Final answer:
Neurons from the pretectal area synapse in both CN III parasympathetic nuclei, known as the Edinger-Westphal nuclei, which are involved in regulating the pupillary light reflex by projecting to the ciliary ganglion, affecting iris muscle control.
Step-by-step explanation:
From the pretectal area, neurons synapse bilaterally in both CN III parasympathetic nuclei (Edinger-Westphal). The Edinger-Westphal nucleus serves as the location for parasympathetic neurons that project to the ciliary ganglion. This pathway is an efferent branch component of a reflex arc that regulates pupillary response to light, allowing pupils to constrict or dilate appropriately.
The stimulation of the Edinger-Westphal nucleus leads to the activation of preganglionic parasympathetic fibers that travel with the oculomotor nerve, terminating in the ciliary ganglion. From the ciliary ganglion, postganglionic parasympathetic fibers extend to the smooth muscle of the iris. Hence, the parasympathetic output from this nucleus influences pupillary size and accommodative functions of the eye.