Introduction to Section II



Biology 449 - Animal Physiology Fall 2008

Midterm 2

Fill in your scantron form as follows:

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

• Sign your form on the upper right. By so doing you verify that you are abiding by Creighton’s policy on academic honesty.

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. A chemical messenger would be classified as a paracrine agent if it

a. reached a target cell via the bloodstream.

b. reached a target cell solely by diffusion.

c. affected the cell that released it.

d. was released by a modified neuron.

e. was a modified form of cholesterol.

2. Epinephrine is secreted by which of the following glands?

a. Adrenal cortex

b. Adrenal medulla

c. Anterior pituitary

d. Gonads

e. Two of the above.

3. Which of the following is/are steroid hormones?

a. Growth hormone

b. Insulin-like growth factor I (IGF-I)

c. Prolactin

d. Sex hormones

e. Thyroid hormones

4. The release of hormones from the anterior pituitary is controlled largely by the release of hormones from the hypothalamus. For which of the following hormones is release directly inhibited by a hormone released from the hypothalamus?

a. follicle-stimulating hormone.

b. growth hormone.

c. luteinizing hormone.

d. prolactin.

e. Two of the above. (b and d)

5. Which of the following shows a correct hormonal pathway?

a. Thyroid stimulating hormone → thyrotropin releasing hormone → thyroid hormones

b. Thyroid stimulating hormone → thyroid hormones → thyrotropin releasing hormone

c. Thyrotropin releasing hormone → thyroid stimulating hormone → thyroid hormones

d. Thyrotropin releasing hormone → thyroid hormones → thyroid stimulating hormone

e. Thyroid hormones → thyroid stimulating hormone → thyrotropin releasing hormone

6. An individual is found to have lower than normal levels of adrenocorticotropic hormone and corticotropin releasing hormone, and higher than normal levels of cortisol. Which of the following would explain this pattern?

a. An autoimmune disease that causes antibodies to inhibit activation of receptors for adrenocorticotropic hormone.

b. An autoimmune disease that causes antibodies to permanently activate receptors for adrenocorticotropic hormone.

c. A tumor in the adrenal cortex that causes it to hypersecrete cortisol.

d. High levels of stress.

e. Two of the above. (b and c)

7. One of the primary mechanisms by which the thyroid hormone pathway increases metabolic rate is

a. increased insertion of Na+/K+-ATPase into cell membranes.

b. increased shivering.

c. increased fatigue.

d. increased growth.

e. increased breakdown of proteins.

8. Recall the relationship between the length of a sacromere and the force produced by the sarcomere during contraction. The reason the force eventually reaches zero as the sarcomere gets longer is that

a. the thin filaments encounter the “bald spot” on the thick filament.

b. the thin filaments start overlapping each other.

c. the thick filaments are being compressed by the Z-line of the sarcomere.

d. the thin and thick filaments no longer overlap.

e. there is insufficient ATP to activate all the exposed myosin heads.

9. The effect of increased Ca2+ levels on troponin is to

a. cause it to lyse into two different molecules.

b. cause it to change conformation.

c. cause its binding site for myosin to become active.

d. cause it to energize myosin heads.

e. cause it to attach to the Z-lines.

10. Consider a muscle lifting two different weights isotonically. If we look at a contraction during which the muscle lifts the heavier weight, compared to one during which it lifts the lighter weight, the contraction for the heavier weight will show

a. a slower shortening velocity, a shorter period of shortening, and less distance shortened.

b. a slower shortening velocity, the same period of shortening, and less distance shortened.

c. the same shortening velocity, a shorter period of shortening, and less distance shortened.

d. a slower shortening velocity, a longer period of shortening, and the same distance shortened.

e. a faster shortening velocity, a shorter period of shortening, and the same distance shortened.

11. The best definition for a “tetanic” contraction is one in which

a. the muscle cannot change its length.

b. the muscle experiences a constant load.

c. only some fibers in a muscle are activated.

d. all the fibers in a muscle are activated.

e. the muscle fibers show continuous action potentials.

12. In a living vertebrate (as opposed to a laboratory preparation), the mechanism used to make a whole muscle produce a small amount of force (relative to its full potential) is

a. a small number of slow oxidative fibers are each fully activated.

b. a small number of fast glycolytic fibers are each fully activated.

c. a large number of slow oxidative fibers are each partially activated.

d. a large number of fast glycolytic fibers are each partially activated.

e. all the fibers in the muscle are each partially activated.

