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Perception block 11 > Fucntional Retina > Flashcards

Fucntional Retina Flashcards

1
Q

Ganglion cells in the fovea

A

They are directed away from the fovea

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2
Q

Is the retina just a reciever or does it receive and analyze

A

Analyzes too

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3
Q

Ganglion cells: action or graded potential?

A

Action

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4
Q

Electrophysiology of ganglion cells

A
  • Fovea aligned with point on screen
  • Micoelecrtode placed in extracellular fluid next to ganglion
  • Action potentials read
  • Spot of light elicits response from cell
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5
Q

Spoanteous activity

A

Cells spontaneously generates action potentials

-maintained discharge

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6
Q

A stimulus in the receptive field and the firing rate of the neuron

A

Will either increase or decrease the firing rate of the neuron, depends on location

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7
Q

Primary input to the ganglion cells

A

Photoreceptors

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8
Q

A small light located within the center of the this receptive field does what

A

Causes an increases in the frequency of action potentials

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9
Q

Small light positioned int he surround of the receptirvefield

A

Produced a reduction in the frequency of action potentials

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10
Q

If the experiment is repeated with a larger spot of light, there is an _____in the frequency of action potentials due to spatial summation that occurs within the receptive fields center

A

Increase

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11
Q

If light covers the center and the surround: GC response to a stimulus like this is _______ as if there was no stimulus

A

About the same

-spatially antagonistic ganglion cells do not respond well to diffuse illumination

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12
Q

Spatially antagonistic ganglion cells and diffuse illumination

A

Do not respond well to diffuse illumination

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13
Q

Ganglion cells and sine wave grating (bars)

A

Strong stimulus for ganglion

  • bright bar falls on excitatory center: increased frequency of action potentials
  • dark bars fall on inhibitory surround: also increases the frequency of action potentials
  • spatial grating vigorously excites cell
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14
Q

Spatial grating and GC

A

Vigorously excites the cell

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15
Q

Receptive field GC graph

A

As spot of light increases, action potentials increase. When you reach C (whol width of center) action potentials actually decrease at this point with larger stimulus
-eventually a point is reached where further increases int he stimulus diamter have no effect on the cells response

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16
Q

How does a photoreceptors respond to light

A

Hyperpolarizes

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17
Q

Horizaontal cells respond to light

A

Hyperpolarizes

-has an input from more than one photoreceptor

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18
Q

Off-center, on-surround bipolar cell with the annulus of light

A

Becomes more negative

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19
Q

Off center and on surround amacrine cell

A

Action potentials

-first cell int he sequence where we see an action potential response

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20
Q

Ganglion cell off center

A

Action potential in the dark, hyperpolarizes in the dark

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21
Q

Specialized sensory receptors that contain photosensitive epigment.

A

Photoreceptors

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22
Q

Light quanta int he photoreceptors

A

Converted into electrical activity

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23
Q

Photoreceptors are slightly _______

A

Depolarized

  • RMP: -50mV
  • typical neuron RMP: -70mV
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24
Q

When do photoreceptors hyperpolarize

A

When exposed to light

Goes from -50mV to -70mV

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25
Q

Graded potential in photoreceptors

A

Not all or nothing like some neurons

Greater intensity stimulus causes greater hyperpolarization

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26
Q

Dark current in photoreceptors

A

An+ ions flow through ion Chanel’s into rod outer segment, produces the slight -50mV depolarization

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27
Q

What produces the slight depolarization we see in photoreceptors

A

Dark current

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28
Q

Phototransduction cascade

A

11-cis retinal—

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29
Q

Where does isomerizAtion take place on the 11=cis retinal

A

Between carbons 11 and 12

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30
Q

Comparison of 11-cis to all-trans retinal

A

All-trans: the carbons at 11 and 12 are opposite each other

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31
Q

Visually inert chain of amino acid

A

Opsin

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32
Q

Interlaced into the disc membranes of rod outer segment, determines the absorption profile of the photo pigment

