Exam2Lec4Vision:RetinalProcessing Flashcards
(64 cards)
1
Q
What is the region of high visual acuity in the eye?
A
macula/fovea
2
Q
What is the blindspot of the eye?
A
optic disk
no receptors, this is where cells/axons leave retina to become part of the optic nerve
3
Q
What is the vascular supply of the eye?
A
branch of opthalmic artery and branch of opthalmic vein
4
Q
Most of our vision is ____
A
binocular
this is central vision (both eyes)
5
Q
Most of our peripheral vision is____
A
monocular
one eye
6
Q
Where is light absorbed?
A
retina
light perception begins at retina
7
Q
How can the lens accomodate when light info enters?
A
It can change shape so that the light is refracted at the correct angle onto the retina
lens help focus light
8
Q
To see far, what how does the eye accomodate?
A
- Ciliary muscle relaxes
- suspensory ligament taut
- lends flattens/thins
9
Q
To see near, how does the eye accomodate?
A
- Ciliary muscle contracts
- Suspensory ligament lax
- lends becomes globular (thickens)
10
Q
What is emmetropia?
A
Normal vision
11
Q
What is myopia and where is the focal point?
A
near sightedness. focal point is in front of the eye
can see near, focus light in front of the retina,
12
Q
What is hyperopia and where is the focal point?
A
far-sightedness and the focal pt is in back of the retina
can see far, light focuses behind the retina, cant see near
13
Q
How do glassses/contacts help you see?
A
glasses/contacts changes the angle of light so it reaches the retina
14
Q
Projections of the visual field/image onto the retina are ____
A
inverted (flipped upside down and backwards)
15
Q
What you are looking at in space
A
Visual field
16
Q
What’s projected onto the retina
A
retinal field
17
Q
All information from the right visual field will end up on the ____ portion of the brain.
A
left
18
Q
How does info from your right visal field end up on the left side of your brain?
A
- Info projects onto temporal regions of LEFT retina and nasal region of Right retina
- all info that projects to temporal stays ipsilateral. Info projected to nasal retina will cross to contralateral side
- So then its sents up left optic tract and left side of brain for processing
19
Q
Given that each eye receives information from either visual field, fibers cross at the ____ to get information from the visual field to its respective cortical region.
A
optic chiasm
20
Q
What are the two types of photoreceptors of the retina?
A
Rods and cones
21
Q
What are the two types of photoreceptors of the retina?
A
Rods and cones
22
Q
Where are rods located?
A
every where else in the retina (except optic disk)
23
Q
Where are cones located?
A
Macula/Fovea
24
Q
What are the 4 retinal neurons?
A
- Horizontal cells
- Bipolar cell
- Amacrine cell
- Ganglion cell
1 and 2 produce graded potentials and sends excitatroy signals to 3 and 4 which produce action potentials
25
Briefly explain how light reaches the retina?
1. Light enters the superficial retina, passes through cell bodies, and travels towards the back in order to reach photosensitive cells (rods and cones).
2. Action potential allows photoreceptor signaling to be sent back up towards the superficial retina where they can then be guided to the optic nerve and CNS.
26
What are rods highly sensitive to?
Low levels of light
## Footnote
not sensitive to color
27
What protein do rods have and do they have a large or small number of disks?
Opsin=rhodopsin
large number of disks
## Footnote
Rods have far larger areas of photoreceptor disks to make them highly sensitive to light.
28
What are cones sensitive to?
Cones are sensitive to colors
29
What protein do cones have and do they have a large or small number of disks?
Many (around 3) different opsins
smaller number of disks
## Footnote
diff opsons are responsible for detectong diff wavelenghts that gives us diff colors
30
What is the fxn of pigment epithelium?
It is a "backwards" organization of the retinal later due to the need for constant recycling of photoreceptor protiens (opsins) and disks
## Footnote
rods and cones photoreceptors are embedded here and recycles
31
Why do we need to recycle photoreceptor proteins and what is required?
| on exam
Need to be constantly synthesizing new protiens so tha we stay sensitive to light especially rods (low light conditions). We need VITAMIN A retinol , this maintains rods and rhodopsin signaliong
## Footnote
50-85 of total body retinol is stored in liver
32
What is scotopic vision?
Only rods are being used
## Footnote
like an on/off switch, no wavelength to tell you color
33
What is mesopic vision?
Rods and cones are being used
## Footnote
you can see color
34
What is photopic vision?
only cones are being used (rodes are sat with light)
## Footnote
rods are sat with light so much that rods arent firing anymore, and we use cones
35
Which type of vision has the best acuity?
Photopic vision
## Footnote
bc cone and color info
36
Light sensitivity depend on ____ and ____.
receptive field size and intensity
37
Rods are usually activated at what wavelength of light?
400-600nm
38
What is trichromat?
This is normal vision; you contain all 3 cones subtype
## Footnote
have all 3 opsins
39
What is protanopia?
This is a type of colorblindness where you loose the cone subtype responsible for RED wavelengths
## Footnote
2/3 opsins, missing longest=red wl of light
pRo=Red
40
What is deuteranopia?
