During which phase are the ventricles relaxed with all valves closed?

During which phase are the ventricles relaxed with all valves closed?

• A. Isovolumetric relaxation
• B. Atrial systole
• C. Ventricular ejection
• D. Isovolumetric contraction

Answer: (A)

In the heart, there is a brief period in the diastolic phase when the ventricles are relaxing and no blood is moving because every valve is closed. This is when the semilunar valves have just shut and the AV valves are still closed as the ventricular pressure falls. With all valves closed, the ventricular volume stays the same while the muscle fibers lengthen as they relax. This is the isovolumetric relaxation phase. It ends when the ventricular pressure drops below the atrial pressure and the AV valves open, allowing rapid filling of the ventricles.

In the heart, there is a brief period in the diastolic phase when the ventricles are relaxing and no blood is moving because every valve is closed. This is when the semilunar valves have just shut and the AV valves are still closed as the ventricular pressure falls. With all valves closed, the ventricular volume stays the same while the muscle fibers lengthen as they relax. This is the isovolumetric relaxation phase. It ends when the ventricular pressure drops below the atrial pressure and the AV valves open, allowing rapid filling of the ventricles.