What defines the 'diastolic' phase in the cardiac cycle?

The 'diastolic' phase in the cardiac cycle is defined as the relaxation stage of the heart. During this phase, the heart muscle relaxes after contraction, allowing the chambers of the heart, specifically the atria and ventricles, to fill with blood. This is crucial for maintaining an effective and consistent flow of blood throughout the body.

When the heart is in diastole, the pressure within the heart chambers decreases, which facilitates the inflow of blood from the veins; the atria fill with blood from the body, and the ventricles receive blood from the atria. This phase is vital for proper cardiac function because it sets the stage for the next phase, which is the contraction (systole), where the heart pumps the blood out to the lungs and the rest of the body.

Understanding this distinction helps clarify the role of the diastolic phase in the overall cardiac cycle and the importance of both contraction and relaxation for effective heart function.