Question

Which of the following cranial nerve is instrumental in motor function:

• A. \( \text{Vestibulocochlear} \)
• B. \( \text{Olfactory} \)
• C. \( \text{Accessory} \)
• D. \( \text{Optic} \)

Hint:

Cranial nerves involved in motor functions include: 
1. Oculomotor (III): Eye movement. 
2. Trochlear (IV): Eye movement. 
3. Abducens (VI): Eye movement. 
4. Accessory (XI): Neck and shoulder movements. 
5. Hypoglossal (XII): Tongue movement.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Cranial nerves are grouped into sensory, motor, and mixed types based on what kind of signal they carry, and the question asks for the one built for motor function.

Step 2: Key Formula or Approach:
Check each nerve for the direction of its main signal: does it carry information from a sense organ into the brain (sensory), or does it carry commands from the brain out to a muscle (motor).

Step 3: Detailed Explanation:
Vestibulocochlear (VIII) carries hearing and balance signals inward from the inner ear. Olfactory (I) carries smell signals inward from the nose. Optic (II) carries vision signals inward from the retina. All three only move information toward the brain.
Accessory (XI) is different. It starts in motor nuclei in the brainstem and spinal cord and travels outward to the sternocleidomastoid and trapezius muscles, driving head turning and shoulder movement.

Step 4: Final Answer:
Since Accessory is the only nerve in the list that sends outgoing motor commands to muscles, it is the nerve responsible for motor function.