Neuro: pupillary light reflex pathway: practice question

A Ophthalmology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Ophthalmology · Neuro: pupillary light reflex pathway

Sample item

Which sequence correctly traces the afferent and efferent pathway of the pupillary light reflex?

AOptic nerve, pretectal nucleus, Edinger-Westphal nucleus, oculomotor nerve, ciliary ganglion, sphincter pupillaeBOptic nerve, lateral geniculate body, visual cortex, oculomotor nerveCOptic nerve, hypothalamus, superior cervical ganglion, sphincter pupillaeDOptic nerve, superior colliculus, trochlear nucleus, dilator pupillae

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Optic nerve, pretectal nucleus, Edinger-Westphal nucleus, oculomotor nerve, ciliary ganglion, sphincter pupillae

The afferent limb is the optic nerve, with fibres bypassing the lateral geniculate to the pretectal nuclei, then to both Edinger-Westphal nuclei, giving the consensual response, and the efferent limb through the oculomotor nerve and ciliary ganglion to the sphincter. Cortical lesions do not affect the reflex.

Option by option

A. Optic nerve, pretectal nucleus, Edinger-Westphal nucleus, oculomotor nerve, ciliary ganglion, sphincter pupillae (correct)
Correct. This is the reflex arc.
B. Optic nerve, lateral geniculate body, visual cortex, oculomotor nerve
The reflex does not involve the geniculate or visual cortex.
C. Optic nerve, hypothalamus, superior cervical ganglion, sphincter pupillae
The sympathetic pathway through the superior cervical ganglion supplies the dilator.
D. Optic nerve, superior colliculus, trochlear nucleus, dilator pupillae
The superior colliculus and trochlear nucleus are not part of it.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Ophthalmology question

What is the answer to this Ophthalmology question?

The best answer is A, Optic nerve, pretectal nucleus, Edinger-Westphal nucleus, oculomotor nerve, ciliary ganglion, sphincter pupillae. The afferent limb is the optic nerve, with fibres bypassing the lateral geniculate to the pretectal nuclei, then to both Edinger-Westphal nuclei, giving the consensual response, and the efferent limb through the oculomotor nerve and ciliary ganglion to the sphincter.

Why is "Optic nerve, lateral geniculate body, visual cortex, oculomotor nerve" not the answer?

The reflex does not involve the geniculate or visual cortex.

Why is "Optic nerve, hypothalamus, superior cervical ganglion, sphincter pupi…" not the answer?

The sympathetic pathway through the superior cervical ganglion supplies the dilator.

Why is "Optic nerve, superior colliculus, trochlear nucleus, dilator pupillae" not the answer?

The superior colliculus and trochlear nucleus are not part of it.

What concept does this question test?

It tests Neuro: pupillary light reflex pathway in Ophthalmology. Cortical lesions do not affect the reflex.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neuro: pupillary light reflex pathway?

Group the red eye by what to examine and what the pupil does. Then use the flashcards and the other Ophthalmology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.