Answer:
isovolumetric contraction is the time when heart beat cycle are all four of the heart valves closed
Step-by-step explanation:
There is a period called isovolumetric contraction during which the ventricles contract but the pulmonary and aortic valves are closed as the ventricles do not have enough force to open them. The atrioventricular valves also remain closed during the isovolumetric contraction period.