What occurs during the diastole of the heart?

During diastole, the heart is in a phase of relaxation and filling with blood. This phase comprises two primary components: the passive filling of the ventricles and the active filling from the atria. Specifically, as the ventricles relax, blood flows from the atria into the ventricles due to the pressure gradient, filling the ventricles with blood.

In this context, while the atria also undergo a filling process (with blood returning from the body and lungs), the hallmark feature of diastole is that the ventricles are filling with blood as they prepare for the next contraction. Thus, the description that the atria are emptying and the ventricles are filling accurately reflects what happens during this phase of the cardiac cycle.

Other choices describe actions that do not align with the physiological processes occurring during diastole. Hence, the correct understanding of diastolic function is crucial for interpreting cardiac mechanics and assessing cardiovascular health.