The medullary sheath of the nerve fibre is interrupted at intervals by

Options

A. septa
B. node of Ranvier
C. synapses
D. glia

Answer

### Step-by-Step Solution:

1. **Understanding the Medullary Sheath**: The medullary sheath, also known as the myelin sheath, is a protective covering that surrounds the axons of many neurons. It plays a crucial role in the conduction of nerve impulses.

2. **Identifying Interruptions**: The question asks what interrupts the medullary sheath at intervals. This interruption is essential for the proper functioning of nerve impulses.

3. **Recognizing the Interruption Points**: The interruptions in the myelin sheath occur at specific points along the axon. These points are known as the Nodes of Ranvier.

4. **Function of Nodes of Ranvier**: The Nodes of Ranvier facilitate the rapid conduction of nerve impulses. When an action potential occurs, it can jump from one node to the next, a process known as saltatory conduction. This allows for faster transmission of signals along the axon.

5. **Conclusion**: Therefore, the medullary sheath of the nerve fiber is interrupted at intervals by the Nodes of Ranvier.

### Final Answer:
The medullary sheath of the nerve fiber is interrupted at intervals by the **Nodes of Ranvier**.

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