Diastolic relaxation occurs between which sounds?

Diastolic relaxation refers to the phase of the cardiac cycle where the heart muscle relaxes and the ventricles fill with blood. This process occurs following the closure of the aortic and pulmonary valves, which is represented by the second heart sound (S2). Once S2 is heard, diastolic relaxation begins, allowing the ventricles to fill with blood coming from the atria.

Looking at the choice indicating that diastolic relaxation occurs "after S2, before S1," this is correct because, during this interval, the heart enters diastole, leading to the filling of the ventricles. This is the time when the heart muscle relaxes after the contraction phase, which ends with S2 and prepares for the next contraction, which is marked by S1.

Understanding the timing of heart sounds is crucial for recognizing the phases of the cardiac cycle and the physiology of heart function, especially in conditions like heart failure where these processes may be impaired. The incorrect choices do not accurately capture the relationship between the heart sounds and the phases of diastolic relaxation.