What is the order of the cardiac cycle beginning with the atria in diastole?

In the cardiac cycle, starting with the atria in diastole means that the atria are filling with blood as they relax. The cycle progresses as follows: during atrial diastole, blood flows from the veins into the atria. Once the atria are sufficiently filled, they contract (begin systole) to push blood into the ventricles.

Following the contraction of the atria, the ventricles are filled with blood and then enter a phase called isovolumetric contraction, during which the ventricles contract without changing volume—this prepares them for ejection of blood. The blood is then ejected from the ventricles into the arteries during ventricular systole.

The correct sequence begins with the atria in diastole, followed by atrial systole as they eject blood into the ventricles, and then ventricle systole as they contract and eject blood. The option accurately captures this progression of events, highlighting the relations between atrial and ventricular activities in the cycle.

In summary, the chosen answer aligns with the proper sequence of cardiac events, accurately reflecting the physiological processes involved in each phase of the cardiac cycle.