In bright light, impulses from sympathetic neurons cause a constriction of the pupil due to contraction of the radial muscle fibers of the iris.

Question

Quizplus · Accepted Answer

In bright light, impulses from parasympathetic neurons cause a constriction of the pupil due to contraction of the circular muscle fibers of the iris, not the radial muscle fibers which are controlled by sympathetic neurons and cause dilation in low light.

In Bright Light, Impulses from Sympathetic Neurons Cause a Constriction