Chapter contents Overview Somatic motor component Origin, central course Intracranial course Final innervation Visceral motor component Origin and course Final innervation

Cranial Nerve III - Oculomotor Nerve Page 12 of 16 Visceral motor component, pupillary light reflex Light entering the eye causes signals to be sent to the pretectal region of the midbrain via the optic nerve (CN II). The pretectal nucleus in turn projects bilaterally to the Edinger-Westphal nucleus. Preganglionic parasympathetic fibers from each half of the Edinger-Westphal nucleus then project to the ciliary ganglion of the ipsilateral orbit. Post-ganglionic parasympathetic fibers exit the ciliary ganglion to innervate the constrictor pupillae muscle of the ipsilateral eye. Due to the bilateral projections from the pretectal nuclei to the Edinger-Westphal nuclei, light shined into one eye produces pupillary constriction in both eyes. Direct pupillary light reflex - response in the stimulated eye. Consensual pupillary light reflex - response in the opposite eye.

Last revised: March 22, 1998