Which Event Typically Occurs at the Start of a Cardiac

Question

Which event typically occurs at the start of a cardiac cycle?
A) Ventricular blood pressure drops until reverse blood flow pushes the cusps of the semilunar valves together.
B) Atrial contraction forces a small amount of blood into the relaxed ventricles.
C) The semilunar valves open and blood is ejected.
D) Ventricular contraction pushes the atrioventricular valves closed.
E) The ventricles fully contract.

Accepted Answer

At the start of a cardiac cycle, the atria contract to force a small amount of blood into the relaxed ventricles. This is known as atrial systole and marks the beginning of the cardiac cycle.