The eye Flashcards
cornea
completely transparent
no blood vessels
refracts light (always by the same amount)
first structure light meets
pupil
not a structure
gap in middle of iris
iris
colour of eye
determines size of pupil
made up of circular and radial muscles
lens
refract light
can change shape
-changes depending on how strongly light needs to be refracted
- so light is refracted to hit retina
retina
made of two diff receptor cells
cone cells
rod cells
cone cells
sensitive to colour of light
allow us to see in colour
dont work well in low light conditions
rod cells
more sensitive to light
only allow us to see in black and white
fovea
spot on retina that only has cone cells
spot we try to focus light on to see most clearly
optic nerve
takes all impulses generated by receptor cells and transmits them to the brain
making pupil smaller
circular muscles contract
- squeezing pupil smaller
radial muscles relax
- so they can be stretched over a larger space
making pupil larger
circular muscles relax
radial muscles contract
- make them shorter
- pulling pupil open
pupil in bright light
can be damaging to retina
pupil gets smaller to allow less light in
pupil in low light
gets larger
allows more light in
allows us to see in dark
accommodation
reflex that changes refractive power of lens
looking at nearby objects
ciliary muscle contracts
- inwwards towards lens
- suspensory ligaments slacken
- no longer pulling on lens so it can return to its
natural, fatter shape
- light is refracted more strongly
