During the cardiac cycle the opening of the aortic valve takes place at the: (A) Beginning of systole, (B) End of isovolumetric contraction, (C) End of diastole, (D) End of diastasis
Answer is B. Ans. (b) End of isovolumetric contractionRef: Ganong, 25th ed/p.540Isovolumetric contraction#To eject blood into aorta and pulmonary artery, ventricles must open aortic and pulmonary valve#The sole purpose of this phase is to open these valves#The ventricle contracts against the closed valves (both AV valves and semilunar valves are closed)#This means that ventricular blood volume won't change (isovolumetric) but the pressure generated by the ventricle tremendously rises.#Once the pressure rises above 80 mm Hg, aortic valve opens. Similar changes also happen in right ventricle which opens the pulmonary valve