Cardiac Cycle in Physiology: Phases of Systole and Diastole in Human Heart Function

Описание: The cardiac cycle refers to the sequence of events that occur in the heart during one complete heartbeat. It includes alternating periods of contraction (systole) and relaxation (diastole), ensuring efficient pumping of blood throughout the body.
The cardiac cycle has three main phases:
Atrial Systole – The atria contract, pushing blood into the ventricles through the atrioventricular (AV) valves.
Ventricular Systole – The ventricles contract, increasing pressure inside them. This closes the AV valves (producing the first heart sound, lub) and opens the semilunar valves, allowing blood to be pumped into the aorta and pulmonary artery.
Complete Cardiac Diastole – Both atria and ventricles relax. Semilunar valves close (producing the second heart sound, dub), and the heart chambers refill with blood.
A normal cardiac cycle lasts about 0.8 seconds at a heart rate of 75 beats per minute. Proper coordination of electrical activity and muscle contraction ensures effective circulation and maintenance of blood pressure.
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