The Eye Flashcards
sensory receptors
cells or groups of cells in sense organs that respond to stimuli
what do the receptors do
they convert the energy of the stimuli into electrical impulses which travel along the sensory neurons to the brain as nerve impulses
what do nerve impulses do
they cause sensations in the brain, and the brain interprets these giving us the perception of light or sound
how can you distinguish between what type of impulse it is
from the part of the brain that receives the impulse
2 types of sensory receptors
exteroreceptors
interoreceptors
exteroreceptors
respond to information from the outside if the body e.g light/sound
interoreceptors
respond to information in the body’s internal environment e.g CO2 level in blood, blood pressure etc.
the senses
hearing sight smell taste touch (pressure, cold, heat,pain)
function of the eyelids
cover and protect the eyes
function of blinking
spreads fluid over the surface and keeps it moist
tear glands
secrete fluid to keep eyes moist, to wash away dust and bacteria
conjunctiva
a thin transparent membrane that covers the front of the eye and protects it
eye muscles
allow movement of the eye in the eye orbit
what is the sclera
the white of the eye, a tough layer that prevents entry of light
function of sclera
protects and gives shape to the eye
what is the cornea
front part of the sclera that is transparent and lets light in
what is the iris
coloured part of the eye in front of the lens
function of the iris
muscles in the iris contract in response to changes in light intensity, this changes the size of the pupil and controls the amount of light entering the eye
what is the pupil
a hole in the centre of the iris
function of pupil
to allow light to enter the eye
bright light
small pupil
dim light
large pupil
function of the suspensory ligaments
hold the lens in place (attach the lens to the ciliary body)
lens
transparent, flexible body
function of lens
to focus light onto the retina (changing shape)
function of the ciliary body
contains the ciliary muscle which changes the shape of the lens
chloroid
a layer of pigmented cells at the back of the eye containing blood vessels and melanin
function of blood vessels
to supply the eye
function of melanin
black pigment to absorb light and prevent reflection of light within the eye
retina
innermost layer of the eye containing light-receptor cells - the cones and rods
function of light receptor cells
convert light into nerve impulses
cones
function in bright light (daylight vision) capable of colour vision (blue, red or green)
rods
function in dim light (night vision) capable of black and white vision only
visual pigments in cones and rods
Iodopsin and Rhodopsin
vitamin A is needed for
synthesis of Rhodopsin
lack of vitamin A leads to
night blindness
fovea (yellow spot)
small area at the centre of the retina containing cones only
function of fovea
the area of the sharpest, most detailed vision, most light i focused here to form images
blind spot
a small region of the retina where optic nerve fibres leave the back of the eye - it does not have cones or rods and so it is not sensitive to light
optic nerve
bundle of sensory nerve fibres that leave the back of the eye
function of the optic nerve
carries nerve impulses from the retina to the brain - the brain interprets these impulses
aqueous humour
watery solution that fills the front part of the eye
function of aqueous humour
maintains the shape of the front part of the eye
vitreous humour
jelly-like material that fills the back part of the eye
function of vitreous humour
gives shape to the eye and supports the lens
advantage of having 2 eyes
to judge distnce or give 3-D image
to increase the field of view
2 eye defects
short sightedness (myopia) long sightedness
myopia
unable to focus distant objects clearly
cause of myopia
distance between lens and retina is too long
correction of myopia
wearing diverging lens
long sightedness
unable to focus near objects clearly
cause of long sightedness
small eye balls or weak lens
correction of long sightedness
wearing converging lens