13. Blood pressure is normally lowest in which part of the systemic circuit?

a. The arteries

b. The capillaries

c. The venules

d. The veins

e. Pressure is approximately equal in all these places.

14. In a healthy mammalian heart, the heartbeat is initiated by action potentials in the

a. atrial contractile muscle.

b. atrioventricular node.

c. sinoatrial node.

d. venoatrial node.

e. autonomic nervous system.

15. Which of the following statements about the systemic versus pulmonary circuits of the circulatory system is not true?

a. Blood pressure is greater in the systemic circuit.

b. Resistance is greater in the systemic circuit.

c. Blood flow is greater through the systemic circuit.

d. Two of the above are not true.

e. a, b, and c are all true.

16. Sitting in a hot bath tends to cause strong cutaneous vasodilation. Given this, which of the following statements is most likely correct, assuming no other changes in cardiovascular function occur?

a. Blood flow to the skin will increase, blood pressure will increase, and blood flow to other tissues will increase.

b. Blood flow to the skin will increase, blood pressure will increase, and blood flow to other tissues will decrease.

c. Blood flow to the skin will increase, blood pressure will decrease, and blood flow to other tissues will decrease.

d. Blood flow to the skin will decrease, blood pressure will increase, and blood flow to other tissues will increase.

e. Blood flow to the skin will decrease, blood pressure will increase, and blood flow to other tissues will decrease.

17. According to Poiseuille’s Law, doubling the pressure difference between the upstream and downstream ends of a length of tubing would cause the flow to

a. decrease by 16-fold.

b. decrease by two-fold.

c. increase by two-fold.

d. increase by 16-fold.

e. The flow would not change in response to a change in the pressure gradient.

18. In active hyperemia, endothelial cells of blood vessels release nitric oxide

a. to promote vasoconstriction.

b. in response to high oxygen levels.

c. in response to low H+ levels.

d. in response to low CO2 levels.

e. to cause relaxation of smooth muscles.

19. Which of the following substances can diffuse directly through the membranes of a capillary’s endothelial cells?

a. Na+

b. Oxygen

c. Exchangeable proteins

d. Plasma proteins

e. None of these can diffuse through the endothelial membranes.

20. Which of the following statements about the formation of lymph is true?

a. Hydrostatic pressure driving fluid out of the capillaries is slightly greater than osmotic pressure in the opposite direction, resulting in the formation of about 4 liters of fluid per day.

b. Hydrostatic pressure driving fluid into the capillaries is slightly less than osmotic pressure in the opposite direction, resulting in the formation of about 4 liters of fluid per day.

c. Hydrostatic pressure driving fluid out of the capillaries is slightly greater than osmotic pressure in the opposite direction, resulting in the formation of about 40 liters of fluid per day.

d. Hydrostatic pressure driving fluid into the capillaries is slightly less than osmotic pressure in the opposite direction, resulting in the formation of about 40 liters of fluid per day.

e. Lymph is the tears shed by your cells every time you miss a question on a physiology test.

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

21. The following questions address growth in the long bones (such as the femur) of a human.

a. Describe the process by which long bones grow in length.

b. What controls the rate of long bone growth (and thus overall height), and what causes these bones to cease growth?

22. The following table compares fast glycolytic muscle fibers to slow oxidative ones. Fill in each blank with a suitable term indicating the nature of FG muscles relative to SO ones. An example is provided.

| |Relative to |

|Characteristic |SO, FG is |

|Force production |Greater |

|Contraction Velocity |_______________ |

|Myosin-ATPase activity |_______________ |

|Anaerobic capacity |_______________ |

|Mitochondrial density |_______________ |

|Myoglobin concentration |_______________ |

|Glycogen stores |_______________ |

|Rate of fatigue |_______________ |

|Fiber diameter |_______________ |

23. Describe the process of muscle excitation and contraction from the point when an action potential arrives at the axon terminal of a motor neuron (the neuromuscular junction) and ending with the diffusion of Ca2+ into the area containing the thick and thin filaments. You do not need to describe what occurs once Ca2+ reaches the filaments or anything after this point.

24. Describe the mechanical events that occur during ventricular diastole in the mammalian heart. Include both the atria and the ventricles in your discussion, and be sure cause-and-effect relationships are clear. You do not need to describe the electrical events in the heart. Please begin your discussion with the very start of ventricular diastole.

25. Provide a list of the different aspects of the cardiovascular system affected by the sympathetic nervous system, and indicate the result of increased sympathetic activity in each case.

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