L4 Retinal Processing Flashcards
What is the main purpose of the sclera?
light reflection
What is the main purpose of the retina?
It is where light perception takes place
What is accommodation?
It is changes in the lense shape to refract light @ the correct angle in distance and near vision
Where is the focal point in emmetropia (normal vision)?
at the retina
Where is the focal point in myopia (near sighted)?
ahead of the retina
Where is the focal point in hyperopia (farsighted)?
behind the retina
Where is the region of high visual acuity?
fovea
Where is the fovea located?
w/in the macula lutea
What is the blind spot of the eye?
the optical disk or papilla
Why don’t we notice the blind spot in our eyes?
Our eyes are always moving the make up for the blind spot
What is the visual field ?
what you are actually looking at in space
What is the retinal field?
How visual field is projected on to the retina
What is the relationship b/n the retinal and visual field?
the retinal field is the visual field upside down and backwards
Why does the inf. field require more peripheral monocular vision?
b/c our vision is partially blocked by our nose
Where does optical cross over occur?
at the optic chiasm
What are the 2 types of photorecptors?
rods and cones
What would cause complete vision loss?
damage to the optic nerve
Where are the photoreceptive components located?
in the the epithelial cells
T/F photoreceptive aspects of rods and cones don’t need to be recycled
False, they do need to be recycled
What is the chem. in rods that abs. light?
Rhodopsin
What are the two diff. b/n rods and cones?
- Which chem is present
- what wavelength of light they respond to
When are photoreceptors depolarized?
in the dark
What happens when photoreceptors are depol?
Glutamate is released
Na+ chnls are open
What causes photoreceptors to hyperpol?
Light
What happens when photoreceptors are exposed to light?
No glutamate prod.
Na+ chnls close
what % of vitamin A is stored in the liver?
50-85%
T/F Vit A is essential for signaling an recycling
true
What is the major structural diff b/n rods and cones?
Rods have a larger photoreceptive area
What type of ganglion are NMDA receptors assoc w?
Off-center
What type of ganglion are mGLU receptors assoc w?
On center
What are functional ganglion responses due to?
bipolar cell responses via glutamate
T/F glutamate is only inhibitory
false, it is inhibitory and excitatory
What variables determine receptive fields of retina?
duration of spot illlumin.
size of spot illumin.
background light intensity
Where are cones located?
macula zone
Comparing rods and cones, which is more abundant overall?
Rods
What do rods sense?
light
What do cones sense?
color and detail
what are luminance units?
candela (cd) / unit area (m^2)
What is most active during scotopic function?
only rods
What is most active during mesopic function?
rods and cones are equally active
What is most active during photopic function?
only cones
What is protanopia?
loss of red opsins
What is deuteranopia?
loss of green opsins
What is trichromat?
having all three opsins
What types of synapses are in the retina?
chemical and electrical
Amacrine cells have lateral receptors. Why?
for identification of motion and shape
What cells release GABA in lateral information flow?
horizontal cells
What is the point of lateral inhibition?
promotes contrast enhancement and edge detection
What type of signaling does lat. inhibition rely one?
Gap junctions
What is retinal prosthesis?
inserting a computer chip directly in the retina to relay to the nerve
What is the difference b/n retinal and cortical prosthesis?
retinal is in the retina
cortical is from the visual cotex
What encodes the visual scene?
retinal ganglion cells which are processed in the visual cortex
