Cardiac cycle is defined as the complete cycle of events in the heart from the beginning of one heart beat to the beginning of the next.
The three stages of Cardiac Cycle are –
- Atrial systole
- Ventricular Systole
- Complete Cardiac Diastole.
During each Cardiac cycle, deoxygenated blood is forced through the right side of the heart to the lungs, while oxygenated blood is forced through the left side of the heart to the rest of the body.
The Cardiac cycle has 3 stages:
- Atrial systole– When the muscles of the heart relax, the atria (the upper chambers) fill with blood from the vena cava and pulmonary vein. The semilunar valves shut, preventing blood from flowing into the ventricles.
- Ventricular Systole- When the atria contract, blood is forced through the tricuspid and bicuspid valves into the ventricles (the lower chambers).
- Complete Cardiac Diastole- The ventricles contract and the semilunar valves open as blood surges out of the heart through the pulmonary artery and aorta. At the same time, the bicuspid and tricuspid valves shut.