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Paper 2 ✅
B5 - Homeostasis and Response
5.4 - Eyes (Structure)
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Cards (12)
Cornea
:
Transparent
No blood vessels (to get the oxygen it needs, oxygen has to
diffuse
through the cornea)
Refracts
light slightly
Iris
:
Coloured bit of eye
Controls how big or small the
pupil
is
Pupil
:
gap in the middle of the
iris
allows light to pass through to the
lens
Lens
:
refracts
light
can change its shape so light focuses on the
retina
Retina
:
made up of two receptor cells -
cone cells
(colour, don’t work in low light) and
rod cells
(sensitive, only see black and white)
Fovea
:
only
cone cells
try to focus light on it as it is clearest
Optic Nerve
:
takes impulses generated by
receptor cells
to the brain to be interpreted
Iris Reflex
:
Bright Light
- Constricted (
contracted
circular muscles,
relaxed
radial muscles)
Low Light
-
Dilated
(relaxed circular muscles, contracted radial muscles)
What is the cornea?
S
transparent
layer at the front of the eye which
refracts
light
Which two stimuli are the receptor cells of the eye sensitive to?
Colour
Light intensity
What is the purpose of the iris reflex?
To ensure the
optimum
amount of light enters the eye
When the eye is exposed to bright light, will the
pupil
constrict
or dilate?
Constrict