A

Opsin

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33
Q

Repsoisnice to light, consist of retinal, an altered form fo a retinol (vitamin A)

A

Chromophere

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34
Q

I bleached retinal

A

11-cis state

-there is a bend at carbon 11

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35
Q

Absorption fo quantum of light and retinal

A 
Retinal isomerizAtion to all-trans
Transducin activates PDE
PDE breaks down cGMP to CMP
Lower cGMP levels lead to closing of rod outer segment Na+ channels
Results in rod hyperpolarization
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36
Q

ROS sodium channel quantities is limited

A

Constrains the potential magnitude of rod hyperpolarization
When even a small amount of a rods rhodopsin is bleached (all sodium channels are closed, further bleaching does not result in further hyperpolarization), explains psychophysical phenomenon of rod saturation seen in the scotopic light adaption function

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37
Q

Receptor terminals: if it touches just the edges

A

Flat synapse

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38
Q

Widely dispersed dendritic tree synapses with many photoreceptors with substantial summation

A

Horizontal cells

39
Q

H1 cells

A

Input from M and L cones

40
Q

H2 cells

A

Input from S cones

41
Q

Horizontal cells: graded or action potential?

A

Graded potential

42
Q

Bipolar cells: graded or action potential

A

Graded

43
Q

What type of cell displays spatial antagonism

A

Bipolar cells

44
Q

Off-center bipolar cells

A
  • flat synapse
  • outer sub layer (IPL)
  • glutamate is excitatory
45
Q

On-center bipolar cells

A
  • invaginating synapse
  • inter sublayer (IPL)
  • glutamate is inhibitory
46
Q

Amacrine cells

A

Center-surround on some
Action potentials
Brief transient response at stimulus onset and offset

47
Q

Amacrine cell: action or graded potential

A

Action.

48
Q

Brief transient response at stimulus onset and offset

A

Amacrine cells

49
Q

Do amacrine code movement?

A

Possibly, not 100% sure

50
Q

Midget bipolar cells

A

Smaller some
Smaller dendritic tree
Smaller receptive field

51
Q

Diffuse bipolar cells

A
  • center formed by 5-10 m and L cones

- center spectral Sensitivity is similar to the surround

52
Q

Where do you find bipolar midget cells

A

Fovea

53
Q

Another name of the midget GCs

A

Retinal parvo cells

54
Q

Diffuse bipolar cells synapse with

A

Parasol ganglion cells, sometimes referred to as retinal magno cells

55
Q

Parasol GCs constitute _____ of GCs in central 20 degrees and up to ______ more peripherally

A

10%

15%

56
Q

Parvo

A

Sharp vision, 1:1

57
Q

Magno

A

More in the periphery, detects movement

58
Q

Parasol GC

A

Large dendritic trees
Large surround
Center formed by several cones

59
Q

Small bistratisfied GS

A

Receive input from S-cones
8% of ganglion cells
On center formed exclusives by S cones

60
Q

Where do the ganglion cell projections reach

A

LGN (retinogeniculate)

  • parvo-midget GCs
  • magno-parasol GCs
  • Konio-bistratified GCs
61
Q

Eye movements have projections to

A

Superior colliculus

62
Q

Pulmonary

A

Visual attention
Motion processing
Visually guided movement

63
Q

Pretectum

A

Pupil reflex

64
Q

The ganglion cells project to where?

