Systole and diastole are two essential processes that occur during the cardiac cycle, which is the complete sequence of events that happen during a heartbeat. These terms are used to describe the contraction and relaxation phases of the heart, respectively.
Systole refers to the contraction phase of the heart muscle. During systole, the ventricles, which are the lower chambers of the heart, contract forcefully to pump blood into the arterial circulation. This contraction is initiated by electrical signals from the heart's natural pacemaker, the sinoatrial (SA) node. As a result of systole, blood pressure within the arteries increases, allowing oxygen-rich blood to be delivered to various organs and tissues.
Diastole, on the other hand, represents the relaxation phase of the heart muscle. During diastole, the heart muscles relax to allow the chambers to refill with blood. This filling of blood occurs primarily during early diastole, known as the rapid filling phase. The atria, which are the upper chambers of the heart, also contract during diastole to facilitate blood flow into the ventricles. Diastole is crucial for the heart to replenish itself with oxygenated blood and prepare for the next cycle of systole.
In summary, systole describes the contraction phase of the heart, while diastole refers to the relaxation phase. These two distinct processes allow the heart to efficiently pump blood throughout the body during each cardiac cycle, ensuring an adequate oxygen supply to the organs and tissues.
