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NAB > Visual > Flashcards

Visual Flashcards

1
Q

What happens during accomodation?

A

Ciliary muscle fibres contracted, suspensory ligs relaxed, lens thick

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2
Q

What does chromophore isomerise from and to?

A

11-cis to all-trans retinal

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3
Q

What does transducin activate?

A

Phosphodiesterase

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4
Q

What does Ca2+ inhibit?

A

Guanyly cyclase

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5
Q

Why does Ca2+ fall in light?

A

cGMP opens CNG channel

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6
Q

What is red dichromacy called?

A

Deuteranopia

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7
Q

What is green dichromacy called?

A

Protanopia

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8
Q

What is found in the outer nuclear layer?

A

Photoreceptor nuclei

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9
Q

What is found in the inner nuclear layer?

A

Bipolar horizontal and amacrine cells

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10
Q

What is invaginated within a cone pedicle?

A

Bipolar and horizontal

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11
Q

Layers of eye from the vitreous?

A

Inner limiting membrane, nerve fibres, ganglion cell bodies, inner plexiform, bipolar cells, outer plexiform, photoreceptor cell bodies, outer limiting membrane, rods and cones, pigment cells

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12
Q

What is the rod photoreceptor terminal called?

A

Rod spherule

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13
Q

Which is parvocellular?

A

For sustained input, colour-encoded, slow conduction

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14
Q

Which is magnocellular?

A

For rapid changes/motion, non-chromatic, high sensitivity, fast conduction, wide area, convergent

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15
Q

Which neurotransmitters do amacrine cells use?

A

All

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16
Q

Projections of retinal ganglion cells?

A

LGN, pretectum, SCN, superior colliculus

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17
Q

Where is right LGN input from?

A

Left temporal and right nasal

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18
Q

Where is left LGN input from?

A

Right temporal and left nasal

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19
Q

What is disparity?

A

Difference in angle at the two eyes

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20
Q

Where are illusory contours detected?

A

Cells in V2

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21
Q

Dorsal where pathway?

A

Magno > 4Calpha > 4B > thick > V3 for dynamic form

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22
Q

What does dorsal where pathway detect?

A

Visual flow

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23
Q

Other dorsal where pathway?

A

Magnocellular > LGN > V1 complex cells > V2 thick stripe > V5 or V5a

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24
Q

Parvocellular what pathway?

A

Parvocellular > LGN > V1 blob > V2 thin stripe > V4 colour

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25
Q

Parvocellular/magnocellular what pathway?

A

LGN > V1 interblob > V2 interstripe > V4 form > infratemporal lobe (faces)

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26
Q

Which is the sign inverting synapse?

A

Cone depolarised to on centre bipolar cell

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27
Q

Which do horizontal cells inhibit when when they depolarise?

A

Cone

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28
Q

What happens when bipolar cell hyperpolarises?

A

Ganglion cell firing decreases

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29
Q

What is illuminance?

A

Intensity of incident light

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30
Q

What is luminance?

A

Intensity of reflected light

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31
Q

What is Weber’s law?

A

R = change in I / I + Io

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32
Q

What is threshold contrast?

A

k = change in I / I

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33
Q

What is bleaching desensitisation?

A

Persistent excitation of phototransduction so reduced cytoplasmic Ca2+

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34
Q

What is bleaching adaptation?

A

decrease in sensitivity following very bright light

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35
Q

What is light adaptation?

A

Responds to the mean as illuminance increases so black always has lower luminace at any illuminance. A reversible change in sensitivity when steady intensity is altered.

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36
Q

What happens to spontaneous Rh* rate in the warm?

A

Lower absolute threshold

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37
Q

Which cells does dopamine reduce coupling between?

A

AII amacrine cells

38
Q

Which signal flow does dopamine amacrine enable?

A

Via AII “rod” amacrine

39
Q

What increases coupling in dark adaptation?

A

Dopaminergic A18 amacrine cells

40
Q

How does dopamine affect gap junctions?

A

Decouples

41
Q

Which kind of wavelength stimulates rods?

