Which statement about the ciliary ganglion is true?

Which statement about the ciliary ganglion is true?

• A. It contains postganglionic sympathetic neurons that innervate the iris dilator.
• B. It contains preganglionic parasympathetic neurons synapsing there.
• C. It contains postganglionic parasympathetic neurons that innervate the sphincter pupillae and ciliary muscle.
• D. It receives somatic motor neurons to the eye.

Answer: (C)

The ciliary ganglion is a relay in the orbit for parasympathetic signals. Preganglionic parasympathetic fibers from the Edinger-Westphal nucleus travel with the oculomotor nerve and synapse in this ganglion. The postganglionic parasympathetic neurons then send fibers with the short ciliary nerves to innervate the sphincter pupillae (pupil constriction) and the ciliary muscle (lens accommodation). This arrangement means the ganglion contains cell bodies of postganglionic parasympathetic neurons that control those two structures. That’s why the statement identifying postganglionic parasympathetic neurons innervating the sphincter pupillae and ciliary muscle is correct. The other options don’t fit: sympathetic postganglionic fibers to the iris come from the superior cervical ganglion and do not synapse in the ciliary ganglion; the preganglionic parasympathetic cell bodies are in the brainstem (not in the ganglion); and somatic motor neurons to the eye do not travel through this autonomic ganglion.

The ciliary ganglion is a relay in the orbit for parasympathetic signals. Preganglionic parasympathetic fibers from the Edinger-Westphal nucleus travel with the oculomotor nerve and synapse in this ganglion. The postganglionic parasympathetic neurons then send fibers with the short ciliary nerves to innervate the sphincter pupillae (pupil constriction) and the ciliary muscle (lens accommodation). This arrangement means the ganglion contains cell bodies of postganglionic parasympathetic neurons that control those two structures.

That’s why the statement identifying postganglionic parasympathetic neurons innervating the sphincter pupillae and ciliary muscle is correct. The other options don’t fit: sympathetic postganglionic fibers to the iris come from the superior cervical ganglion and do not synapse in the ciliary ganglion; the preganglionic parasympathetic cell bodies are in the brainstem (not in the ganglion); and somatic motor neurons to the eye do not travel through this autonomic ganglion.