What event immediately follows the closure of the atrioventricular valves and coincides with the onset of ventricular systole?

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

Answer: (A)

Verified step by step guidance

1. Understand the cardiac cycle phases: The cardiac cycle consists of diastole (relaxation) and systole (contraction) phases for both atria and ventricles.
2. Identify the role of atrioventricular (AV) valves: These valves prevent backflow of blood from the ventricles to the atria during ventricular contraction.
3. Recognize the sequence of events: The closure of the AV valves marks the end of atrial systole and the beginning of ventricular systole.
4. Define isovolumetric contraction: This is the phase in ventricular systole where the ventricles contract with no volume change because all heart valves are closed.
5. Connect the closure of AV valves to isovolumetric contraction: The closure of the AV valves immediately precedes isovolumetric contraction, as the ventricles begin to contract but have not yet ejected blood.