What happens during the diastole phase of the heart cycle?

During the diastole phase of the heart cycle, the heart is in a state of relaxation, allowing the chambers to fill with blood. This phase follows the contraction of the heart (systole), and during diastole, the atria and ventricles open to receive blood returning from the body and lungs.

This process is crucial for maintaining a continuous flow of blood as it ensures that there is enough volume in the heart when it enters the next phase of contraction. The atrioventricular valves (the tricuspid and mitral valves) open, allowing blood to flow from the atria into the ventricles, and the semilunar valves are closed, preventing backflow into the arteries. This filling is essential for effective circulation, as it maximizes the volume of blood pumped with each heartbeat during systole.

Thus, option C accurately describes the diastole phase as the time when the heart is refilling with blood, highlighting its critical role in the cardiac cycle.