Isovolumetric systole is duration between

Options

A. Closure of AV valve and semilunar valve
B. Closure of semilunar valve and opening of AV valve
C. Closure of tricuspid and closure of bicuspid valve
D. Closure of tricuspid and opening of bicuspid valve

Answer

To solve the question regarding the duration of isovolumetric systole, we need to understand the cardiac cycle and the specific events that occur during this phase.

### Step-by-Step Solution:

1. **Understanding Isovolumetric Systole**:
- Isovolumetric systole is a phase of the cardiac cycle. The term "isovolumetric" refers to a period where the volume of blood in the ventricles remains constant, despite the contraction of the heart muscle.

2. **Timing of Isovolumetric Systole**:
- This phase occurs during early systole, specifically after the closure of the atrioventricular (AV) valves and before the opening of the semilunar valves.

3. **Closure of Valves**:
- The AV valves (which include the tricuspid and bicuspid (mitral) valves) close first when the ventricles begin to contract. This prevents backflow into the atria.
- Following this, the ventricles continue to contract, but the semilunar valves (pulmonary and aortic valves) have not yet opened, leading to no change in volume.

4. **Conclusion**:
- Therefore, the duration of isovolumetric systole is between the closure of the AV valves and the opening of the semilunar valves.

### Final Answer:
Isovolumetric systole is the duration between the closure of the AV valve and the opening of the semilunar valve.

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