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NYCC Neuro 2 > Phototransduction > Flashcards

Phototransduction Flashcards

1
Q

in the dark, what is the membrane potential of the retina?

A

-40mV (depolarized)

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2
Q

why is the retina depolarized in the dark?

A

sodium channels are kept open

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3
Q

what is the enzyme that produces cyclic guanosine monophosphate (cGMP)?

A

enzyme guanylate cyclase

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4
Q

where is cyclic guanosine monophosphate produced?

A

in the photoreceptor

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5
Q

what is the function of cyclic guanosine monophosphate?

A

keeps Na+ channels open (-40mV)

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6
Q

light travels through the retinal layers and is absorbed by the ____

A

pigment epithelium

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7
Q

when light is absorbed, it triggers…

A

absorption of electromagnetic radiation by the photopigment in membrane of stacked discs in photoreceptor’s outer segment

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8
Q

light causes ____ of the retina (photoreceptors)

A

hyperpolarization

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9
Q

the photopigment in the rods is called ____

A

rhodopsin (retinal bound to an opsin)

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10
Q

retinal is a derivative of ____

A

vitamin A

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11
Q

what is opsin?

A

seven membrane, alpha helices receptor protein
like G protein coupled receptors

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12
Q

how many opsins do cones have?

A

3

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13
Q

Young-Helmholtz trichromacy theory

A

states that the combination of relative excitation & inhibition of the red, blue, & green opsins in the cones accounts for our colour vision

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14
Q

light ____ retinal, which activates ____

A

bleaches (cis to trans)
opsin

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15
Q

activation of opsin stimulates ____ in the ____, which activates ____

A
  • G protein: Transducin in disc membrane
  • effector enzyme: phosphodiesterase (PDE)
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16
Q

PDE breaks down ____, which causes…

A

cGMP
Na+ channels close -> photoreceptor membrane potential hyperpolarizes to -70mV

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17
Q

hyperpolarization of the photoreceptor membrane causes…

A

amount of glutamate released to decrease

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18
Q

what happens to photoreceptor sensitivity to light when we go from a lit room to a dark room?

A

sensitivity to light increased 1,000,000x

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19
Q

when going from light to dark, the pupils ____, causing…

A

dilate
unbleached rhodopsin to regenerate in rods (trans to cis) via a process that requires Ca++

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20
Q

what is receptive field?

A

area of the retina that when stimulated by light, changes the cell’s membrane potential

21
Q

what are the 2 receptive fields?

A

center & surround

22
Q

center receptive field

A

photoreceptors that directly synapse with the bipolar cell

23
Q

surround receptive field

A

surrounding photoreceptors that synapse on horizontal cells, which synapse with the bipolar cell

24
Q

the receptive fields centers are ____istic

A

antagonistic:
- ONcenter/OFFsurround
- OFFcenter/ONsurround

25
Q

when do ON bipolar cells depolarize?

A

in the light (in center receptive field)

26
Q

How are ON bipolar cells are depolarized?

A
  • less glutamate released by photoreceptors
  • G-protein coupled glutamate receptors on bipolar cells cause depolarization of bipolar cells
27
Q

when do OFF bipolar cells depolarize?

A

in the dark

28
Q

How are OFF bipolar cells are depolarized?

A
  • more glutamate released by photoreceptors
  • glutamate-gated direct ion channels cause depolarization of the bipolar cell
29
Q

a) when exposed to light, what happens to photoreceptors in the receptive field center of an ON-center bipolar cell?
b) What does the bipolar cell do?

A

a) hyperpolarize
b) depolarize

30
Q

a) when exposed to light, what happens to photoreceptors in the receptive field surround of an ON-center bipolar cell?
b) What does the bipolar cell do?

A

a) hyperpolarize
b) hyperpolarize

31
Q

a) In the dark, what happens to photoreceptors in the receptive field center of an ON-center bipolar cell?
b) What does the bipolar cell do?

A

a) depolarize
b) hyperpolarize

32
Q

a) In the dark, what happens to photoreceptors in the receptive field surround of an ON-center bipolar cell?
b) What does the bipolar cell do?

A

a) depolarize
b) depolarize

33
Q

a) In the light, what happens to photoreceptors in the receptive field center of an OFF-center bipolar cell?
b) What does the bipolar cell do?

A

a) hyperpolarize
b) hyperpolarize

34
Q

a) In the light, what happens to photoreceptors in the receptive field surround of an OFF-center bipolar cell?
b) What does the bipolar cell do?

A

a) hyperpolarize
b) depolarize

35
Q

a) In the dark, what happens to photoreceptors in the receptive field center of an OFF-center bipolar cell?
b) What does the bipolar cell do?

A

a) depolarize
b) depolarize

36
Q

a) In the dark, what happens to photoreceptors in the receptive field surround of an OFF-center bipolar cell?
b) What does the bipolar cell do?

A

a) depolarize
b) hyperpolarize

37
Q

ganglion cells have ____ receptive fields

A

antagonistic

38
Q

ganglion cells in the retina are mainly responsive to…

A

differences in illumination within their receptive fields

39
Q

name the 2 types of ganglion cells

A

M cells (magnocellular)
P cells (parvocellular)

40
Q

M cells

A
  • large receptive fields
  • respond to object motion & low contrast stimuli
  • aid in low resolution vision
41
Q

P cells

A
  • small receptive fields
  • colour opponent cells (sensitive to wavelength): red-green, blue-yellow
  • responsible for colour vision and discrimination of fine detail
42
Q

layers 1,2 of the lateral geniculate nucleus contain ____ cells and receive synapses from ____

A

M cells
M ganglion cells

43
Q

layers 3,4,5,6 of the lateral geniculate nucleus contain ____ cells and receive synapses from ____

A

P cells
P ganglion cells

44
Q

layers 1,4,6 receive fibers from the ____ retina

A

contralateral

45
Q

layers 2,3,5 receive fibers from the ____ retina

A

ipsilateral

46
Q

LGB fibers from the ipsilateral retina end up in the primary visual cortex next to…

A

LGB fibers from contralateral retina
(alternating ocular dominance columns)

47
Q

what happens to information from M cells that reaches the primary visual cortex?

A

streamed through V2 (areas 18,19) to the parietal cortex for analysis of motion

48
Q

what happens to information from P cells that reaches the primary visual cortex?

A
  • separates info about shape (ends in interblobs) and colour (ends in blobs)
  • 2 channels are streamed through V2 to temporal cortex for shape & colour perception and visual memory

NYCC Neuro 2 (28 decks)

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