What does diastole refer to in the cardiac cycle?

Diastole refers to the phase in the cardiac cycle where the heart muscles relax and the chambers of the heart fill with blood. During diastole, the heart returns to its resting state after contraction, which allows blood to flow into the atria from the veins; this process is crucial for ensuring that the heart has enough blood to pump out during the next contraction.

The key aspects of diastole are both the relaxation of the heart muscles and the filling of the chambers with blood, which is why choosing an answer that covers both elements is critical to understanding the complete function of this phase. The relaxation of the heart occurs after the previous contraction (systole), creating a moment of reduced pressure in the heart that facilitates the inflow of blood.

Understanding diastole encompasses recognizing that it serves not only as the period of muscle relaxation but also as a necessary prelude to the subsequent contraction, thereby playing a fundamental role in the efficiency and effectiveness of the heart’s pumping action.