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Neurosciences > Exam2Lec4Vision:RetinalProcessing > Flashcards

Exam2Lec4Vision:RetinalProcessing Flashcards

1
Q

What is the region of high visual acuity in the eye?

A

macula/fovea

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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

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3
Q

What is the vascular supply of the eye?

A

branch of opthalmic artery and branch of opthalmic vein

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4
Q

Most of our vision is ____

A

binocular

this is central vision (both eyes)

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5
Q

Most of our peripheral vision is____

A

monocular

one eye

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6
Q

Where is light absorbed?

A

retina

light perception begins at retina

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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

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8
Q

To see far, what how does the eye accomodate?

A
  1. Ciliary muscle relaxes
  2. suspensory ligament taut
  3. lends flattens/thins
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9
Q

To see near, how does the eye accomodate?

A
  1. Ciliary muscle contracts
  2. Suspensory ligament lax
  3. lends becomes globular (thickens)
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10
Q

What is emmetropia?

A

Normal vision

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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,

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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

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13
Q

How do glassses/contacts help you see?

A

glasses/contacts changes the angle of light so it reaches the retina

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14
Q

Projections of the visual field/image onto the retina are ____

A

inverted (flipped upside down and backwards)

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15
Q

What you are looking at in space

A

Visual field

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16
Q

What’s projected onto the retina

A

retinal field

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17
Q

All information from the right visual field will end up on the ____ portion of the brain.

A

left

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18
Q

How does info from your right visal field end up on the left side of your brain?

A
  1. Info projects onto temporal regions of LEFT retina and nasal region of Right retina
  2. all info that projects to temporal stays ipsilateral. Info projected to nasal retina will cross to contralateral side
  3. So then its sents up left optic tract and left side of brain for processing
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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

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20
Q

What are the two types of photoreceptors of the retina?

A

Rods and cones

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21
Q

What are the two types of photoreceptors of the retina?

A

Rods and cones

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22
Q

Where are rods located?

A

every where else in the retina (except optic disk)

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23
Q

Where are cones located?

A

Macula/Fovea

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24
Q

What are the 4 retinal neurons?

A
  1. Horizontal cells
  2. Bipolar cell
  3. Amacrine cell
  4. Ganglion cell

1 and 2 produce graded potentials and sends excitatroy signals to 3 and 4 which produce action potentials

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25
Q

Briefly explain how light reaches the retina?

A
  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.
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26
Q

What are rods highly sensitive to?

A

Low levels of light

not sensitive to color

27
Q

What protein do rods have and do they have a large or small number of disks?

A

Opsin=rhodopsin
large number of disks

Rods have far larger areas of photoreceptor disks to make them highly sensitive to light.

28
Q

What are cones sensitive to?

A

Cones are sensitive to colors

29
Q

What protein do cones have and do they have a large or small number of disks?

A

Many (around 3) different opsins
smaller number of disks

diff opsons are responsible for detectong diff wavelenghts that gives us diff colors

30
Q

What is the fxn of pigment epithelium?

A

It is a “backwards” organization of the retinal later due to the need for constant recycling of photoreceptor protiens (opsins) and disks

rods and cones photoreceptors are embedded here and recycles

31
Q

Why do we need to recycle photoreceptor proteins and what is required?

on exam

A

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

50-85 of total body retinol is stored in liver

32
Q

What is scotopic vision?

A

Only rods are being used

like an on/off switch, no wavelength to tell you color

33
Q

What is mesopic vision?

A

Rods and cones are being used

you can see color

34
Q

What is photopic vision?

A

only cones are being used (rodes are sat with light)

rods are sat with light so much that rods arent firing anymore, and we use cones

35
Q

Which type of vision has the best acuity?

A

Photopic vision

bc cone and color info

36
Q

Light sensitivity depend on ____ and ____.

A

receptive field size and intensity

37
Q

Rods are usually activated at what wavelength of light?

A

400-600nm

38
Q

What is trichromat?

A

This is normal vision; you contain all 3 cones subtype

have all 3 opsins

39
Q

What is protanopia?

