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Neuroscience > 09a: Vision > Flashcards

09a: Vision Flashcards

1
Q

List the various segments of photoreceptor and function/characteristic of each segment.

A
  1. Outer (photosensitive)
  2. Inner (contains mitochondria and nucleus)
  3. Synaptic ending (communicates with retina)
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2
Q

T/F: Rods and cones are identical in structure, despite difference in function.

A

False - outer segments vary

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3
Q

(Rods/cones) are very sensitive to light, capable of responding to single photon.

A

Rods

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4
Q

Scotopic vision is (day/night/color) vision and carried out most effectively by (rods/cones).

A

Night; rods

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5
Q

Photopic vision is (day/night/color) vision and carried out most effectively by (rods/cones).

A

Day; cones

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6
Q

(Rods/cones) contains rhodopsin, which is comprised of: (star the light-catching part)

A

Both;

  1. Opsin (integral membrane protein)
  2. 11-cis retinal (chromophore)*
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7
Q

To increase packing density of (X), (rods/cones) have:

A

X = rhodopsin

Rods: membranous disks on outer segment
Cones: invaginations/sacs on outer segment

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8
Q

Which key part of rods/cones is derivative of Vitamin (X).

A

X = A

11-cis retinal (chromophore of rhodopsin)

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9
Q

Absorption of (X) number of photon(s) isomerizes (Y) to (Z).

A 
X = 1
Y = 11-cis retinal
Z = all-trans retinal
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10
Q

When is rhodopsin “bleached”?

A

All-trans retinal detaches from opsin

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11
Q

T/F: when rhodopsin is bleached, it can no longer absorb visible light.

A

True

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12
Q

First step of phototransduction cascade.

A

Activated rhodopsin (all-trans retinal) activates transducin (G-protein)

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13
Q

Transducin is a(n) (X) which, when activated by (Y), leads to:

A 
X = G-protein
Y = Rhodopsin (active)

Activation of PDE

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14
Q

Transducin activates (X), which causes (Y), thus (increasing/decreasing) (Z).

A

X = PDE
Y = rapid hydrolysis of cytosolic cGMP
Decreasing;
Z = cGMP levels

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15
Q

In darkness, (low/high) levels of (X) keeps constant (influx/efflux) of (Y) ion(s) in (inner/outer) segment of photoreceptors.

A 
High; 
X = cGMP;
Influx of (Y=) Na and Ca in outer segment;
Efflux of (Y=) K from inner segment
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16
Q

Typical resting Vm of photoreceptor.

A

-35 mV

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17
Q

The photoreceptor is more (de/hyper)-polarized than typical neuron, which keeps (X) channels (open/closed) in synaptic ending. This leads to continuous (Y).

A

Depolarized;
X = Ca
Open
Y = release of glutamate

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18
Q

In (presence/absence) of light, there is constant release of which AA?

A

Absence;

Glutamate

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19
Q

(Rods/cones) generate action potentials.

A

Neither! Photoreceptors don’t generate action potentials

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20
Q

(Rods/cones) generate receptor potential that’s graded in response to (X).

A

Both;

X = intensity of light

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21
Q

The signal from photoreceptors first passes to (X) cells and then to (Y) cells.

A 
X = bipolar
Y = retinal ganglion
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22
Q

List the classes of bipolar cells.

A
  1. H-bipolars (off-center)

2. D-bipolars (on-center)

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23
Q

H-bipolar cells express (X) receptors, so light causes them to (de/hyper)-polarize.

A

X = ionotropic glutamate

Hyperpolarize

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24
Q

D-bipolar cells express (X) receptors, so light causes them to (de/hyper)-polarize.

A

X = metabotropic glutamate

Depolarize

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25
Q

(D/H)-bipolar cells generate action potential.

A

Neither!

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26
Q

The reason (photoreceptors/bipolars/retinal ganglions) don’t generate AP is because distance of propagation of electrical signals is small enough for efficient electronic spread.

A

Bipolar cells

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27
Q

(H/D)-bipolar cells establish an excitatory synapse with subsequent (X) cells.

A

H: (X=) off-center retinal ganglion cells

D: (X=) on-center retinal ganglion cells

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28
Q

(On/off)-center retinal ganglion cells generate action potentials.

