eye and ear
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tough outer coat of eye, visible white coat
sclera
transparent window which allows light to enter eye
cornea
coloured ring of tissue
iris
hole which lets light through
pupil
dark layer underneath sclera which contains many pigment cells and blood vessels
choroid
place where light energy is converted to nerve impulses at back of the eye
retina
nerve which carries impulses to brain
optic nerve
place where cones are concentrated
fovea
how does pupil constrict when bright light enters
circular ms contract and radial ms relax
what are the adv of having 2 eyes
cancelling blind spot wider field of vision stereoscopic vision better sense of distances
what are the changes that occur that allow distant objects to be seen
ciliary ms relax suspensory ligaments are pulled tight lens flat
state cause, result and method of correction for long sight
cause: lens not convex enough or eyeball too short result: light focused beyond retina method of correction: convex lens to converge light before it enters the eye
state cause, result and method of correction for short sight
cause: lens too convex or eye ball too long result: light focused short of retina method of correction: concave lens to converge lens before it enters the eye
discuss the differences between regular and irregular astigmatism
regular: occurs when surface of cornea or lens is not perfectly spherical but rounder in one direction than the other person’s eye will be in focus in one direction but not the other corrected by glasses or lenses irregular: curvature of cornea or lens is in more than one direction corrected by lenses only
what is a cataract and how is it treated
a condition in which the lens becomes cloudy and opaque so person is unable to see can only be treated by surgery lens is replaced by artifical lens
outer ear function
directs sound waves to ear drum
3 small bones that allow vibrations to pass and amplify vibrations
malleus, incus and stapes (ear ossicles)
function of euctachian tube
connects middle ear with throat and this allows pressure to be equalized either side of the ear drum
where are receptor cells that convert vibrations to nerve impulses found
organ of cort
part of ear which senses balance
semi circular canals