Question

Explain cardiac cycle stepwise?

Answer 1

Hint: The cardiac cycle is the performance of the human heart from ending to the beginning of one heartbeat. It mainly consists of two phases: one during which the heart muscle relaxes and refills with blood following the pumping of blood in the second phase. The relaxation and contraction of heart’s atria and ventricles approximately lasts for 0.8 seconds

Complete answer:
The cardiac cycle has two phases namely, diastole and the systole.
The diastole is the phase in which blood returns to the heart from the superior and inferior Vena cava and flows it into the right atrium. The pressure in the right atrium increases due to the inflow of a large amount of blood and it also increases the pressure of the right ventricle.
As a result, the tricuspid valve opens and allows the blood to flow into the right ventricle. The oxygenated blood coming from the lungs flows into the left atrium and due to which left atrial pressure increases, the mitral valve also opens and blood flows into the left ventricle.
In the systole phase, blood flows from the pair of atria into their respective ventricles. The blood flow occurs as result of contraction of the atrial muscle due to the depolarization of the atria.
The semilunar valves open when the ventricular muscle contracts and generates pressure in the ventricle. When the heart muscle relaxes again the diastole phase begins.

Note: Isovolumetric contraction is the period occurs during cardiac cycle in which the ventricles contract but the pulmonary and aortic valves are closed as the ventricles do not hold enough force. A cardiac cycle is a complete heartbeat. It consists of two familiar sounds known as “lub” and “dub” sound. It is the sound produced during opening and closing of valves.