A

Both

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29
Q

Light causes (X) response in H-bipolar cells and then (Y) response in (Z) cells.

A 
X = hyperpolarization
Y = inhibition of action potentials 
Z = off-center retinal ganglion
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30
Q

Light causes (X) response in D-bipolar cells and then (Y) response in (Z) cells.

A 
X = depolarization
Y = activation of AP
Z = on-center retinal ganglion
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31
Q

The optic nerve is formed from axons of (X) cells.

A

X = retinal ganglion

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32
Q

Which cells in retina are involved in lateral interactions?

A
  1. Horizontal cells

2. Amacrine cells

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33
Q

Horizontal cells in retina present extensive (Y) processes that intermingle with (Z).

A 
Y = dendritic
Z = processes of photoreceptors and bipolar cells
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34
Q

Stimulation of horizontal cells causes them to (stimulate/inhibit) neighboring synapses.

A

Inhibit

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35
Q

Amacrine cells in retina present extensive (Y) processes that intermingle with (Z).

A 
Y = dendritic
Y = processes of bipolar cells and ganglion cells
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36
Q

Cones contain the same (photopigment/chromophore), but three different forms of (photopigments/chromophores), linked to (same/different) (X).

A

Chromophore;
Photopigments

X = the same chromophore

37
Q

Blue cones preferentially absorb light in (X) range wavelength.

A

X = short (peak 420 nm)

38
Q

Green cones preferentially absorb light in (X) range wavelength.

A

X = medium (peak 530 nm)

39
Q

Red cones preferentially absorb light in (X) range wavelength.

A

X = long (peak 560 nm)

40
Q

(Rods/cones) have more direct path to Ganglion cells.

A

Cones

41
Q

(Rods/cones) have higher degree of convergence and, thus, (high/low) spatial resolution.

A

Rods; low

42
Q

Receptive field center receives (direct/indirect) input from:

A

Direct; photoreceptor

43
Q

Receptive field surround receives (direct/indirect) input from:

A

Indirect; horizontal cells

44
Q

Response to light in field center is (same/opposite) of response to light in the surround.

A

Opposite

45
Q

On-center (X) cells respond to (light/dark) in (center/surround) of receptive field.

A

X = retinal ganglion;
Light;
Center

46
Q

Off-center (X) cells respond to (light/dark) in (center/surround) of receptive field.

A

X = retinal ganglion;
Dark;
Center

47
Q

(On/off)-center ganglion cells are very responsive to changes in illumination that include both center & surround.

A

Neither! Responsive to changes in contrast between center/surround

48
Q

At t0, the center and surround of receptive field are same shade of grey. At t1, the center goes a shade of darker grey. How do on/off-center retinal ganglion cells respond?

A

On-center: less AP fired

Off-center: more AP fired

49
Q

At t0, the center and surround of receptive field are same shade of grey. At t1, the center goes a shade of darker grey. How do on/off-center (or D/H-) bipolar cells respond?

A

D (on-center): hyperpolarize

H (off-center): depolarize

50
Q

At t0, the center is a shade of darker grey than the surround. At t1, the center turns the same shade of grey as the surround. How do on/off-center retinal ganglion cells respond?

A

On-center: more AP fired

Off-center: less AP fired

51
Q

At t0, the center is a shade of darker grey than the surround. At t1, the center turns the same shade of grey as the surround. How do on/off-center (or D/H-) bipolar cells respond?

A

D (on-center): depolarize

H (off-center): hyperpolarize

52
Q

In dark adaptation of retina, (X) cells (increase/decrease) their sensitivity.

A

X = photoreceptor;

Increase

53
Q

In light adaptation of retina, (X) cells (increase/decrease) their sensitivity.

A

X = photoreceptor;

Decrease

54
Q

Light adaptation occurs via (X) feedback since bright light effect of (increase/decrease) in (X) will cause (increase/decrease) production of (Y).

A

X = Ca;
Decrease (in cytoplasmic Ca);
Increase;
Y = cGMP

55
Q

Light adaptation: (high/low) cytoplasmic (X) causes (increase/decrease) affinity of (Y) to (Z) channels.

A 
Low;
X = Ca;
Increase;
Y = cGMP
Z = Na/Ca channels
56
Q

Each retina’s visual field can be divided into (X) and (Y) divisions.

