Question

Which of the following statements are TRUE about the cardiac cycle?

A) Valves within the heart prevent the flow of blood backward.
B) EF is defined as the amount of blood ejected from the heart during diastole.
C) CO is equal to the EF times the HR.
D) Diastole is when the heart is contracting.
E) None of the above.

Answer 1

The true statement about the cardiac cycle is that valves within the heart prevent the flow of blood backward. The other statements are either partially true or incorrect regarding the definitions and timing of ejection fraction, cardiac output, and the phases of systole and diastole.

Step-by-step explanation:

The statement that is TRUE about the cardiac cycle is: A) Valves within the heart prevent the flow of blood backward. During diastole, the atrioventricular valves are open, allowing blood to flow from the atria to the ventricles without impedance. The semilunar valves are closed to prevent backflow. In contrast to statement B, EF (Ejection Fraction) is the proportion of blood that is pumped out of the ventricles with each heartbeat during systole, not diastole. As for statement C, CO (Cardiac Output) is indeed equal to the EF times the HR (Heart Rate), which represents the volume of blood ejected by the heart per minute. Lastly, statement D is incorrect because diastole is the phase when the heart relaxes and fills with blood, not contracts.