Edinger-Westphal nucleus

The Edinger-Westphal nucleus is a group of cells located in the midbrain that plays a crucial role in the parasympathetic nervous system. This nucleus is part of the pathway that controls involuntary functions, specifically those related to the eye.12

The Edinger-Westphal nucleus contains parasympathetic preganglionic neurons. These neurons send out axons that travel with the oculomotor nerve (cranial nerve III) to the ciliary ganglion in the orbit. From the ciliary ganglion, postganglionic fibers innervate two key structures in the eye: the sphincter muscle of the iris and the ciliary muscle.23

This neural pathway is essential for two primary functions:
* Pupillary constriction: The innervation of the iris sphincter muscle causes the pupil to constrict, regulating the amount of light entering the eye. This is a key part of the light reflex.13
* Accommodation: The innervation of the ciliary muscle allows the eye to change the shape of the lens, enabling focus on nearby objects.13