Medical Surgical Neurosensory Practice Test

Which nerves control the pupillary light reflex?

Afferent CN II and efferent CN II Afferent CN II and efferent CN III Afferent CN III and efferent CN II Afferent CN I and efferent CN III

Correct Answer:

Afferent CN III and efferent CN II

Explanation:

The pupillary light reflex is a two-part pathway: sensory input from the retina travels along the optic nerve to the brain, and the motor output that constricts the pupil travels along the oculomotor nerve. When light hits the retina, signals are carried by the optic nerve to the pretectal area and then to theEdinger‑Westphal nucleus; from there, parasympathetic fibers ride with the oculomotor nerve to the iris sphincter, causing constriction. This wiring explains why shining light in one eye causes both pupils to constrict (the consensual reflex). The olfactory nerve has no role here, and the efferent limb is not carried by the optic nerve. So the correct pairing is afferent input via the optic nerve and efferent output via the oculomotor nerve.

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