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 cranial nerve classifications. Cranial nerves are classified based on their primary functions: 
1. Sensory nerves (e.g., Olfactory and Optic) are involved in sensation. 
2. Motor nerves (e.g., Accessory) control muscle movements. 
3. Mixed nerves (e.g., Facial) have both sensory and motor functions. 

Step 2: Role of the accessory nerve. The accessory nerve, also known as cranial nerve XI, is a motor nerve that innervates the sternocleidomastoid and trapezius muscles. It facilitates movements of the head, neck, and shoulders. 

Step 3: Comparison with other options. - Option \( (A) \): Vestibulocochlear nerve (cranial nerve VIII) is a sensory nerve responsible for hearing and balance. 
- Option \( (B) \): Olfactory nerve (cranial nerve I) is a sensory nerve responsible for the sense of smell. 
- Option \( (D) \): Optic nerve (cranial nerve II) is a sensory nerve responsible for vision. 

Conclusion: The accessory nerve (cranial nerve XI) is the correct answer for being instrumental in motor function.

Answer 2

This question asks which cranial nerve mainly controls movement. A quick way to work through it is to recall the primary job of each nerve listed, since cranial nerves are grouped as sensory, motor, or mixed.

1. Vestibulocochlear: This is cranial nerve VIII. It carries signals for hearing and balance from the inner ear to the brain, making it a purely sensory nerve with no motor fibers.
2. Olfactory: This is cranial nerve I. It carries smell signals from the nose to the brain and is also purely sensory.
3. Accessory: This is cranial nerve XI. Unlike the other three options, it carries motor fibers to the sternocleidomastoid and trapezius muscles, letting a person turn the head and shrug the shoulders.
4. Optic: This is cranial nerve II. It carries visual signals from the retina to the brain and, like the olfactory and vestibulocochlear nerves, is purely sensory.

Three of the four nerves listed only carry sensory information inward to the brain, while one carries motor commands outward to muscles.

Therefore, the correct answer is Accessory.