A firm hold for the filaments in a sarcomere is provided by

Options

A. M-line
B. Z-line
C. Triad system
D. peripheral parts of the H-zone

Answer

**Step-by-Step Solution:**

1. **Understanding Sarcomere Structure**: The sarcomere is the basic structural unit of muscle fibers. It is composed of thick and thin filaments that are responsible for muscle contraction.

2. **Identifying Filaments**: The thick filaments are primarily made up of myosin, while the thin filaments are made up of actin. These filaments slide past each other during muscle contraction.

3. **Role of M-line**: The M-line is a structure located in the center of the sarcomere. It serves as an anchoring point for the thick filaments (myosin). The M-line helps to maintain the alignment and organization of the filaments within the sarcomere.

4. **Other Structures**: The Z-line marks the boundary of each sarcomere and connects to the thin filaments (actin). The I-band contains only thin filaments, while the A-band contains both thick and thin filaments.

5. **Conclusion**: The M-line provides a firm hold for the thick filaments in the sarcomere, ensuring the structural integrity and proper functioning of the muscle during contraction.

**Final Answer**: A firm hold for the filaments in a sarcomere is provided by the M-line.

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