The surface of nerve fibres bear narrow areas called

Options

A. Schwann cells
B. Schwann nodes
C. Nissl granules
D. Nodes of Ranvier.

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks about the narrow areas on the surface of nerve fibers. We need to identify the correct term that describes these areas.

2. **Analyzing the Options**: The options provided are:
- Schwann cells
- Schwann nodes
- Basal granules
- Nodes of Ranvier

3. **Identifying the Correct Option**:
- **Schwann Cells**: These are glial cells that form the myelin sheath around peripheral nerve fibers but are not the narrow areas themselves.
- **Schwann Nodes**: This term is not commonly used in the context of nerve fibers.
- **Basal Granules**: These are not related to the structure of nerve fibers; they are associated with ribosomes in neurons.
- **Nodes of Ranvier**: These are the correct answer. They are the periodic gaps in the myelin sheath surrounding the axon of a neuron.

4. **Explaining Nodes of Ranvier**: Nodes of Ranvier are crucial for the conduction of nerve impulses. They expose the cell membrane of the axon, allowing for the rapid movement of ions in and out of the neuron, which is essential for the propagation of action potentials.

5. **Conclusion**: The correct answer to the question is "Nodes of Ranvier".

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