Walsh & Hoyt: The Efferent Arc of the Pupil Light Reflex

Abstract

All neural impulses that reach the sphincter of the pupil travel via a preganglionic parasympathetic pathway from the rostral midbrain to the ciliary ganglion in the orbit and then to the iris sphincter muscle via a postganglionic pathway within the short ciliary nerves. Midbrain parasympathetic outflow pathway. Visceral oculomotor nuclei. Pupillary fibers in teh oculomotor nerve. Sympathetic outflow pathway. Hypothalamus. Brain stem and spinal cord sympathetic pathways. Preganglionic sympathetic fibers. Superior cer vical ganglion. Postganglionic sympathetic pathway. Peptidergic innervation to the iris