calcium diffuses out of the muscle fiber through the sarcolemma.
b. calcium is deactivated by calmodulin.
c. calcium is reabsorbed by ryanodine receptors into the sarcoplasmic reticulum.
d. calcium is taken up into the sarcoplasmic reticulum by active transport.
e. no more ATP is available.
4. The mechanism that prevents cross-bridge cycling in a relaxed muscle is
a. tropomyosin covers the head of the myosin molecule.
b. tropomyosin covers the myosin binding site on actin.
c. tropomyosin interferes with the movement of the myosin head.
d. tropomyosin blocks the ATP binding site on myosin.
e. tropomyosin prevents the dissociation of myosin and actin.
5. A twitch contraction is one
a. involving a single action potential.
b. involving a single sarcomere.
c. involving a single muscle fiber.
d. involving a single weight.
e. involving a fast muscle.
6. Which of the following are associated with fast glycolytic muscle fibers?
a. Low mitochondrial density.
b. Large numbers of fibers per motor unit.
c. Large glycogen stores.
d. Two of the above.
e. All of the above.
7. The number of muscle fibers in an adult’s biceps normally
a. increases over time given increased duration of workouts.
b. increases over time given increased intensity of workouts.
c. increases over time regardless of activity.
d. stays relatively constant.
e. a and b.
8. All blood vessels include
a. an endothelial layer.
b. a layer of smooth muscle.
c. an outer layer of fibrous or elastic connective tissue.
d. a and b.
e. All of the above.
9. When we say the heartbeat is “myogenic,” we mean
a. the heartbeat is triggered by the contraction of muscles.
b. the heartbeat originates in motor neurons.
c. the heartbeat originates in modified cardiac muscle cells.
d. the heartbeat is controlled by the activity of myoglobin.
e. the heartbeat is not influenced by nervous input.
10. Which of the following effects would you expect to result from severing the bundle of His?
a. The depolarization rate of the sinoatrial node would change.
b. The atria would not contract normally.
c. The atrioventricular node would have an increased delay before depolarizing.
d. The ventricles would not contract normally.
e. There would be no noticeable change in the heartbeat.
11. Blood is kept moving in the correct direction through the heart due to the presence of
a. valves between the veins and the atria.
b. valves between the atria and the ventricles.
c. valves between the ventricles and the arteries.
d. Two of the above.
e. All of the above.
12. Which of the following statements about ventricular diastole is not true?
a. The ventricular muscle is relaxed during ventricular diastole.
b. Ventricular pressure drops close to zero during ventricular diastole.
c. No heart valves are open during ventricular diastole.
d. Blood pressure is maintained by arterial elasticity during ventricular diastole.
e. The atria contract during ventricular diastole.
13. Given what you know about arterial blood pressure in the systemic and pulmonary circuits, and what you know about cardiac output, the pulmonary circuit
a. must have lower blood flow than the systemic circuit.
b. must have higher blood flow than the systemic circuit.
c. must have lower resistance than the systemic circuit.
d. must have higher resistance than the systemic circuit.
e. None of the above should be true.
14. Blood velocity (in cm/s) is lowest in
a. the arteries.
b. the capillaries.
c. the veins.
d. a and c.
e. Blood velocity is the same in all areas of the circulatory system.
15. If the diameter of an arteriole doubles, the blood flow through the arteriole will
a. decrease 16-fold
b. decrease 4-fold
c. increase 2-fold
d. increase 4-fold
e. increase 16-fold
16. The force that tends to move fluid out of the blood and through the capillary walls, thus forming lymph, is
a. hydrostatic pressure resulting from the activity of the heart.
b. hydrostatic pressure generated by compression of the capillaries.
c. osmotic pressure resulting from higher protein content in the blood.
d. osmotic pressure resulting from the hemoglobin content of erythrocytes.
e. osmotic pressure resulting from higher protein content in the interstitial fluid.
