Sphincter Pupillae
Eye
Constricts the pupil in bright light — blocked by atropine (the 'belladonna' drug), which dilates pupils for eye exams and was used cosmetically in the Renaissance.
Function
Pupil constriction (miosis)
Origin
Circular smooth muscle of iris
Insertion
Fibers encircle pupil
Innervation
Parasympathetic fibers from CN III via ciliary ganglion