The Eye Flashcards
Cornea
Transparent part of the eye which refracts light into the eye.
Iris
Pigmented tissue which controls the size of the pupil and therefore how much light enters the eye.
Pupil
Home in the centre of the iris which controls the amount of light entering the eye.
Lens
Focuses light onto the retina.
Retina
Light sensitive part of the eye covered in light-receptors called rods and cones.
Rods
Light receptors which are more sensitive in dim light but can’t sense colour.
Cones
Light receptors concentrated in a small area (fovea) and detect colour (red, blue, green).
Optic nerve
Sensory nerve which carries nerve impulses from the receptors to the brain.
What reflex happens in the dark?
The pupil dilates - the radial muscles are contracted and the circular muscles relaxed, so that more light can enter the eye
What reflex happens in bright light?
The pupil contracts - the radial muscles are relaxed and the circular muscles are contracted, to stop to much light entering the eye and damaging eye.
What happens when we look at a distant object?
The ciliary muscles are relaxed and the suspensory ligaments tighten, in order to pull the lens out to make it thin and focused.
What happens when we look at a close object?
The lens becomes thicker in order to refract the light. The ciliary muscles contract and the suspensory ligaments loosen.
Conjunctiva
Lubricating layer which protects the surface of the eye.
