Function of T-tubules in muscles is to

Options

A. secrete acetylcholine
B. conduct impulses
C. support and muscle fibres
D. store calcium

Answer

**Step-by-Step Solution:**

1. **Understanding T-tubules**: T-tubules, also known as transverse tubules, are invaginations of the sarcolemma (muscle cell membrane) that penetrate into the interior of muscle fibers (myocytes).

2. **Structure and Function**: These tubules form a highly branched and interconnected network that connects with the sarcoplasmic reticulum, which is crucial for muscle contraction.

3. **Role in Muscle Contraction**: The primary function of T-tubules is to facilitate the rapid transmission of action potentials (electrical impulses) from the surface of the sarcolemma into the muscle cell. This allows for synchronized contraction of the muscle fibers.

4. **Calcium Regulation**: T-tubules also play an important role in regulating calcium concentration within the muscle cell, which is essential for muscle contraction.

5. **Evaluating the Options**:
- **Option A (secrete acetylcholine)**: This is incorrect because acetylcholine is secreted by cholinergic neurons, not T-tubules.
- **Option B (conduct impulses)**: This is correct as T-tubules conduct impulses into the muscle cells, facilitating contraction.
- **Option C (support muscle fibers)**: This is incorrect; T-tubules do not primarily support muscle fibers.
- **Option D (store calcium)**: This is incorrect; calcium is stored in the sarcoplasmic reticulum, not in T-tubules.

6. **Conclusion**: The correct answer is **Option B: conduct impulses**.