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Perception block 11 > Fucntional Retina > Flashcards

Fucntional Retina Flashcards

(94 cards)

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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
Graded potential in photoreceptors
Not all or nothing like some neurons | Greater intensity stimulus causes greater hyperpolarization
26
Dark current in photoreceptors
An+ ions flow through ion Chanel’s into rod outer segment, produces the slight -50mV depolarization
27
What produces the slight depolarization we see in photoreceptors
Dark current
28
Phototransduction cascade
11-cis retinal—
29
Where does isomerizAtion take place on the 11=cis retinal
Between carbons 11 and 12
30
Comparison of 11-cis to all-trans retinal
All-trans: the carbons at 11 and 12 are opposite each other
31
Visually inert chain of amino acid
Opsin
32
Interlaced into the disc membranes of rod outer segment, determines the absorption profile of the photo pigment
Opsin
33
Repsoisnice to light, consist of retinal, an altered form fo a retinol (vitamin A)
Chromophere
34
I bleached retinal
11-cis state | -there is a bend at carbon 11
35
Absorption fo quantum of light and retinal
``` 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 ```
36
ROS sodium channel quantities is limited
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
37
Receptor terminals: if it touches just the edges
Flat synapse
38
Widely dispersed dendritic tree synapses with many photoreceptors with substantial summation
Horizontal cells
39
H1 cells
Input from M and L cones
40
H2 cells
Input from S cones
41
Horizontal cells: graded or action potential?
Graded potential
42
Bipolar cells: graded or action potential
Graded
43
What type of cell displays spatial antagonism
Bipolar cells
44
Off-center bipolar cells
- flat synapse - outer sub layer (IPL) - glutamate is excitatory
45
On-center bipolar cells
- invaginating synapse - inter sublayer (IPL) - glutamate is inhibitory
46
Amacrine cells
Center-surround on some Action potentials Brief transient response at stimulus onset and offset
47
Amacrine cell: action or graded potential
Action.
48
Brief transient response at stimulus onset and offset
Amacrine cells
49
Do amacrine code movement?
Possibly, not 100% sure
50
Midget bipolar cells
Smaller some Smaller dendritic tree Smaller receptive field
51
Diffuse bipolar cells
- center formed by 5-10 m and L cones | - center spectral Sensitivity is similar to the surround
52
Where do you find bipolar midget cells
Fovea
53
Another name of the midget GCs
Retinal parvo cells
54
Diffuse bipolar cells synapse with
Parasol ganglion cells, sometimes referred to as retinal magno cells
55
Parasol GCs constitute _____ of GCs in central 20 degrees and up to ______ more peripherally
10% | 15%
56
Parvo
Sharp vision, 1:1
57
Magno
More in the periphery, detects movement
58
Parasol GC
Large dendritic trees Large surround Center formed by several cones
59
Small bistratisfied GS
Receive input from S-cones 8% of ganglion cells On center formed exclusives by S cones
60
Where do the ganglion cell projections reach
LGN (retinogeniculate) - parvo-midget GCs - magno-parasol GCs - Konio-bistratified GCs
61
Eye movements have projections to
Superior colliculus
62
Pulmonary
Visual attention Motion processing Visually guided movement
63
Pretectum
Pupil reflex
64
The ganglion cells project to where?
``` LGN (primarY) Superior colliculus Pulvinar Pretectum Several small hypothalamic nuclei Accessory optic system ```
65
ARMD
- 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
This has been limited because have been designed to stimulate GCs with a photoreceptor signal
Retinal prosthesis
67
What is your peripheral VA
20/200
68
Retinal prosthesis
If you could replicate the signal that can go to the GC, you could get much better VA
69
Melanopsin containing ganglion cells
- 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
Depression though to be causes by reduction in daylight hours during winter months
Seasonal affective disorders - for some, mood may be depressed to where it interferes with normal daily activities - bright light therapy
71
Bright light therapy for SAD
- 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
Self-luminous electronic displays
- 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
Retinal ganglion cells project to
LGN Pulvinar Superior colliculus
74
Retinal ganglion cells project to the
LGN
75
AP are produced by
Amacrine | Ganglion cells
76
Which of the following would elicit the largest excitatory response in an off-center ganglion cell?
Spot of darkness covering only the cells receptive fields center
77
Melanopsin has been found in
Ganglion cells
78
The visually inert portion of rhodopsin is the
Opsin
79
Immediately prior to exposure to a light, the resting potential of a rod is closest to
-50mV
80
With regard to a conventional flat synapse made by a bipolar cell, which of the following is true?
The NT is glutamate | It is in the inner plexiform layer
81
Extracellular recording techniques may be used to record the activity of which cells
Ganglion
82
A quantum of light is absorbed by rhodopsin. The event immediately preceding the closing of Na pores int he rod outer segment is
CGMP to GMP
83
With regard to horizontal cells, which is false?
Show spatial antagonism
84
Which is not a characteristic of on-center bipolar cells
Glutamate causes depolarization
85
Which of the following would elicit the smalles excitatoy response in an on center parasol ganglion cell
Spot of light covering the cells entire receptrove field
86
With regard to the invaginating synapse formed by photoreceptors, horizontal cells, and bipolar cells, which is false?
It is located in the outer plexiform layer | It is off center
87
The receptive field center of a fovea midget bipolar cell is formed by how many photoreceptors?
One
88
Which bipolar cells manifest color opponency?
Midget
89
The first neural cells in the visual pathway to produce graded potentials are
Receptor cells
90
The first cells to show clear opponent type response to different portions of the spectrum are
Bipolar cells
91
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
Increase then decrease
92
When a quantum of light is absorbed by rhodopsin
11-cis retinal changes to all-trans retinal
93
The psychophysical phenomenon of rod saturation seen in the scotopic light adaptation function can be best explained by
The limited availability of rod outer segment sodium channels
94
On center bipolar cells can be ID by
Invaginating synapse

Perception block 11 (8 decks)

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