W3006 '00 Physiology Problem Set #8 Cardiovascular system

1. A person's heart starts to beat very fast. A physician presses on the neck, where the carotid artery is. Describe the pathway by which this leads to a slowing of the heart rate.

2. Which of the following would cause the greatest change in blood flow? a. doubling the radius of the vessel b. doubling the difference in pressure gradient within the vessel c. doubling the viscosity of the blood d. doubling the length of the vessel

3. Decreased stroke volume ____ heart rate. a. increases b. decreases c. has no effect on

4. Since fibrinogen is always present in the blood, but the blood doesn't clot, _____ must normally be absent. a. prothrombin b. thrombin c. platelets d. plasmin

5. The Framingham Study and the Seven Countries Study both looked at the question whether dietary fat is related to cardiovascular disease. List the advantages and disadvantages of using each of these types of studies to answer that question.

6. A. In a study of the effects of dietary fat on behavior of monkeys, Kaplan et al compared response to diets with the human dietary equivalent of 60 g cholesterol/day and 1600 g cholesterol/day. The average American today eats a diet of about 400 mg/day. Why did the scientists use these extreme diets? B. Kaplan found that monkeys on a high cholesterol diet were less aggressive than those on the low cholesterol diet. A recent study of middle-age men in Finland found that people with high cholesterol were more aggressive than those with low cholesterol. . Should we conclude from this report that the results of Kaplan's study are not applicable to humans?

7. You withdraw blood from a healthy person and put it in a testtube; it soon forms a blood clot (fibrin clot). You perform the same test on two hemophiliacs and get the following results: Plonie's blood: Doesn't clot Almonie's blood: Doesn't clot Plonie & Almonie's blood mixed together: Does clot. Explain why mixing the blood of two hemophiliacs may cause their usually non-clotting blood to form a clot.

8. Explain why a person with a damaged liver may have problems if there's damage to a blood vessel.

9. If nerves from the arterial baroreceptors are cut, blood pressure will increase/decrease/not change? Explain

12. Dean Ornish found the following results for blockage of arteries in experimental subjects who adhered to the lifestyle regimen he devised. Percent of vessel that was blocked: Experimental group: before: 40.0 after: 37.8. Control group: before: 42.7 after: 46.1 (p=0.001) What theoretical consideration would lead you to predict that these small changes which were statistically significant, were also biologically significant?

13. When a heart is transplanted, it takes a few months for neurons to re-grow and innervate the new SA node. However, even before this innervation occurs, the heart is able to increase cardiac output in response to exercise. Explain how this might work.

14. Dopamine-beta-hydroxylase deficiency is a congenital disorder. (This enzyme converts dopamine to norepinephrine.) One symptom is that a person feels dizzy and has a drop in blood pressure upon standing up suddenly. Explain why this occurs.

15. Before they reach menopause, women are less likely to develop atherosclerosis than are men. This is most likely due to the ability of estrogen to a. increase the number of LDL receptors in the liver b. increase the number of scavenger receptors on macrophages c. increase the synthesis of pancreatic lipase d. increase the synthesis of lipoprotein lipase e. increase the synthesis of apoprotein in the intestinal epithelium

16. Aspirin is thought to decrease risk of heart attack by inhibiting production of thromboxane A2 and thereby preventing a. platelet aggregation b. synthesis of fibrinogen c. a rise in blood pressure d. LDL uptake by liver e. Na+ reabsorption