W3006 '02 Physiology Problem Set #8 Cardiovascular system: Atherosclerosis and blood pressure
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. 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.
5. 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?
6. If nerves from the arterial baroreceptors are cut, blood pressure will increase/decrease/not change? Explain
7. 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?
8. 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.
9. 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.
10. 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
11. The following appeared in the well known journal (The Annals of Improbable Research): "Scientists found that some people carry a gene that allows them to eat high cholesterol food without increasing their production of low-density lipoproteins (LDL)… One major restaurant chain will soon urge consumers to take the simple blood test that shows whether they carry the gene. Those who do will be eligible for discount coupons for french fries and special high-fat hamburgers." Suggest a mechanism by which this gene might prevent high blood levels of LDLs.
12.Following are several treatments that have been used to treat high blood pressure. For each one, circle the immediate effect of this treatment and why it would lower the blood pressure.
A.Beta-1 adrenergic receptor blocker. (increase or decrease) in (cardiac output or
peripheral resistance)
B.Drug which enables nitric oxide activity (increase or decrease) in (cardiac output or
peripheral resistance)
C.Aldosterone antagonist (increase or decrease) in (cardiac output or peripheral
resistance)
13. The end systolic volume
a. is the volume of blood in the ventricle after it has ejected its blood
b. is the volume of blood in the ventricle after it has filled with blood
c. is always equal to the stroke volume
14. Which is greater X or Y
X. Stroke Volume when End Diastolic Volume is 135 ml.
Y. Stroke Volume when End Diastolic Volume is 155ml
15. The protein SR-B1 which was recently found identified as the HDL receptor, is found in high concentrations in the adrenal gland.
In which part of the adrenal gland is it high?
Why is it high there?
16. There are several longitudinal, cross-sectional and cross-cultural studies that support the hypothesis that a low fat diet decreases the risk of heart disease and cancer. But there are other studies that fail to support this idea. Dale Atrens, an Australian psychologist, argues that given the uncertainty in the benefits of a low fat diet, public health messages to adhere to such an unpleasent diet is "irrational and mischevious" and we have " a great deal to lose from subscribing to a fear riddled and ineffective lifestyle."
Is it likely that the emotional stress caused by giving up steak, french fries and ice cream, cause more heart disease or cancer than the high fat diet would have?
(This hasn’t been researched, so I don’t expect a definitive answer; I expect you to discuss this idea while referring to the specifics from lecture or readings.)
17. Hemorrhage, or loss of blood, stimulates numerous compensatory mechanisms to maintain homeostasis. Hemorrhage causes (an increase)(a decrease) in blood pressure, which (imcreases)(decreases) the frequency of messages from the arterial baroreceptors. This leads to an increase in messages along the (sympathetic)(parasympathetic) nuerons causing a) constriction of (arterioles)(veins)(capillaries) which leads to an increase in arterial blood pressure and b) constriction of (arterioles)(veins)(capillaries) which leads to an increase in end diastolic volume and (increase)(decrease) of cardiac output.
18. A woman has been on a low sodium diet for several days. She is given an injection of a drug that inhibits angiotensin-converting enzyme. Her blood pressure (increases)(decreases) because of (an increase)(a decrease) in arteriolar resistance. Explain including appropriate equations.
19. A certain drug is an alpha 1 receptor agonist (ie, it stimulates the receptor) which can be used to prevent the localized edema that occurs in the nasal passages during allergic responses.
This drug should directly increase/decrease/not affect the strength of the heart contraction. Explain.
20. Is sugar consumption related to heart disease? To answer this question, Yudkin and Roddy asked two groups of patients about their usual intake of food. The results are as follows.
| Category | Sample Size | Average sugar consumption (g/day) |
| Patients recovering from heart attack | N=20 | 132 |
| Patients recovering from broken bone | N=25 | 77 |
Yudkin and Roddy concluded that sugar is likely to be a cause of heart disease. However there are other conclusions that are compatible with the data. List three reasons why you would be hesitant to accept their conclusion, including possible confounding factors.
21. Certain bacteria can induce an extreme reaction in which the body releases excessive amounts of cytokines. Rather than causing vasodialtion just locally, in this case extensive vasodilation occurs in all the blood vessels in the body. Explain why this is dangerous.
22. A sudden increase in the pressure in the carotid sinus leads to ______ sympathetic nerve activity. (increased)(decreased)