Hjärtsammandragning

Hjärtsammandragning, also known as cardiac contraction or systole, is the fundamental process by which the heart muscle contracts to pump blood throughout the body. This rhythmic contraction is essential for maintaining circulation and delivering oxygen and nutrients to all tissues. The process begins in the sinoatrial node, a specialized group of cells in the right atrium, which generates an electrical impulse. This impulse spreads across the atria, causing them to contract and push blood into the ventricles.

Following atrial contraction, the impulse travels to the atrioventricular node, where it is briefly delayed. This delay allows the ventricles to fill completely with blood. The impulse then rapidly conducts through the bundle of His and Purkinje fibers, stimulating the ventricular muscle to contract forcefully. This ventricular contraction, or systole, ejects blood from the ventricles into the pulmonary artery (from the right ventricle to the lungs) and the aorta (from the left ventricle to the rest of the body).

The relaxation phase of the heart, known as diastole, follows systole. During diastole, the heart muscle relaxes, allowing the chambers to refill with blood in preparation for the next contraction. The coordinated sequence of contraction and relaxation ensures efficient blood flow and is regulated by the nervous system and hormones. Any disruption to this intricate process can lead to various cardiovascular conditions.