Topic 2 – Cells and Control-The Eye Flashcards
outline structure and function of the cornea
transparent outer covering of eye
refracts light entering eye
outline structure and function of iris
pigmented ring of circular muscles and radial muscles
controls size of pupil to alter how much enters eye
what is pupil?
hole in iris centre that allows light rays to enter eye
outline structure and function of lens
transparent, biconvex structure
suspensory ligaments attach lens to ring of ciliary muscle
refracts light, focusing onto retina
what is function of ciliary muscles and suspensory ligaments?
changes shape of lens (accommodation) to focus light onto retina
outline structure and function of retina
light sensitive layer composed of rod and cone cells
converts light energy into neural signals which are sent to brain via optic nerve
what are rod cells?
cells in retina that are sensitive to low light intensity (dim light)
what are cone cells?
cells found in retina that are sensitive to high light intenisty and can detect different colours
what is function of optic nerve?
transmits nerve impulses to brain from retina.
describe how dim light affects size of pupil?
light receptors detect dim light circular muscles relax radial muscles contract pupil dilates more light enters pupil
describe how bright light affects size of pupil?
light receptors detect bright light circular muscle contract radial muscles relax pupil contracts less light enters pupil
why is iris reflex important?
prevents bright light from damaging retina
what is accommodation?
process by which elastic lens change its shape to focus on distant objects
light is focused onto the retina
describe how eye focuses on close objects
close object ciliary muscles contract suspensory ligaments slacken lens become more round light is more refracted light rays focus onto retina
describe how eye focuses on distant objects
distant object ciliary muscles relax suspensory ligaments tighten lens less round light is refracted less light rays focused onto retina
what is long sightedness?
can focus on distant objects clearly
cannot focus on near objects
what are causes of long sightedness?
eyeball too short
lens is less elastic, so light ray are not focused onto retina, instead behind the retina/
how is long sightedness treated?
using convex lens
replacement lenses
laser eye surgery
what is short sightedness
can focus on near objects clearly
cannot focus on distant objects
what are causes of short sightedness
eyeball to long
lens too thick and too rounded, so light ray are not focused onto retina, so focus in front of retina
how is short sightedness treated?
using concave lens
replacement lenses
laser eye surgery
what are cataracts?
cloudy patch forms on lens of eye which affects vision
vision becomes blurry, difficult to see intensity of colour, problem with glare.
how are cataracts treated?
clouded lens exchanged for a synthetic lens during surgery.
what is colour blindness?
deficiency of eye that makes it hard to distinguish between colours
individuals with red green colour have difficulty differentiating red and green
what is cause of colour blindness
damage to cone cells in retina
