During isovolumetric relaxation, which condition describes ventricular volume?

• A. It remains constant as all valves are closed
• B. It increases when the mitral valve opens
• C. It decreases when the aortic valve opens
• D. It remains constant as the aortic valve closes

Answer: (D)

During isovolumetric relaxation the ventricle’s volume stays the same because it relaxes without any blood entering or leaving. This happens after the aortic valve has closed and with both the aortic and mitral valves closed, so there’s no flow in or out. The phase ends when the mitral valve opens and filling begins, allowing the ventricle to regain volume. If the mitral valve opened earlier, the volume would increase; if the aortic valve opened, the ventricle would pump blood out and the volume would decrease.