Atrial Systole occurs during which part of the cardiac cycle?

Atrial Systole refers specifically to the phase in the cardiac cycle when the atria contract, actively pushing blood into the ventricles. This contraction occurs just before the ventricles begin to contract, following ventricular diastole, where the ventricles are filled with blood. During atrial systole, the atria are in a state of contraction, allowing for the final filling of the ventricles before they themselves enter ventricular systole. Thus, the timing of atrial systole is crucial as it enables efficient blood flow and proper sequencing of the heart’s pumping action.

In the context of the choices presented, atrial systole distinctly identifies the phase during which the atria contract, making that the accurate answer. Other phases of the cardiac cycle, such as ventricular systole and diastole, describe the states of the ventricles rather than the atria, while “complete cardiac cycle” refers to the entirety of the heart's rhythmic activity, rather than pinpointing the specific timing of atrial systole.