At rest, when muscle is relaxed, thin filaments interdigitate with thick filaments only

Options

A. Outside A- band
B. Outside H- band
C. Inside A- band
D. Inside M-line

Answer

To answer the question regarding the position of thin filaments interdigitating with thick filaments when the muscle is at rest and relaxed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Muscle Structure**:
- Muscles are made up of myofibrils, which contain thick (myosin) and thin (actin) filaments. The arrangement of these filaments is crucial for muscle contraction and relaxation.

2. **Identifying Key Bands**:
- The A band is the region where thick filaments (myosin) are present, and it also includes the overlapping area with thin filaments (actin).
- The H zone (or H band) is the central part of the A band where there are only thick filaments and no overlapping thin filaments.

3. **Analyzing the Relaxed State**:
- When the muscle is relaxed, the thin filaments do not overlap significantly with the thick filaments. The overlap occurs primarily outside the H zone.
- In the relaxed state, the thin filaments extend into the A band but do not reach the center (H zone) where only thick filaments are present.

4. **Determining the Overlap Location**:
- Since the thin filaments interdigitate with the thick filaments outside the H zone, we can conclude that the correct answer to the question is that the thin filaments overlap with the thick filaments outside the H band.

5. **Choosing the Correct Option**:
- Based on the analysis, the correct answer is **Option B: outside H band**.

### Final Answer:
The thin filaments interdigitate with thick filaments **outside the H band** when the muscle is at rest and relaxed.

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