szívösszehúzódás

Szívösszehúzódás, also known as cardiac contraction or systole, is the fundamental mechanical process by which the heart pumps blood throughout the body. This rhythmic process involves the coordinated contraction of the heart's muscular walls, primarily the ventricles, which are the lower chambers responsible for ejecting blood into the pulmonary artery and the aorta.

The cardiac cycle is divided into two main phases: systole and diastole. Systole is the contraction phase, during which the heart muscle shortens and thickens, reducing the volume of the heart chambers and forcing blood out. Diastole, conversely, is the relaxation phase, where the heart chambers refill with blood.

During ventricular systole, the electrical impulse originating from the sinoatrial (SA) node travels through the heart, triggering the depolarization of the cardiac muscle cells. This electrical activity leads to a rapid influx of calcium ions, initiating the contractile machinery of the muscle. The increased pressure within the ventricles forces the semilunar valves (aortic and pulmonary valves) open, allowing blood to flow into the respective arteries. Simultaneously, the atrioventricular valves (mitral and tricuspid valves) close, preventing the backflow of blood into the atria.

The strength and duration of szívösszehúzódás are crucial for maintaining adequate blood circulation. Factors such as heart rate, preload (the volume of blood in the ventricles before contraction), afterload (the resistance the heart must overcome to eject blood), and the intrinsic contractility of the myocardium all influence the efficiency of this process. Disruptions in szívösszehúzódás can lead to various cardiovascular conditions, including heart failure.