the eye. Flashcards
what is the function of the lens?
focuses light on the retina
what is the function of ciliary muscles?
change the shape of the lens for fine focusing
what is the function of the cornea?
the outer surface of the
cornea does most of the focusing of light on to the retina
what is the function of the pupil?
the dark area in the middle of the eye where light enters
what is the function of the iris?
muscles in the iris control the amount of light entering the eye by constricting or dilating the pupil
what is the function of the cones (retina)?
cones are receptor cells that are sensitive to the colour of light
some cones detect red light, while others detect green or blue
information (in the form of wavelengths) from different cones is combined in the brain
what is the function of rods (retina)?
rods are receptor cells that detect differences in light intensity, not colour
rods work well in very dim light whereas cones only work in bright light.
what is the function of the optic nerve?
neurones carry nerve impulses from cones and rods to the brain
what is the eye?
a sense organ
why is colour vision poor in dimlight?
cones only work in bright light as they cannot differentiate the wavelength in dim light
what is colour blindness?
when the cone cells cannot differentiate the wavelengths of red and green light
usually caused by mutations and faulty genetics, and more common in males
why are men more likely to be colour blind?
colour blindness is the result of a faulty x gene, males do not have another x gene whilst women do
what happens when the eye is looking at distant objects?
the ciliary muscle relaxes, which allows the dispensary ligaments to pull tight
this pulls the lens to a less rounded shape, so light is refracted less
what happens when the eye is looking at close objects?
ciliary muscle contracts, which slackens the suspensory ligaments
lens becomes more rounded, so light is refracted more
what is short-sightedness (myopia), what is is caused by and how is it corrected?
objects a short distance away are clear but far-away objects are blurred
caused by the cornea being too round or the eyeball being too long - rays of light are focused in front of the retina
corrected by a diverging concave lens
