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Cornea
Outer cover where light first passes through
Pupil
Small adjustable opening in the iris
Iris
muscles that dilate/restrict pupil
Lens
focuses light into an image projected onto retina
Retina
Fovea
Tiny pit filled with cones
Optic Nerve
thick rope of intertwined ganglion axons
Blind Spot
area without visual receptors because it's where blood vessels and nerves connect to eyeball
1) Photoreceptor Cells
Rods
Rods
What kind of photoreceptor cell works best at night?
Rods
what kind of photoreceptor cell is responsible for peripheral vision?
Cones
Cones
What kind of photoreceptor cells work best at daytime/in bright light?
Cones
What kind of photoreceptor cells are responsible for detailed vision?
2) Bipolar Cells
3) Ganglion Cells
Visual Cortex in Occipital Lobe
Final Destination of visual neural message?
Trichromatic Theory
“there are only 3 types of photoreceptors, so we can only see red, green, and blue”
BUT
“when combined, these photoreceptors allow us to see ALL colors of light”
Opponent-Process Theory
“2 sets of firing neurons that work in opposite ways”
ex. see blue → blue cones fire → neurons connected to those blue cones fire (excitatory messages) while orange gets suppressed (inhibitory messages)
evidence: afterimage (seeing opposite colors after staring at a color for awhile)
when excitatory signal disappears, the inhibitory briefly overshoots (out of balance)
Light Adaptation
adjusting to brighter light
Dark Adaptation
adjusting to dimmer light
Near-sightedness
people can only see what’s near their eyes
Far-sightedness
distant objects are clearer and near objects are blurry
Cataracts
cloudy lenses
Glaucoma
excess fluid in eye presses on optical nerve so it can’t fire
Color blindness
blindness
can be result of damage to eye, neurons, or visual cortex