12.2 Photoreception Flashcards
External layer of the eye:
Sclera
cornea
Intermediate layer of the eye
choroid
iris
pupil
ciliary muscle
Internal
retina
rods/cones
optic nerve
sclera
white tough fibrous protective layer
cornea
where the light enters the eye
transparent part of the sclera at the front of the eye
Choroid
Absorbs stray light rays that are not detected by photoreceptors
contains blood vessels that nourish the eye
Iris
Allows light to enter by adjusting the size of the pupil
pupil
the hole
adaptation
The iris adjusting the size of the pupil; based on light conditions
retina
thin layer of tissue that contains the photoreceptors rods/cones
rods
sensitive to light intensity
more concentrated on the edges
cones
sensitive to different colours
most densely found in the fovea centrlalis
optic nerve
where the rods and cones send sensory impulses to the brain
Aqueos humour
a clear watery fluid that maintains the shape of the cornea and provides oxygen and nutrients for the surrounding cells including those of the lens and cornea
vitreous humour
jelly like fluid that helps maintain the shape of the eyeball
Accommodation (2)
the ability of the lens to change shape ignorer to focus images clearly on the retina
- a reflex
Astigatism
Uneven curvature of part of the cornea. Because the cornea is asymmetrical it cannot bend light rays so that they meet at the correct focal point
Myopia
Eyeball enlongated
- focused light falls infront of the retina instead of the photoreceptors
nearsighted
Hyperopia
farsighted
eyeball is too short
light falls behind the retina
how do photoreceptors relay visual info to the brain?
rods and cones send neurotransmitters that inhibit messages. When stimulated they stop sending neurotransmitter that inhibit and the bipolar cells become depolarize and sends message to ganglion cells which ends form the optic nerve.
