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Edexcel IGCSE Biology
draw/describe the structure of the eye
what is the function of the cornea?
transparent lens that refracts light as it enters the eye
function of the iris?
controls how much light enters the pupil
what is the function of the lens?
transparent disc that can change shape to focus light onto the retina
what is the function of the retina?
contains light receptor cells
rods detect light intensity
cones detect colour
what is the fucntion of the optic nerve?
sensory neurone that carries impulses between the eye and brain
what is the function of the pupil?
hole that allows light to enter the eye
what is the ciliary muscle?
a ring of muscle that contracts and relaxes to change the shape of the lens
what are suspensory ligaments?
ligaments that connect the ciliary muscle to the lens
what is the sclera?
the strong outer wall of hte eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye
what is the fovea?
a region of the retina with the highest density of cones (where the eye sees in particularly good detail)
what is the blind spot?
the point at which the optic nerve leaves the eye, where there are no receptor cells
what happens when an object is far away?
light is refracted less
ciliary muscles relax
suspensory ligaments tight
lens thinner
what happens when an object is close?
light is refracted more
ciliary muscles contract
suspensory ligaments slack
lens fatter
what happens to the eye in dim light?
photoreceptors detect change in environment
radial muscles contract
circular muscles relax
pupil dilates
more light enters the eye
what happens to the eye in bright light?
photoreceptors detect change in environment
radial muscles relax
circular muscles contract
pupil constricts
less light enters the eye
Note 
Flashcard (46)