NEET BIOLOGY

Detailed explanation-1: -It is a period of contractions of the ventricles present in a heart during the cardiac cycle . The increased ventricular pressure during ventricular systole causes closure of the bicuspid & tricuspid valves to avoid the backflow of blood into the atria.

Detailed explanation-2: -Semilunar valves are open during ventricular systole, forcing the blood to flow into the pulmonary artery. Bicuspid and tricuspid valves get closed at the beginning of ventricular systole.

Detailed explanation-3: -As the blood fills the chamber the atria contract to push the blood through the valves, and this is known as the atrial systole. It only at this stage does the bicuspid and tricuspid valve open.

Detailed explanation-4: -Due to contraction of the ventricles (ventricular systole), the pressure inside the ventricles rises that forces to open the semilunar valves of aorta and pulmonary artery so that the blood enters into these vessels.

Detailed explanation-5: -So during atrial systole, the bicuspid and tricuspid valves are open, and the pulmonary/aortic semilunar valves are closed. Then during the diastole, the bicuspid and tricuspid valves are closed.