17. The total surface area of the alveoli in the lungs is on the order of
a. 75 square centimeters (12 square inches).
b. 0.75 square meters (8 square feet)
c. 7.5 square meters (80 square feet)
d. 75 square meters (800 square feet)
e. 7500 square meters (80,000 square feet)
18. At rest rates of ventilation, the pressure in the alveoli during inhalation is
a. exactly the same as the outside air.
b. about 1 torr lower than the atmosphere.
c. about 10 torr lower than the atmosphere.
d. about 100 torr lower than the atmosphere.
e. about zero torr.
19. The lungs “stick to” the inner wall of the thoracic cavity due to
a. collagenous fibers connecting the two.
b. relatively high air pressure in the lungs.
c. the blood pressure in the lungs.
d. relatively low pressure in the intrapleural fluid.
e. the natural tendency of the lungs to expand due to elasticity.
20. The tendency of a gas to diffuse from one location to another can most accurately be determined by
a. the partial pressure difference.
b. the concentration difference.
c. the solubility difference.
d. the affinity difference.
e. the osmotic difference.
21. At rest, the differences in partial pressure between the blood returning to the lungs and the alveoli are about
a. 0 torr for oxygen and 0 torr for carbon dioxide.
b. 6 torr for oxygen and 6 torr for carbon dioxide.
c. 6 torr for oxygen and 65 torr for carbon dioxide.
d. 65 torr for oxygen and 6 torr for carbon dioxide.
e. 65 torr for oxygen and 65 torr for carbon dioxide.
22. Most oxygen is carried in blood
a. dissolved in the plasma.
b. bound to iron atoms in heme groups.
c. bound to heme group as carboxyls.
d. bound to amino groups in globins as carboxyls.
e. in the form of bicarbonate.
23. Increases in levels of which of the following would usually lead to the Bohr effect?
a. Carbon dioxide
b. Lactic acid
c. Temperature
d. Two of the above
e. All of the above
24. The amount of carbon dioxide transported in the blood simply as dissolved gas is
a. less than 10%.
b. about 25%
c. about 50%
d. about 70%
e. greater than 90%.
25. Based on the examples of two pigment systems from lecture, which of the following appears to be true?
a. The second pigment receiving the oxygen has a lower affinity for oxygen than the first pigment.
b. The second pigment receiving the oxygen has about the same affinity for oxygen as the first pigment.
c. The second pigment receiving the oxygen has a higher affinity for oxygen than the first pigment.
d. Two pigment systems do not occur in men.
e. Two 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.
26. Describe the process of excitation-contraction coupling in a muscle fiber, from the arrival of an action potential at the axon terminal of the motor neuron to the release of calcium into the sarcoplasm. You do not need to discuss any of the later events.
27. What factors, as discussed in lecture, control the stroke volume of the heart? Provide a sentence or two describing each of these factors.
28. The figure below shows data recorded during a muscular contraction.
What kind of contraction was measured?
How long is the latent period for this muscle?
When will the muscle begin lifting a 2.5 N weight?
What is the maximum weight the muscle can lift?
29. What is the “anatomical dead space” of the lungs, and what effect does it have on alveolar ventilation?
30. On a spring-break flight down to Puerto Borracho, the jet you are in experiences a sudden pressure loss, resulting in a drop in PO2 in the alveoli to 50 torr. During the initial period after this event (before any physiological responses or saturation curve shifts can take place) about what amount of oxygen (in percent) will be delivered to tissues with a PO2 of 30 torr?
/Answer below
Fifty years later, your grandchild is on a spaceflight to Asteroid Borracho when the ship she is in experiences complete decompression. During the period it takes her to find her helmet, the PO2 in her lungs drops to about zero torr. As blood returning from systemic capillaries first reaches the lungs, what will happen with regard to hemoglobin saturation and oxygen diffusion?
31. In general terms, how do changes in the PCO2 of the blood affect ventilation rates?
How and where is this change in PCO2 actually sensed in the blood (not elsewhere)?
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