Which of the following best represents the cardiac cycle?

The cardiac cycle encompasses the complete sequence of events that occur in the heart during a single heartbeat, which includes both the contraction and relaxation phases associated with the pumping of blood. Option B accurately describes this cycle as the duration from one heartbeat to the next, capturing the entire process that includes atrial contraction, ventricular contraction, and the relaxation phases for both.

Understanding the cardiac cycle is essential, as it not only involves the mechanical actions of the heart but also the timing of electrical impulses that initiate these actions. The cardiac cycle is critical for maintaining effective blood circulation throughout the body, highlighting the importance of coordinating muscle contractions and relaxations.

The other options are narrow in focus and do not encompass the entire cardiac cycle. The relaxation phase of the heart, while a component of the cycle, is just one part of the overall sequence. Contraction of the atria only mentions one phase without considering the vital participation of the ventricles or the relaxation phase that follows. Similarly, while the electrical activity in the ventricles occurs during the cardiac cycle, it does not reflect the complete time frame from one heartbeat to the next, as it ignores the entire sequence of events including atrial contraction and relaxation phases. This makes option B the most comprehensive and representative description of the cardiac