The axon of a nerve cell is covered by a sheath called

Options

A. Epineurium
B. Medulla
C. Myelin sheath
D. Neurilemma

Answer

To answer the question "The axon of a nerve cell is covered by a sheath called," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components of a Nerve Cell**:
- A nerve cell, or neuron, consists of several parts, including the cell body, dendrites, and axon.

2. **Understand the Structure of the Axon**:
- The axon is a long, slender projection that conducts electrical impulses away from the neuron's cell body.

3. **Recognize the Protective Sheath**:
- The axon is often covered by a protective layer that insulates it and aids in the efficient transmission of nerve impulses.

4. **Examine the Options Provided**:
- **Epineurium**: This is a layer of connective tissue that surrounds peripheral nerves, not specifically the axon.
- **Medulla**: This refers to a part of the brain (medulla oblongata) and is not related to the axon.
- **Myelin Sheath**: This is the correct answer; it is a fatty layer that surrounds the axon, enhancing the speed of impulse transmission.
- **Neurilemma**: This refers to the outermost layer of the Schwann cells that wrap around the axon, but it is not the primary insulating layer.

5. **Conclude with the Correct Answer**:
- The axon of a nerve cell is covered by a sheath called the **myelin sheath**.

### Final Answer:
The axon of a nerve cell is covered by a sheath called the **myelin sheath**.

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