Why Pupils Dilate

Why do your pupils get huge in the dark and sometimes when you are excited

or attracted to someone? It is your body’s built-in camera exposure system.

Your pupil is the opening that lets light into your eye, bigger opening,

more light. The iris controls pupil size using TWO muscles: a squeeze ring

and a pull-open muscle. Bright light triggers the pupillary light reflex,

your parasympathetic system makes the ring muscle tighten, shrinking the pupil. In the dark,

the opposite happens: sympathetic signals activate the dilator muscle, widening the pupil to capture more

light. Here is the wow part: emotions can also nudge this system,