Working of Human Heart
Working of Human Heart
The cyclic events occur in each heartbeat together is called a cardiac cycle. which completes in about 0.8 seconds and includes the following events.
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Auricular Systole
The right auricle receives deoxygenates blood from the body through openings of vena cavae. while left auricle received oxygenated blood from the lungs, through four pulmonary veins. The flow of blood in right auricle stimulates the SA node which generates impulse of the first contraction. This impulse is spread out over the walls of both the auricles as a wave of contraction.
As a result, the auricles contract simultaneously and push the blood into the respective ventricles through AV apertures. The auricular systole lasts for 0.1 seconds.
Ventricular systole
During ventricular systole deoxygenated blood from the right ventricle is pumped into lungs for oxygenation while oxygenated blood from the left ventricle is pumped into the systemic aorta which districts the blood to all parts of the body. Contraction of the left ventricle is stronger than the contraction of the right ventricle. Ventricular contraction is brought about by AV node, Bundle of His and Purkinje fibres. ventricular systole lasts for 0.3 seconds.
Joint diastole
During joint diastole both the auricles and ventricles undergoes relaxation hence also called as complete cardiac. During diastole backflow of the blood from the aorta into ventricles is prevented by the closing of semilunar Valves. During this phase, auricles get filled with respective blood and the new cardiac cycle begins. The joint diastole lasts for about 0.4 seconds.
