Which nucleus houses the preganglionic parasympathetic neurons that constrict the pupil?

Which nucleus houses the preganglionic parasympathetic neurons that constrict the pupil?

• A. Lateral horn
• B. Edinger Westphal nucleus
• C. Ciliary ganglion
• D. Superior colliculus

Answer: (B)

The pupil constriction reflex is mediated by parasympathetic fibers whose cell bodies are in the Edinger-Westphal nucleus in the rostral midbrain. These preganglionic neurons send their axons with the oculomotor nerve to the ciliary ganglion, where they synapse onto postganglionic neurons that innervate the sphincter pupillae muscle to cause constriction. The lateral horn contains sympathetic preganglionic neurons, not parasympathetic ones for the pupil. The ciliary ganglion holds the postganglionic cell bodies, not the preganglionic ones. The superior colliculus deals with visual processing and reflexive eye movements, not pupil constriction via parasympathetic innervation.

The pupil constriction reflex is mediated by parasympathetic fibers whose cell bodies are in the Edinger-Westphal nucleus in the rostral midbrain. These preganglionic neurons send their axons with the oculomotor nerve to the ciliary ganglion, where they synapse onto postganglionic neurons that innervate the sphincter pupillae muscle to cause constriction.

The lateral horn contains sympathetic preganglionic neurons, not parasympathetic ones for the pupil. The ciliary ganglion holds the postganglionic cell bodies, not the preganglionic ones. The superior colliculus deals with visual processing and reflexive eye movements, not pupil constriction via parasympathetic innervation.