Ch. 4 Reception of Visual Input

Pupil

Regulates the amount of light that passes through the cornea and the lens.

Lens

A transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused onto the retina.

Retina

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

Rods

Located in the retina, act as our primary photoreceptors in conditions of poor lighting and for dim, or night vision. They are sensitive to very low levels of illumination.

Cones

Located in the retina, allow us to see objects in fine detail, and allow us to detect colors. They are stimulated only at high levels of illumination, and are more suited for day vision.

Optic nerve

Electrical impulses leave the eye via this structure, which transmits impulses directly to the brain.

Optic chiasm

The point at which the crossing of nerve fibers takes place.

Lateral geniculate nucleus

The greatest percentage of optic nerve fibers synapse in this specialized area of the thalamus. Visual impulses are relayed from here to the primary visual cortex.