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The nervous system – WJECThe eye

Our nervous system allows us to detect and react to changes in the environment. Sense organs, like the eyes, detect changes and our central nervous system co-ordinates a response.

Part of Biology (Single Science)Variation, homeostasis and micro-organisms

The eye

The eye is a sense organ that responds to light.

A cross section of the human eye, labelled.

Structure	Function
Cornea	Clear area of the sclera, it refracts light - bends it as it enters the eye.
Iris	Muscles which alter the size of the pupil, controlling the amount of light entering the eye.
Lens	Focuses light onto the retina.
Retina	Contains the light receptor cells.
Optic nerve	Carries impulses between the retina and the brain.
Sclera	White, tough outer layer.
Choroid	Pigmented middle layer with many blood vessels. It absorbs light to avoid reflection and nourishes the retina.
Blind spot	Where the optic nerve leaves the retina so lacks receptor cells.
Pupil	Small hole at the centre of the iris through which light enters the eye.

Structure	Cornea
Function	Clear area of the sclera, it refracts light - bends it as it enters the eye.

Structure	Iris
Function	Muscles which alter the size of the pupil, controlling the amount of light entering the eye.

Structure	Lens
Function	Focuses light onto the retina.

Structure	Retina
Function	Contains the light receptor cells.

Structure	Optic nerve
Function	Carries impulses between the retina and the brain.

Structure	Sclera
Function	White, tough outer layer.

Structure	Choroid
Function	Pigmented middle layer with many blood vessels. It absorbs light to avoid reflection and nourishes the retina.

Structure	Blind spot
Function	Where the optic nerve leaves the retina so lacks receptor cells.

Structure	Pupil
Function	Small hole at the centre of the iris through which light enters the eye.

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