In a cardiac cycle, the interval is shorter between

Options

A. lubb and dup sounds
B. dup and lub sounds
C. lubb and lubb sounds
D. dup and dup sounds

Answer

To solve the question regarding the intervals in a cardiac cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cardiac Cycle**: The cardiac cycle consists of a series of events that occur during one heartbeat. It includes the contraction (systole) and relaxation (diastole) of the heart chambers.

2. **Identify Heart Sounds**: There are four heart sounds produced during the cardiac cycle, but typically only two are heard clearly:
- **First Heart Sound (S1)**: Known as "lub," produced by the closure of the atrioventricular (AV) valves (mitral and tricuspid valves).
- **Second Heart Sound (S2)**: Known as "dub," produced by the closure of the semilunar valves (aortic and pulmonary valves).

3. **Determine the Intervals**: The intervals between these heart sounds are crucial for understanding the timing of the cardiac cycle:
- The interval between the first heart sound (S1) and the second heart sound (S2) is approximately **0.3 seconds**.
- The interval between the second heart sound (S2) and the first heart sound (S1) is approximately **0.5 seconds**.

4. **Compare the Intervals**: Since the question asks for the interval that is shorter, we compare the two intervals:
- **S1 to S2**: 0.3 seconds (shorter interval)
- **S2 to S1**: 0.5 seconds (longer interval)

5. **Conclusion**: The interval that is shorter is between the first heart sound (S1) and the second heart sound (S2), which is 0.3 seconds.

### Final Answer:
The interval is shorter between the first heart sound (S1) and the second heart sound (S2).

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