Question

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

• A. Vestibulocochlear
• B. Olfactory
• C. Accessory
• D. Optic

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Cranial nerves can be purely sensory, purely motor, or mixed, and the question asks which of the four listed nerves is a motor nerve.

Step 2: Key Concept or Approach:
Check the known function of each cranial nerve individually, since three of the four are dedicated sensory nerves for the special senses.

Step 3: Detailed Explanation:
The olfactory nerve, cranial nerve I, only carries smell information and has no motor fibers.
The optic nerve, cranial nerve II, only carries visual signals from the eye and is also purely sensory.
The vestibulocochlear nerve, cranial nerve VIII, only carries hearing and balance information from the inner ear, again purely sensory.
The accessory nerve, cranial nerve XI, is different: it is a purely motor nerve that controls the sternocleidomastoid and trapezius muscles, letting a person turn the head and shrug the shoulders.

Step 4: Final Answer:
The accessory nerve is the cranial nerve instrumental in motor function among the given options.