78) Explanation The central visual pathway for the pupillary | Anatomy embryology histology videos & books

78) Explanation

The central visual pathway for the pupillary light reflex is organized as follows: fibers from the ganglionic layer of the retina project posteriorly to the pretectum, which in turn innervates the Edinger-Westphal nucleus. Preganglionic parasympathetic neurons in the EdingerWestphal nucleus project to the ciliary ganglion, which sends postganglionic parasympathetic innervation back to the constrictor pupillae of the eye. The Edinger-Westphal nuclei from each side of the midbrain are also connected to each other by projections running through the posterior commissure. Disconnection of these fibers will result in loss of the consensual pupillary light reflex on the contralateral side, as happens in this case. The habenula (choice B) is a nucleus of the thalamus, which does not participate in the central visual pathways. The lateral geniculate nucleus (choice D) receives fibers from the ganglionic layer of the retina. However, fibers participating in the pupillary light reflex run through this structure without synapsing and terminate in the pretectum. Thus, the lateral geniculate nucleus does not participate in the pupillary light reflex. The inferior colliculus (choice C) and the medial geniculate nucleus (choice E) are components of the auditory system.