Iris

Definition

The iris is the colored part of the eye that surrounds the pupil and controls the amount of light entering the eye by adjusting the size of the pupil. It is composed of muscular fibers that constrict or dilate to regulate light intake, aiding in visual perception.

Related terms

Pupil: The opening in the center of the iris through which light enters the eye.

Retina:

A layer at the back of the eyeball containing cells sensitive to light that trigger nerve impulses that pass via the optic nerve to the brain, where a visual image is formed.

Somatic Nervous System:

The part of the peripheral nervous system associated with voluntary control of body movements via skeletal muscles and sensory reception