What defines a cardiac cycle?

The cardiac cycle is defined as the sequence of events that occurs during one complete heartbeat, encompassing all phases of heart activity, including both contraction and relaxation. This cycle includes the time from the end of one ventricular contraction, known as systole, to the end of the next ventricular contraction, which involves a period of relaxation known as diastole. This definition captures the comprehensive function of the heart, where the phases of contraction and relaxation coordinate to effectively pump blood throughout the body.

The choice relates specifically to the mechanics of the ventricles, which are the chambers responsible for pumping blood out of the heart. Understanding the entire cardiac cycle is crucial in assessing the efficiency of the heart and overall cardiovascular health because successful circulation relies on the proper timing and function of these cycles.

The other definitions, while they touch on aspects of heart function, do not encapsulate the full scope of what happens during the entire cardiac cycle. For instance, defining it solely as the period from one heartbeat to the next does not address the intricate processes occurring within the heart during contraction and relaxation. Similarly, focusing only on the atrial contraction neglects the vital role of ventricular contraction, while referencing the time it takes for blood to flow through the body extends beyond the scope of just the