Neurophysiology and special senses: pupillary light reflex: practice question

The best answer is C, Pretectal area, interrupting the light reflex pathway. The light reflex passes through the pretectal nuclei to both Edinger-Westphal nuclei, whereas accommodation uses a cortical pathway that bypasses the pretectum.

The Edinger-Westphal nucleus serves both reflexes, so its lesion would abolish both.

A ciliary ganglion lesion would impair both responses and cause a tonic pupil.

The oculomotor nerve carries both pathways, so a lesion would impair both.

It tests Neurophysiology and special senses: pupillary light reflex in Physiology. A pretectal lesion therefore abolishes the light reflex and spares the near response, as in Argyll Robertson pupils.

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

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