Question

Explain the steps of the cardiac cycle.

Answer 1

• Atrial Systole: The atria contract simultaneously and push the deoxygenated and oxygenated blood into the respective ventricles through the open tricuspid and mitral valves. During this phase, the semilunar valves remain firmly closed.
• Ventricular Systole: The ventricles contract powerfully, causing the atrioventricular (tricuspid and mitral) valves to snap shut, which produces the first heart sound called "lubb". The high pressure forces the semilunar valves to open, pumping blood into the pulmonary artery and the aorta.
• Ventricular Diastole: The ventricles relax, causing the blood pressure inside them to drop quickly. This results in the sudden closure of the semilunar valves, which produces the second heart sound called "dupp", while blood returning through the venae cavae and pulmonary veins refills the chambers.
• Rhythmic Repetition: The entire sequence of events repeats rhythmically for every individual heartbeat, where the various valves continuously operate to ensure the strictly one-way flow of blood throughout the cycle.