Which point on the diagram marks the beginning of ventricular systole?

Ans. A. APressure - volume loop of the left ventricle. During diastole, the ventricle fills and pressure increases from d to a. Pressure then rises sharply from a to b during isovolumetric contraction and from b to c during ventricular ejection. At c, the aortic valves close and pressure falls during isovolumetric relaxation from c back to d.Isovolumetric contraction starts at A therefore it is the beginning of ventricular systole.