In a medullated nerve fibre, the conduction of impulse is faster due to the presence of

Options

A. pericytes
B. endoneurium and epineurium
C. myelin sheath and nodes of Ranvier
D. Nissle's granules

Explanation

### Step-by-Step Solution:

1. **Understanding Medullated Nerve Fibers**:
- Medullated nerve fibers are those that are covered by a protective layer called the myelin sheath. This sheath is crucial for the proper functioning of the nerve fibers.

2. **Role of Myelin Sheath**:
- The myelin sheath acts as an insulator for the nerve fibers. It prevents the loss of electrical signals and allows for faster transmission of nerve impulses.

3. **Nodes of Ranvier**:
- Between the segments of the myelin sheath, there are small gaps known as the Nodes of Ranvier. These nodes are essential for the rapid conduction of impulses because they facilitate a process called saltatory conduction.

4. **Saltatory Conduction**:
- In saltatory conduction, the nerve impulse jumps from one Node of Ranvier to the next, rather than traveling continuously along the entire length of the fiber. This significantly increases the speed of impulse conduction.

5. **Analyzing the Options**:
- a. **Pericytes**: These are involved in the formation of the blood-brain barrier and do not contribute to impulse conduction.
- b. **Endoneurium and Epineurium**: These are protective layers around the nerve fibers but do not enhance conduction speed.
- c. **Myelin Sheath and Nodes of Ranvier**: This is the correct answer as both components are crucial for faster impulse conduction.
- d. **Nissl Granules**: These are involved in protein synthesis and do not play a role in impulse conduction.

6. **Conclusion**:
- The conduction of impulses in medullated nerve fibers is faster due to the presence of the myelin sheath and the Nodes of Ranvier. Therefore, the correct answer is option **C**: Myelin sheath and Nodes of Ranvier.