Isovolumic contraction is defined as?

Isovolumic contraction is defined as?

• A. A phase where ventricular pressure increases, AV valves close, but blood volume remains the same.
• B. A phase where ventricular pressure decreases and the SL valves open.
• C. A phase where atria contract and fill the ventricles.
• D. A phase where both sets of valves open and blood rapidly flows.

Answer: (A)

Isovolumic contraction occurs when the ventricles begin to contract but all heart valves are momentarily closed, so no blood is ejected. As the ventricular muscle contracts, the pressure inside the ventricle rises quickly, causing the atrioventricular valves to snap shut to prevent backflow into the atria. The semilunar valves remain closed because the ventricular pressure has not yet exceeded the pressure in the aorta and pulmonary artery. With both sets of valves closed, the ventricular volume stays constant despite ongoing contraction. This phase ends when the ventricular pressure becomes high enough to open the semilunar valves and blood starts to be ejected.

Isovolumic contraction occurs when the ventricles begin to contract but all heart valves are momentarily closed, so no blood is ejected. As the ventricular muscle contracts, the pressure inside the ventricle rises quickly, causing the atrioventricular valves to snap shut to prevent backflow into the atria. The semilunar valves remain closed because the ventricular pressure has not yet exceeded the pressure in the aorta and pulmonary artery. With both sets of valves closed, the ventricular volume stays constant despite ongoing contraction. This phase ends when the ventricular pressure becomes high enough to open the semilunar valves and blood starts to be ejected.