During which of the following of the following events of cardiac cycle, AV valves remain closed?

Options

A. Atrial systole
B. Ventricular systole
C. Ventricular diastole
D. Joint diastole

Answer

To determine during which event of the cardiac cycle the AV (atrioventricular) valves remain closed, we need to analyze the different phases of the cardiac cycle:

1. **Understanding AV Valves**: The AV valves consist of the mitral valve (between the left atrium and left ventricle) and the tricuspid valve (between the right atrium and right ventricle). Their primary function is to prevent the backflow of blood from the ventricles into the atria during ventricular contraction.

2. **Phases of the Cardiac Cycle**:
- **Atrial Systole**: This phase occurs when the atria contract, pushing blood into the ventricles. During this time, the AV valves are open to allow blood flow from the atria to the ventricles.
- **Ventricular Systole**: In this phase, the ventricles contract. As the ventricles contract, the pressure increases, causing the AV valves to close to prevent backflow of blood into the atria. This is the key phase where the AV valves remain closed.
- **Ventricular Diastole**: This is the relaxation phase of the ventricles. During this time, the AV valves open to allow blood to flow from the atria into the ventricles.
- **Joint Diastole**: This is a brief phase where all chambers of the heart are relaxed, and all valves are open, allowing blood to fill the heart.

3. **Conclusion**: The AV valves remain closed during **ventricular systole** when the ventricles contract and push blood into the aorta and pulmonary trunk.

**Final Answer**: The AV valves remain closed during **ventricular systole**.

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