Which of the following is a purely motor nerve?

Options

A. Vagus
B. Facial
C. Abducens
D. Trigeminal

Answer

To determine which of the following is a purely motor nerve, we need to analyze each option provided:

1. **Vagus Nerve**: The vagus nerve is a mixed nerve, meaning it carries both sensory and motor fibers. It is involved in various functions, including heart rate, gastrointestinal peristalsis, and sweating.

2. **Facial Nerve**: The facial nerve is also a mixed nerve. It carries motor fibers that control the muscles of facial expression, but it also has sensory fibers for taste from the anterior two-thirds of the tongue.

3. **Abducens Nerve**: The abducens nerve is a purely motor nerve. It is responsible for innervating the lateral rectus muscle of the eye, which is involved in eye movement.

4. **Trigeminal Nerve**: The trigeminal nerve is another mixed nerve. It has sensory functions for the face and motor functions for the muscles of mastication (chewing).

Based on this analysis, the answer to the question is:

**The purely motor nerve among the options is the Abducens Nerve.**

### Step-by-Step Solution:
1. **Identify the Nerves**: List the nerves provided in the options: Vagus, Facial, Abducens, and Trigeminal.
2. **Classify Each Nerve**:
- Vagus: Mixed (sensory and motor)
- Facial: Mixed (sensory and motor)
- Abducens: Purely motor
- Trigeminal: Mixed (sensory and motor)
3. **Determine the Function of Each Nerve**: Understand the primary function of each nerve:
- Vagus: Controls autonomic functions
- Facial: Controls facial expressions and taste
- Abducens: Controls lateral eye movement
- Trigeminal: Controls sensation in the face and chewing muscles
4. **Select the Purely Motor Nerve**: Identify which nerve has only motor functions, which is the Abducens nerve.