Acetylcholine, released by parasympathetic nerve fibers innervating the iris sphincter muscle, causes pupillary constriction, also known as miosis. This process reduces the amount of light entering the eye.
The pupillary light reflex, mediated by this neurochemical interaction, is essential for protecting the retina from excessive light and enhancing visual acuity in bright conditions. It’s a crucial diagnostic tool for assessing neurological function, as disruptions can indicate underlying issues within the brainstem or peripheral nervous system. The study of this mechanism has contributed significantly to our understanding of the autonomic nervous system and its role in regulating physiological processes.
