Topic 6 - The Eye Flashcards
what does the conjunctiva do?
the conjunctiva lubricates and protects the surface of the eye
what does the sclera do?
the sclera is the tough outer layer that protects the eye
what does the cornea do?
refracts light into the eye. its transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface.
what does the iris do?
controls the diameter of the pupil and therefore how much light enters the eye
what does the lens do?
focuses light onto the retina
what is the retina?
the light-sensitive part of the eye. its contains light receptors called rods and cones.
what are rods?
light receptors that are more sensitive in dim light
what are cones?
light receptors that are more sensitive to colours
where are lots of cones found?
in the fovea
what is the optic nerve?
the optic nerve carries impulses from the receptors in the eye to the brain
what happens in the eye when it is exposed to bright light?
circular muscles contract and radial muscles relax to make the pupil smaller
what happens in the eye when it is exposed to dim light?
circular muscles relax and radial muscles contract to make the pupil bigger
what happens in the eye when looking at distant objects?
- ciliary muscles relax, which allows the suspensory ligaments to pull tight
- this makes the lens thin
- so the lens refracts less light
what happens in the eye when looking at near objects?
- ciliary muscles contract, which allows the suspensory ligaments to slack
- this makes the lens fat - more curved
- so the lens refracts more light
why might people be short-sighted?
their cornea/lens bends the light too much or the eyeball is too long. the images are brought into focus in front of the retina
