Chapter 12 - Coordination and Response : Human Eye

Cones

enable us to see colours in bright light.

Rods

enable us to see in dim light but only in black and white.

Tear gland

Secretes tears which lubricate the eye, nourish the cornea and keeps it free from dust.

Eye lashes

Shield eyes from dust particles.

Iris

Contain radial and circular muscles that control the size of pupil

Pupil

Allows light to enter the eye

conjunctiva

Thin, transparent mucous membrane that covers the sclera

Cornea

Transparent refractive layer covering the iris and pupil.

Choroid

Middle layer of the eyeball, between the sclera and retina.

Retina

Innermost layer of the eyeball which contains photoreceptors, which are connected to the optic nerve.

Lens

Transparent biconvex structure that refracts light onto the retina.

Fovea

Also called yellow spot, a small depression in the retina where images are usually focused

Suspensory ligaments

Connects the ciliary body to the lens

Optic nerve

Transmits signal from the retina to the brain.

Photoreceptors

consist of rods and cones.

Vitamin A

The vitamin required for the formation of visual purple

Accommodation

A reflex action where the lens is adjusted so that clear images of objects at different distances are formed on the retina.

Pupil reflex

Reflex action (involuntary) where the pupil changes size in response to changes in light intensity.