During diastole, what occurs in the heart?

During diastole, the heart goes through a crucial phase where it relaxes and fills with blood. This phase follows the contraction of the heart muscle, known as systole, when blood is pumped out to the lungs and the rest of the body. As the heart relaxes, the chambers, specifically the atria and ventricles, expand, allowing blood to flow from the veins into the heart. This process is vital because it ensures that there is adequate blood volume for the next contraction cycle.

The filling of the heart during diastole is driven by pressure differences; as the heart chambers expand, the pressure within them decreases, which pulls blood into the atria from the superior and inferior vena cavae and from the pulmonary veins into the left atrium. This filling is essential for maintaining an efficient circulation system, ensuring that there is enough blood to supply oxygen and nutrients to the body during the next contraction. The ability of the heart to fill properly during diastole is as important as its ability to contract during systole for overall cardiac function.