A

This is a type of colorblindness where you loose the cone subtype responsible for RED wavelengths

2/3 opsins, missing longest=red wl of light
pRo=Red

40
Q

What is deuteranopia?

A

This is a type of colorblindness where you loose the cone subtype responsible for GREEN wavelengths

2/3 opsins, missing middle=green wl of light

41
Q

Activation of this alters a membrane current that controls photoreceptor transmitter release

A

Rhodopsin

42
Q

In the abscence of light, explain what happens to photoreceptor rhodopsin and its relation to glutamate

A
  1. Rhodopsin is INACTIVE
  2. Na+ channels opens and influx
  3. Cell is DEPOLARIZED
  4. HIGH rate of glutamate is released constantly

cones have the SAME signaling using different opsins.

43
Q

With light, explain what happens to photoreceptor rhodopsin and its relation to glutamate

A
  1. Rhodopsin is ACTIVE
  2. Na+ channels CLOSED
  3. Cell is HYPERPOL
  4. Low rate of glutamate release

basically no glutamate released

cones have the SAME signaling using different opsins.

44
Q

Explain briefly vertical info flow

A
  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

ganglion cells=retinol ganglion cells (RGC)

45
Q

Explain vertical info flow for ON center receptor field (light comes in)

A

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
Q

Explain vertical info flow for OFF center receptor field (light comes in)

A

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
Q

With light mention if the following are activated or inhibited?
A. On-center bipolar cell (mGlu)
B. Off-center bipolar cell (NMDA)

A

A. On-center bipolar cell (mGlu): ACTIVATED
B. Off-center bipolar cell (NMDA): INHIBITED

48
Q

With NO light mention if the following are activated or inhibited.
A. On-center bipolar cell (mGlu)
B. Off-center bipolar cell (NMDA)

A

A. On-center bipolar cell (mGlu): INHIBITED
B. Off-center bipolar cell (NMDA): ACTIVATED

49
Q

What variables contribute to mapping center-surrond receptive field of the retina?

A
  • Duration of spot illumination
  • Size of spot illumination
  • Background light intensitiy of both center and surround area

center compated to peripheral environment

ex:a grey spot next to white looks much darker than the same grey spot next to black

50
Q

What is 20/20 vision?

A

At 20 feet, a human with nominal eye performance is able to separate lines for image recognition

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
Q

What are the 2 types of synaptic transmission in the retina?

A

chemical and electrical

need electrical to identify things moving very quickly

52
Q

What are the two cells involved in lateral information flow and explain their fxn

A
  1. Horizontal cells: release GABA (inhibitory) and form gap junctions.
  2. Amacrine cells: release GABA, glycine, dopamine (inhibitory) and form gap junctions
53
Q

What is lateral inhibition essential for?

A

Essential for identifying shapes (edges) and detecting motion

54
Q

Horizontal cells always have a ____ output via release of ____.

A

inhibitory, GABA

55
Q

What are horizontal cells connected to?

A

Connected laterally to photoreceptor cells, and they suppress vertical information flow in adjacent pathways

56
Q

Explain how horizontal cells play a role in lateral inhibition in this case, for an ON-center receptive field, with NO surround light stimulation

A
  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
Q

Dark stimulated surround ____ on enter response

A

enhances/incr

58
Q

Explain how horizontal cells play a role in lateral inhibition in this case, for an ON-center receptive field, WITH surround light stimulation

A
  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
Q

Light stimulated surround ____ on center response

A

inhibits/decr

60
Q

Lateral inhibition relies on what?

A

Gap jxns: provides cell-cell coupling

61
Q

What does lateral inhibition promote and amplify?

A

Lateral inhibitions promotes contrast enhancement and amplifies edge detection of the retina

detect edges with shape

62
Q

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 ____ ____.

A

retinal ganglion cells
visual cortex
optic nerve

63
Q

What are the subtypes of retinal neurons?

A
  1. Photoreceptors
  2. Horizontal cells
  3. Bipolar cells
    4.Amacrine cells
    5.Ganglion cells
64
Q

What is the lens retinal prosthesis?

A

A computer chip embedded in lens that mimic retina

Neurosciences (28 decks)

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