Final answer:
The afferent branch of the pupillary light reflex is through the optic nerve, while the efferent branch involves the oculomotor nerve and the ciliary ganglion.
Step-by-step explanation:
The afferent branch of the pupillary light reflex, which controls the constriction of the pupil to light, involves sensory input through the optic nerve. When light hits the retina, photoreceptors are activated, and the signal is transferred to the retinal ganglion cells that send an action potential along the optic nerve into the diencephalon.
The efferent branch of the reflex involves the oculomotor nerve and the ciliary ganglion. The oculomotor nerve carries the motor response from the brain to the ciliary ganglion in the posterior orbit. From there, the postganglionic fibers project to the circular fibers of the iris and release acetylcholine, which causes the pupil to constrict.