When the Radial Muscles of the Iris Contract,the Diameter of the Pupil

Question

When the radial muscles of the iris contract,the diameter of the pupil decreases.

Accepted Answer

When the radial muscles of the iris contract, the diameter of the pupil increases, allowing more light to enter the eye. This is part of the sympathetic response. The contraction of the circular muscles (under parasympathetic control) decreases the pupil diameter.