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 atrioventricular (AV) valves remain closed, we need to analyze each phase of the cardiac cycle:

1. **Understanding the Cardiac Cycle**: The cardiac cycle consists of four main phases:
- Atrial Systole
- Ventricular Systole
- Ventricular Diastole
- Joint Diastole

2. **Atrial Systole**: In this phase, the atria contract to push blood into the ventricles. During atrial systole, the AV valves (which include the tricuspid and mitral valves) are open to allow blood flow from the atria to the ventricles. Therefore, the AV valves are **not closed** during this phase.

3. **Ventricular Systole**: This phase involves the contraction of the ventricles. As the ventricles contract, the pressure within them increases, causing the AV valves to close. This closure prevents the backflow of blood into the atria. Thus, during ventricular systole, the AV valves are **closed**.

4. **Ventricular Diastole**: In this phase, the ventricles relax and fill with blood. The AV valves open to allow blood to flow from the atria into the ventricles. Therefore, the AV valves are **not closed** during this phase.

5. **Joint Diastole**: This phase is characterized by the relaxation of both the atria and ventricles, allowing blood to flow from the veins into the atria. During joint diastole, the AV valves are open to facilitate this blood flow. Thus, the AV valves are **not closed** during this phase.

6. **Conclusion**: After analyzing all four phases, we find that the AV valves remain closed only during **ventricular systole**.

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

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