Which statement accurately describes diastole?

Diastole is the phase of the cardiac cycle when the heart muscle relaxes, allowing the chambers to fill with blood. During this period, both the atria and ventricles are in a state of relaxation, which is crucial for ensuring that the heart receives an adequate volume of blood to pump out during the subsequent contraction (systole). This phase occurs after the ventricles have emptied their blood into the aorta and pulmonary artery, transitioning smoothly to a state where blood flows from the veins into the atria, and then into the ventricles.

As the heart relaxes, the atrioventricular (AV) valves open, permitting blood to flow from the atria into the ventricles, highlighting the importance of this filling phase for maintaining effective cardiovascular function. This process is vital for optimal heart performance, as sufficient filling during diastole is necessary to ensure adequate stroke volume during systole.

The other statements describe different aspects or phases of heart function. The first option refers to systole, where the ventricles contract, and this is not related to diastole. The closure of valves to prevent backflow typically happens during systole when the heart contracts. Additionally, while the aortic and pulmonic valves do indeed close at