What part of your nervous system controls for the pupils open and closing in response to light?

The part of the nervous system that controls the opening and closing of the pupils in response to light is the autonomic nervous system, specifically the sympathetic and parasympathetic branches. The parasympathetic nervous system, through the Edinger-Westphal nucleus, constricts the pupils in bright light, while the sympathetic nervous system dilates the pupils in low light conditions. This reflexive response is known as the pupillary light reflex.