Optic cranial nerve is a?

Appeared in: NIA - 29 January 2023

Explanation

The Optic nerve (Cranial Nerve II) is classified as a special sensory nerve.
Its sole function is to transmit visual impulses from the retina of the eye to the brain.
It contains only afferent (sensory) fibers and lacks any motor (efferent) fibers for muscle movement.

Option B: Motor nerves (efferent nerves) carry signals from the brain to muscles or glands to produce movement or secretion. The optic nerve only carries sensory information to the brain.
Option C: Nerves with both sensory and motor functions are called mixed nerves. The optic nerve is purely sensory.
Option D: This option is incorrect because the optic nerve has a very specific classification as a sensory nerve.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of cranial nerves by function (sensory, motor, mixed) as background academic context rather than a clinical decision trigger.
Assessing the optic nerve (visual acuity, visual fields) is a core component of a neurological exam, helping nurses detect vision loss, glaucoma, or signs of increased intracranial pressure like papilledema.
The pupillary light reflex tests both CN II (sensory input) and CN III (motor output). An abnormal finding can help a nurse pinpoint the location of a neurological lesion.
What if? If a patient can see light with their right eye (intact CN II) but the right pupil does not constrict, while the left pupil does (consensual response), the problem is likely with the efferent pathway of the right eye, i.e., the Oculomotor nerve (CN III), not the Optic nerve.

How to Approach the Question

Identify the core subject of the question: 'Optic cranial nerve'.
Recall the primary function associated with this nerve. The optic nerve is fundamentally linked to the sense of sight (vision).
Classify this function. Vision is a sensory input. Therefore, the nerve is sensory.
Consider if the nerve has other roles. Does it move any muscles? No. Therefore, it is not motor.
Conclude that the nerve is purely sensory and select the corresponding option.

Concept Tested & Keywords

Concept Tested: Classification of cranial nerves by function (sensory, motor, mixed)
Stem keywords: Optic cranial nerve
Lead-in keywords: is a

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E6 Anatomy Applied Ashalatha 4e p. 425-427

E6 Physiology Essentials Sembulingam 10e Part 3 p. 32-34

E6 Anatomy Grays 43e Vol 1 Part 3 p. 34-36

Practise the full NIA - 29 January 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.