Südametsükliks

Südametsükliks, often translated as cardiac cycle, refers to the complete sequence of events that occurs during one heartbeat. It is the fundamental process by which the heart pumps blood throughout the body. The cardiac cycle consists of two main phases: diastole and systole.

Diastole is the relaxation phase of the heart muscle. During diastole, the atria and ventricles of the heart relax, allowing them to fill with blood. This filling occurs passively at first, and then more actively as the atria contract to push the remaining blood into the ventricles.

Systole is the contraction phase of the heart muscle. Following diastole, the ventricles contract forcefully, ejecting the blood from the heart into the pulmonary artery (from the right ventricle) and the aorta (from the left ventricle). Simultaneously, the atria are relaxing and beginning to refill with blood.

These two phases, diastole and systole, occur in a coordinated manner, regulated by the heart's electrical conduction system. The characteristic sounds of a heartbeat, often described as "lub-dub," are produced by the closing of the heart valves during these cycles. The "lub" sound is caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular systole, and the "dub" sound is produced by the closure of the semilunar valves (aortic and pulmonary) at the end of ventricular systole. The continuous repetition of the cardiac cycle ensures the uninterrupted circulation of blood.