Chapter 2, Problem 77PP

BIO Blood flow in the heart. The human circulatory system is closed—that is, the blood pumped out of the left ventricle of the heart into the arteries is constrained to a series of continuous, branching vessels as it passes through the capillaries and then into the veins as it returns to the heart. The blood in each of the heart’s four chambers comes briefly to rest before it is ejected by contraction of the heart muscle.

77. The velocity of blood in the aorta can be measured directly by using ultrasound techniques. A typical graph of blood velocity as a function of time during a single heartbeat is shown in Figure 2.56. Which of the following is the best interpretation of this graph?

1. A.    The blood flow changes direction at about 0.25 s.
2. B.     The speed of blood flow begins to decrease at about 0.10 s.
3. C.     The acceleration of the blood is greatest in magnitude at about 0.25 s.
4. D.    The acceleration of the blood is greatest in magnitude at about 0.10 s.

Figure 2.56

Problem 77