What is the medical term for the heart's relaxation phase?

The heart's relaxation phase is referred to as the diastolic phase. During this phase, the heart muscle relaxes after contraction (systole), allowing the chambers of the heart, particularly the ventricles, to fill with blood from the atria. This process is essential for maintaining an adequate blood supply to the body, as it directly influences the amount of blood that will be pumped out during the next contraction.

In the context of this question, understanding the diastolic phase is crucial because it is when the heart is in a resting state, preparing for the next cycle of beating. This phase ensures that there is sufficient blood volume in the heart for effective circulation.

The cardiac cycle refers more generally to the sequence of events during one heartbeat, including both phases of contraction (systole) and relaxation (diastole). Isovolumetric contraction is a specific part of the cardiac cycle that occurs during systole, not diastole, when the heart muscle contracts but the volume of blood within the ventricles remains unchanged as the valves are closed. Prolonged systole describes an extended contraction phase and does not correspond to relaxation at all.