what is caraidic cycle. Describe the events that occour during different phases of caraidic cycle
Answers
The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, followed by a period of robust contraction and pumping of blood, dubbed systole.
First Diastole Period:-
During the first diastole period, the atriaand ventricles are relaxed and the atrioventricular valves are open. Oxygen-depleted blood returning to the heart from the body passes through the superior and inferior vena cavae and flows to the right atrium. The open atrioventricular valves (tricuspid and mitral valves) allow blood to pass through the atria to the ventricles. Impulses from the sinoatrial (SA) node travel to the atrioventricular (AV) node and the AV node send signals that trigger both atria to contract. As a result of the contraction, the right atrium empties its contents into the right ventricle. The tricuspid valve, located between the right atrium and right ventricle, prevents blood from flowing back into the right atrium.
First Diastole Period:-
At the beginning of the first systole period, the right ventricle is filled with blood passed on from the right atrium. The ventricles receive impulses from fiber branches (Purkinje fibers), which carry electrical impulses to the ventricles causing them to contract. As this occurs, the atrioventricular valves close and the semilunar valves (pulmonary and aortic valves) open. Ventricular contraction causes oxygen-depleted blood from the right ventricle to be pumped to the pulmonary artery. The pulmonary valve prevents blood from flowing back into the right ventricle. The pulmonary artery carries oxygen-depleted blood along the pulmonary circuit to the lungs. There, blood picks up oxygen and is returned to the left atrium of the heart by the pulmonary veins.
2nd Diastole Period :-
In the second diastole period, the semilunar valves close and the atrioventricular valves open. Oxygenated blood from the pulmonary veins fills the left atrium (blood from the venae cavae is also filling the right atrium at this time). The SA node contracts again triggering both atria to contract. Atrial contraction causes the left atrium to empty its contents into the left ventricle (the right atrium is also emptying blood into the right ventricle at this time). The mitral valve, located between the left atrium and left ventricle, prevents oxygenated blood from flowing back into the left atrium.
2nd Systole Period:-
During the second systole period, the atrioventricular valves close and the semilunar valves open. The ventricles receive impulses and contract. Oxygenated blood in the left ventricle is pumped to the aorta and the aortic valve prevents the oxygenated blood from flowing back into the left ventricle (oxygen-depleted blood is also being pumped from the right ventricle to the pulmonary artery at this time). The aorta branches out to provide oxygenated blood to all parts of the body through systemic circulation. After its tour through the body, oxygen-depleted blood is returned to the heart via the venae cavae.
