Question

during atrial systole, which of the following occurs?
only 25% of the blood received by the ventricles is received.
atrioventricular valves are closed.
ventricles are in isovolumetric relaxation.
ventricular pressure decreases.

Explanation:

During atrial systole, the atria contract and pump blood into the ventricles. About 25% of the blood that fills the ventricles during the cardiac cycle comes from atrial systole. The atrioventricular valves are open to allow blood flow from atria to ventricles. The ventricles are not in isovolumetric relaxation (which occurs after ventricular systole) and ventricular pressure does not decrease during atrial systole.

Answer:

Only 25% of the blood received by the ventricles is received.