A 
X = temporal
Y = nasal
57
Q

Left eye receives information about (left/right) visual field.

A

Both!

58
Q

The temporal division of the right retina receives information from which visual field?

A

Left visual field

59
Q

The nasal division of the left retina receives information from which visual field?

A

Left visual field

60
Q

The nasal division of the right retina receives information from which visual field?

A

Right visual field

61
Q

Right optic nerve contains information from (right/left) eye and (right/left) visual fields.

A

Right; both

62
Q

At the optic chasm, (X) retinal fibers decussate, but (Y) retinal fibers do not.

A 
X = nasal;
Y = temporal
63
Q

Right optic tract fibers contain information from (right/left) eye and (right/left) visual fields.

A

Both eyes;

Left (contralateral) visual field

64
Q

Info from right visual field will travel in (right/left) optic nerve and (right/left) optic tract.

A

Both optic nerves;

Left optic tract

65
Q

Damage to region of optic chasm would result in vision loss from which part of

A

Nasal retina

66
Q

Vision pathway: At (X), a small fraction of (Y) fibers will synapse in (Z) to provide light/dark information for regulating circadian rhythms.

A 
X = optic chiasm;
Y = retinal ganglion cell
Z = suprachiasmatic nucleus (of hypothalamus)
67
Q

Majority of fibers in optic tract will synapse on cells in:

A

LGN (thalamus)

68
Q

Minority of fibers in optic tract will pass through/around (X) to synapse on:

A

X = LGN;

  1. Pretectum nuclei OR
  2. Superior colliculus nuclei
69
Q

Visual input to pretectum is for (conscious/unconscious) (X).

A

Unconscious;

X = pupillary reflex and lens control

70
Q

Visual input to superior colliculus is for (conscious/unconscious) (X).

A

Unconscious;

X = orienting movement of head/eyes

71
Q

Our conscious perception of visual world: visual input from retinal ganglion cell projection to (X), then (Y).

A 
X = LGN
Y = primary visual cortex
72
Q

Right LGN receives information from (right/left) eye and (right/left) visual field.

A

Both eyes;

Left visual field

73
Q

LGN has (X) number of layers that can be divided into which group(s)?

A

X = 6

  1. Magnocellular (inner two layers)
  2. Parvocellular (outer four layers)
74
Q

T/F: LGN cells have center/surround excitatory/inhibitory organization.

A

True

75
Q

(X) cells of LGN have large cell bodies and (small/large) receptive fields. (Y) cells of LGN have small cell bodies and (small/large) receptive fields.

A

X = M (magnocellular)
Large;
Y = P (parvocellular)
Small

76
Q

(X) cells of LGN have fast and transient responses. This contributes to their high sensitivity to:

A

X = M

Contrast

77
Q

(X) cells of LGN have slow conduction velocity and (low/high) sensitivity to changes in contrast.

A

X = P

Low

78
Q

(X) cells of LGN carry more information about details than (Y) cells of LGN.

A 
X = P
Y = M
79
Q

(X) cells of LGN carry information about color.

A

X = P (only)

80
Q

(X) cells of LGN provide info with high temporal resolution.

A

X = M

81
Q

(X) cells of LGN provide info with high spatial resolution.

A

X = P

82
Q

Which LGN layers contain maps of contralateral visual field? And ipsilateral visual field?

A

Each layer contains complete map of CONTRALATERAL visual field

83
Q

Which LGN layers receives input from contralateral eye? And ipsilateral eye?

A

Ipsilateral: 5, 3, 2
Contralateral: 6, 4, 1

84
Q

Main projection from LGN is to:

A

Striate cortex (aka V1 or primary visual cortex)

85
Q

The striate cortex has (X) number of layers and projects to:

A

X = 6;

V2-V5 and other extrastriate visual areas

86
Q

There’s greater representation of (X) retina regions than (Y) retina regions in striate cortex.

A 
X = fovea/parafoveal 
Y = peripheral
87
Q

Visual input from the L/R eyes begins to be (separated/combined) in the cells of (X).

A

Combined;

X = striate cortex

88
Q

(LGN/striate cortex) is organized into groups of columns, formally called (X) columns. Cells in adjacent columns have difference in:

A 
Striate cortex;
X = orientation columns
Orientation preference (by 10o)

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