Movement of eyeballs is the function of which of the following cranial nerves?

AIIMS Bhopal NO - 2018 (Shift-1st)

Applied Anatomy

Easy

Appeared in: AIIMS Bhopal NO - 2018 (Shift-1st)

Explanation

The Oculomotor nerve (CN III) is the chief motor nerve to the muscles of the eye.
It innervates four of the six extraocular muscles: the superior rectus, medial rectus, inferior rectus, and inferior oblique.
These muscles are responsible for moving the eyeball up, down, medially (inward), and for some rotational movements.
Additionally, the Oculomotor nerve controls the levator palpebrae superioris muscle, which lifts the upper eyelid, and parasympathetic fibers that cause pupil constriction.

Option A: The Optic nerve (CN II) is a sensory nerve, not a motor nerve. Its function is to transmit visual signals from the eye to the brain.
Option B: The Olfactory nerve (CN I) is a sensory nerve responsible for the sense of smell. It has no function related to the eyes.
Option D: The Accessory nerve (CN XI) is a motor nerve that innervates the sternocleidomastoid and trapezius muscles, which are involved in head and shoulder movement.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of Cranial Nerves as background academic context rather than a clinical decision trigger.
Assessing the six cardinal directions of gaze is a fundamental nursing skill used to test the integrity of cranial nerves III, IV, and VI, which control eye movement.
Damage to the Oculomotor nerve (CN III palsy) can result in a characteristic 'down and out' position of the affected eye, ptosis (drooping eyelid), and a dilated pupil. This is a critical finding that can indicate a serious underlying condition like a brain aneurysm or tumor, requiring urgent medical evaluation.
What if? If a patient can only move their eye laterally (outward) and slightly downward, but not up, down, or fully medially, it strongly suggests a palsy of the Oculomotor nerve (CN III), while the Abducens (CN VI) and Trochlear (CN IV) nerves are still functioning.

How to Approach the Question

This is a factual recall question testing knowledge of neuroanatomy.
First, identify the key function described in the question stem, which is 'Movement of eyeballs'.
Next, systematically review the options provided, recalling the primary function of each cranial nerve.
The name 'Oculomotor' itself provides a strong clue, as 'oculo-' refers to the eye and 'motor' refers to movement.
Eliminate the other options based on their distinct functions: Optic is for vision, Olfactory is for smell, and Accessory is for neck/shoulder muscles.
Confirm that the Oculomotor nerve is the primary nerve responsible for controlling most of the muscles that move the eye, making it the correct answer.

Concept Tested & Keywords

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E6 Anatomy Applied Ashalatha 4e p. 425-427

E6 Nursing Fundamentals Potter Perry 12e Part 3 p. 125-127