This is a type of colorblindness where you loose the cone subtype responsible for GREEN wavelengths
## Footnote
2/3 opsins, missing middle=green wl of light
41
Activation of this alters a membrane current that controls photoreceptor transmitter release
Rhodopsin
42
In the abscence of light, explain what happens to photoreceptor rhodopsin and its relation to glutamate
1. Rhodopsin is INACTIVE
2. Na+ channels opens and influx
3. Cell is DEPOLARIZED
4. HIGH rate of glutamate is released constantly
## Footnote
cones have the SAME signaling using different opsins.
43
With light, explain what happens to photoreceptor rhodopsin and its relation to glutamate
1. Rhodopsin is ACTIVE
2. Na+ channels CLOSED
3. Cell is HYPERPOL
4. Low rate of glutamate release
| basically no glutamate released
## Footnote
cones have the SAME signaling using different opsins.
44
Explain briefly vertical info flow
1. Rods and cones release glut
2. This is inhibitors or excitatory depending in the glut receptors expresed on the bipolar cell
3. **Bipolar cells** release glutamate which is excitatory for **ganglion cells**
## Footnote
ganglion cells=retinol ganglion cells (RGC)
45
Explain vertical info flow for ON center receptor field (light comes in)
Light stimulation causes
1.HYPERPOL of photoreceptor, and no glutamate is release
2. INCR DEPOL of ON center bipolar cell , so mGLU is activated
3. INCR glutamamte release from on bipolar cells
4. Incr gangliom cell firing rate
46
Explain vertical info flow for OFF center receptor field (light comes in)
Light stimulation causes
1. HYPERPOL of photoreceptor, and no glutamate is release
2. DECR dep of OFF center bipolar cell , so NMDA rec is INHIBITED (b/c hyperpol)
3. DECR glutamamte release from off bipolar cells
4. DECR ganglion cell firing rate
47
With light mention if the following are activated or inhibited?
A. On-center bipolar cell (mGlu)
B. Off-center bipolar cell (NMDA)
A. On-center bipolar cell (mGlu): ACTIVATED
B. Off-center bipolar cell (NMDA): INHIBITED
48
With NO light mention if the following are activated or inhibited.
A. On-center bipolar cell (mGlu)
B. Off-center bipolar cell (NMDA)
A. On-center bipolar cell (mGlu): INHIBITED
B. Off-center bipolar cell (NMDA): ACTIVATED
49
What variables contribute to mapping center-surrond receptive field of the retina?
* Duration of spot illumination
* Size of spot illumination
* Background light intensitiy of both center and surround area
| center compated to peripheral environment
## Footnote
ex:a grey spot next to white looks much darker than the same grey spot next to black
50
What is 20/20 vision?
At 20 feet, a human with nominal eye performance is able to separate lines for image recognition
## Footnote
20/40 vision, at 20 feet a human is able to sep line for image recognition that a perosn with nominal performance can resole at 40 feet
51
What are the 2 types of synaptic transmission in the retina?
chemical and electrical
## Footnote
need electrical to identify things moving very quickly
52
What are the two cells involved in lateral information flow and explain their fxn
1. Horizontal cells: release GABA (inhibitory) and form gap junctions.
2. Amacrine cells: release GABA, glycine, dopamine (inhibitory) and form gap junctions
53
What is lateral inhibition essential for?
Essential for identifying shapes (edges) and detecting motion
54
Horizontal cells always have a ____ output via release of ____.
inhibitory, GABA
55
What are horizontal cells connected to?
Connected laterally to photoreceptor cells, and they suppress vertical information flow in adjacent pathways
56
Explain how horizontal cells play a role in lateral inhibition in this case, for an ON-center receptive field, with NO surround light stimulation
1. There is a dark surround, this inhibits center cone via GABA
2. Less glutamate release and stimulation of the one-center bipolar cells,
3. Incr ganglion cell firing
57
Dark stimulated surround ____ on enter response
enhances/incr
58
Explain how horizontal cells play a role in lateral inhibition in this case, for an ON-center receptive field, WITH surround light stimulation
1. Surround photoreceptor is activated and therefore hyperpol with decr release of glut
2. Reduction of glut reduces release of GABA from horizontal cells
3. Reduction of gaba inhibition causes dep of photoreceptors in the center and incr release of glut
4. Incr release of Glu from photoreceptor causes a decr in ON center ganglion cells firing
59
Light stimulated surround ____ on center response
inhibits/decr
60
Lateral inhibition relies on what?
Gap jxns: provides cell-cell coupling
61
What does lateral inhibition promote and amplify?
Lateral inhibitions promotes contrast enhancement and amplifies edge detection of the retina
## Footnote
detect edges with shape
62
For information flow to the brain, the visual scene is encoded by the firing patterns of ____ ____ ____ , which is further processed in the ____ ____ by the way of the ____ ____.
retinal ganglion cells
visual cortex
optic nerve
63
What are the subtypes of retinal neurons?
1. Photoreceptors
2. Horizontal cells
3. Bipolar cells
4.Amacrine cells
5.Ganglion cells
64
What is the lens retinal prosthesis?
A computer chip embedded in lens that mimic retina