A

Short

42
Q

What is flicker fusion frequency like in rods in the dark?

A

Low

43
Q

Why is flicker fusion frequency better in the light?

A

Both rods and cones used

44
Q

What is ouput of MT region?

A

Eye movements

45
Q

What is input to MT and MST?

A

Movement - flow field (magnocellular)

46
Q

What is the corneal stroma made of?

A

Parallel collagen fibres

47
Q

What is the lens made of?

A

Crystallins

48
Q

What does the rod outer segment contain?

A

Internalised discs

49
Q

What regenerates rhodopsin?

A

Isomerohydrolase

50
Q

What is retinitis pigmentosa?

A

loss of peripheral rod vision

51
Q

What carries the dark current in the inner segment?

A

K+ out

52
Q

What carries the dark current in the outer segment?

A

Na and Ca in

53
Q

When are Ca levels high and when are they low?

A

High in the dark

54
Q

What three things does calcium do?

A

R* activation, affects cGMP affinity, inhibits GC

55
Q

Which channel is cGMP gated and closes?

A

NA

56
Q

Where are the synaptic triads?

A

Cone pedicle

57
Q

Which art of the cone establishes the receptive field of the bipolar cell?

A

Pedicle

58
Q

Which LGN layers are parvocellular?

A

Four dorsal

59
Q

Which LGN layers are magnocellular?

A

Two ventral

60
Q

Other name for V1?

A

Striate cortex

61
Q

How much of V1 is dedicated to the macula?

A

50%

62
Q

Name of layer 4?

A

Stria of Gennari

63
Q

Where do parvo and magnocellular terminate?

A

4C (beta for parvo, alpha for magno)

64
Q

What do V1 cells respond best to?

A

Bars of light

65
Q

Which layers are simple cells found in?

A

4 and 6

66
Q

Which layers are complex cells found in?

A

2,3,5

67
Q

What do V5/5a lesions cause?

A

Movement agnosia or akinetopsia (can’t see motion)

68
Q

Where are the cells which detect visual flow?

A

V5

69
Q

Where does V5 go to?

A

Superior colliculus

70
Q

Which areas do blob cell occur in?

A

Output layers 2 and 3 but not 4

71
Q

Which animals are tetrachromats?

A

Birds and reptiles

72
Q

Which pigments are in bird eyes?

A

Carotenoids

73
Q

Who are dichromats?

A

Dogs

74
Q

How is the signal representing luminance generate?

A

Responses of medium and long wavelength cones are summed together

75
Q

What is the signal in the blue yellow opponent channel?

A

Differences between responses of the short wavelength cones and the sum of the medium and long wavelength cone responses

76
Q

By which pathway do blue-yellow opponent cells pass to LGN?

A

Koniocellular

77
Q

Where are the double opponent receptive cells?

A

V1

78
Q

What do the red-green cones exhibiting centre surround antagonism signal?

A

Luminace

79
Q

What are single opponent cells ambiguous for? What is used instead

A

Colour and brightness, double opponent

80
Q

Where do double opponent cells project to?

A

V4 in area 18

81
Q

Which cells respond best to coloured edges?

A

Subset of simple and complex cells in the interblob region

82
Q

Where are the cells which mediate colour constancy?

A

Area V4

83
Q

What does the threshold contrast encode?

A

Difference in intensity

84
Q

What sets the absolute threshold?

A

The dark light

85
Q

How does heat affect absolute threshold?

A

Lowers it

86
Q

Which cells exhibit bleach-induce fluctuations?

A

Individual rods

87
Q

What does dopamine do to coupling between AII amacrine cells?

A

Reduces

88
Q

What is bleaching desensitization?

A

Persistent excitation of phototransduction

89
Q

Which range are AII amacrine cells activated in?

A

Scotopic

90
Q

What increase coupling in dark adaptation?

A

Dopaminergic A18 amacrine cells

91
Q

What does dopamine released in the light do?

A

Decouples gap junctions

92
Q

Why is flicker frequency better int he light?

A

Cones used

NAB (10 decks)

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