PRACTICE QUESTIONS

1. A change from breathing normal air (21% O₂ and 0.04% CO₂) to breathing a gas mixture of 10% O₂ and 5% CO₂ would cause pulmonary blood vessels to_________________

and pulmonary resistance to________________________.

a. constrict; increase

b. constrict; decrease

c. dilate; increase

d. dilate; decrease

e. remain unchanged; remain unchanged

2. If aortic compliance decreases while heart rate, cardiac output, and total peripheral resistance (TPR) remain unchanged:

a. Pulse pressure will be unchanged.

b. Pulse pressure will increase.

c. Pulse pressure will decrease.

d. One cannot know the effect on pulse pressure because stroke volume may have changed.

e. One cannot know the effect on pulse pressure because mean aortic pressure may have changed.

3. Which of the following would cause mean aortic pressure to increase?

a. Stroke volume increases from 30 to 40 mL, and heart rate decreases from 100 to 60 beats per minute.

b. Arterial compliance decreases.

c. Heart rate decreases.

d. Arterioles throughout the body dilate.

e. TPR increases.

4. The following measurements are made on a dog: heart rate, 80beats∕min; stroke volume, 30 mL; mean aortic pressure, 96 mm Hg; mean pulmonary artery pressure, 30 mm Hg; left atrial pressure, 5 mm Hg; and right atrial pressure, 12 mm Hg. TPR (taking into account both arterial and atrial pressures) is exactly:

a. 10.42 mm Hg/L/min

b. 12.50 mm Hg/L/min

c. 35.00 mm Hg/L/min

d. 37.92 mm Hg/L/min

e. 40.00 mm Hg/L/min

5. Which of the following would cause the largest decrease in coronary blood flow?

a. Coronary arterioles constrict to half their normal diameter.

b. Coronary arteries develop atherosclerosis, and lipid plaques plug up half their normal cross-sectional area.

c. Mean aortic pressure decreases to half its normal level.

d. The resistance to coronary blood flow doubles.

e. The resistance to coronary blood flow decreases to one-fourth its normal value.