A 
LGN (primarY)
Superior colliculus 
Pulvinar 
Pretectum 
Several small hypothalamic nuclei 
Accessory optic system
65
Q

ARMD

A
  • high density of cones in fovea creates vulnerability
  • fovea damage is devastating
  • ARMD damages choriocapillaris and Bruchs membrane in fovea region (leads to loss of overlying sensory tissue)
  • a leading cause of blindness (especially among retirement aged individuals)
  • angiogenesis blocking drugs may help in wet ARMD
66
Q

This has been limited because have been designed to stimulate GCs with a photoreceptor signal

A

Retinal prosthesis

67
Q

What is your peripheral VA

A

20/200

68
Q

Retinal prosthesis

A

If you could replicate the signal that can go to the GC, you could get much better VA

69
Q

Melanopsin containing ganglion cells

A
  • intrinsically photosensitive retinal ganglion cells
  • project to suprachiasmic nucleus
  • SCN responsible for circadian rhythm
  • show peak sensitivity at 483nm and project to LGN
  • some suggest that stimulation of these cells suppresses release of melatonin (sleep promoting hormone produced by pineal gland)
70
Q

Depression though to be causes by reduction in daylight hours during winter months

A

Seasonal affective disorders

  • for some, mood may be depressed to where it interferes with normal daily activities
  • bright light therapy
71
Q

Bright light therapy for SAD

A
  • patient exposed to a standardized broad spectrum light typically in the morning
  • effectiveness may be due to light altering body’s circadian rhythm
  • melanopsin-containing retinal ganglion cells may play a role
72
Q

Self-luminous electronic displays

A
  • emit bluish light (short wavelengths)
  • may stimulate melanopsin-containing retinal GC
  • suppresses production of melatonin
  • may interfere with sleep patterns in some individuals

CFL and LED light bulbs may have similar effects

73
Q

Retinal ganglion cells project to

A

LGN
Pulvinar
Superior colliculus

74
Q

Retinal ganglion cells project to the

A

LGN

75
Q

AP are produced by

A

Amacrine

Ganglion cells

76
Q

Which of the following would elicit the largest excitatory response in an off-center ganglion cell?

A

Spot of darkness covering only the cells receptive fields center

77
Q

Melanopsin has been found in

A

Ganglion cells

78
Q

The visually inert portion of rhodopsin is the

A

Opsin

79
Q

Immediately prior to exposure to a light, the resting potential of a rod is closest to

A

-50mV

80
Q

With regard to a conventional flat synapse made by a bipolar cell, which of the following is true?

A

The NT is glutamate

It is in the inner plexiform layer

81
Q

Extracellular recording techniques may be used to record the activity of which cells

A

Ganglion

82
Q

A quantum of light is absorbed by rhodopsin. The event immediately preceding the closing of Na pores int he rod outer segment is

A

CGMP to GMP

83
Q

With regard to horizontal cells, which is false?

A

Show spatial antagonism

84
Q

Which is not a characteristic of on-center bipolar cells

A

Glutamate causes depolarization

85
Q

Which of the following would elicit the smalles excitatoy response in an on center parasol ganglion cell

A

Spot of light covering the cells entire receptrove field

86
Q

With regard to the invaginating synapse formed by photoreceptors, horizontal cells, and bipolar cells, which is false?

A

It is located in the outer plexiform layer

It is off center

87
Q

The receptive field center of a fovea midget bipolar cell is formed by how many photoreceptors?

A

One

88
Q

Which bipolar cells manifest color opponency?

A

Midget

89
Q

The first neural cells in the visual pathway to produce graded potentials are

A

Receptor cells

90
Q

The first cells to show clear opponent type response to different portions of the spectrum are

A

Bipolar cells

91
Q

A small spot of light is placed in the receptive field of an on center off surround spatially antagonistic ganglion cell. If the spot is placed directly in the center of the receptive field and then increased in seize from smaller than the on center until larger than the offsurround; the frequency of AP will

A

Increase then decrease

92
Q

When a quantum of light is absorbed by rhodopsin

A

11-cis retinal changes to all-trans retinal

93
Q

The psychophysical phenomenon of rod saturation seen in the scotopic light adaptation function can be best explained by

A

The limited availability of rod outer segment sodium channels

94
Q

On center bipolar cells can be ID by

A

Invaginating synapse

Perception block 11 (8 decks)

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