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Med School Yr 2 > 3 - The Eye & Retina > Flashcards

3 - The Eye & Retina Flashcards

1
Q

list the layers of the retina beginning with the photoreceptor layer

A
  • photoreceptor layer
  • outer plexiform lyer
  • inner nuclear layer
  • inner plexiform layer
  • ganglion cell layer
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2
Q

which layer of the retina sends signals to the brain?

A

ganglion cell layer

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3
Q

the retinal vasculature of the eye supplies what?

A

the inner retina

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4
Q

the choroidal vasculature of the eye supplies what?

A

the photoreceptors

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5
Q

which vasculature of the eye is disrupted in glaucoma?

A

retinal

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6
Q

which vasculature of the eye is disrupted by retinal detachment?

A

choroidal

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7
Q

what is the role of photoreceptors?

A

transmit light into a biological signal

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8
Q

what is the role of the inner nuclear layer/

A

extract visual information

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9
Q

what is the role of the retinal ganglion cells?

A

transmits signal to the brain

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10
Q

what does the outer segment of the photoreceptor contain?

A

plasma membrane

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11
Q

what does the inner segment of the photoreceptor contain?

A

cilium
mitochondria
golgi

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12
Q

what photopigment do photoreceptors contain?

A

rhodopsin

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13
Q

what does rhodopsin contain?

A

retinaldehyde bound to opsin

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14
Q

11-cis retinal is found in rhodopsin. what structural isoform is it converted into when light is absorbed?

A

all-trans retinal

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15
Q

what is the opsin protein?

A

7 transmembrane domain G protein coupled receptor

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16
Q

what is the function of opsin?

A
  • amplifies isomerisation of retinal into a biological signal
  • determines which wavelengths retinal absorbs
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17
Q

how does 11-cis retinal react with opsin?

A
  • acts as an inverse agonist
  • keeps opsin inactive
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18
Q

how does all-trans retinal react with opsin?

A
  • acts as an agonist
  • initiates signalling cascade
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19
Q

outline the phototransduction cascade in 4 steps

A
  • photon absorption - activates rhodopsin
  • G-protein dissociation - separation of alpha, gamma, beta subunits
  • alpha subunit activates cGMP into phosphodiesterase
  • closure of cGMP-gated channels
20
Q

what happens to the polarity of a photoreceptor in the dark? how does this effect neurotransmitter release?

A
  • depolarises
  • releases lots of glutamate
21
Q

what happens to the polarity of a photoreceptor in the light? how does this effect neurotransmitter release?

A
  • responds to light exposure with graded hyperpolarisation
  • reduces glutamate releases
22
Q

why are rods used at night instead of cones?

A
  • capture more photons
  • have a larger signal amplification
  • so are more sensitive
23
Q

which has a higher acuity - rods or cones?

A

cones

24
Q

which photoreceptor provides colour vision?

A

cones

25
Q

what photoreceptors does the fovea contain?

A

cones

26
Q

the peak absorption for retinal is normally ultraviolet, which humans can’t see. what adaption changes this?

A
  • retinal binds with opsin
  • changes relative sensitivity to wavelengths on a visible spectrum
27
Q

how many cone opsin genes are there?

A

3

28
Q

what creates colour vision?

A
  • 3 cone opsin genes
  • long wave cone - red wavelengths
  • middle wave cone - green wavelengths
  • short wave cone - blue wave lengths
29
Q

what wavelength is associated with long-wave cones?

A

564nm - red

30
Q

what wavelength is associated with middle-wave cones?

A

533nm - green

31
Q

what wavelength is associated with short-wave cones?

A

433nm - blue

32
Q

photoreceptors translate the light intensity pattern into what?

A

a spatial pattern of glutamate release

33
Q

if its dark, is more or less glutamate released?

A

more

34
Q

what connects photoreceptors to retinal ganglion cells?

A

bipolar cells

35
Q

what are the 2 types of bipolar cell?

A
  • sign inverting - “on”
  • sign conserving - “off”
36
Q

what glutamate receptors do sign inverting bipolar cells have? what does this result in?

A
  • metabotropic
  • glutamate activates signalling cascase
  • closes cation channels
37
Q

what glutamate receptors do sign conserving bipolar cells have? what does this result in?

A
  • ionotropic
  • cation channels are opened by glutamate
38
Q

are sign inverting bi polar cells depolarised or hyperpolarised by a flash of light?

A

depolarised - on

39
Q

are sign conserving bi polar cells depolarised or hyperpolarised by a flash of light?

A

hyperpolarised - off

40
Q

what is the role of horizontal cells?

A

connect neighbouring photoreceptors to amplify local differences in light intensity

41
Q

what happens to horizontal cells if there is a light spot?

A
  • neighbouring cones are depolarised
  • horizontal cells are depolarised
  • signal from the centre cone to bipolar cell enhances
42
Q

what happens to horizontal cells in diffuse light?

A
  • neighbouring cones are hyperpolarised
  • causes horizontal cells to be hyperpolarised
  • signal from centre cone to bipolar cells in dampened
43
Q

as well as enhancing light differences, what other role do horizontal cells have?

A

encode colour

44
Q

what happens to horizontal cells in red light?

A
  • neighbouring cones become more hyperpolarised
  • horizontal cells are moe hyperpolarised
  • signal from centre cone to bipolar cells is reduced
45
Q

what happens to horizontal cells in green light?

A
  • neighbouring cones are less hyperpolarised
  • horizontal cells are less hyperpolarised
  • signal from centre cone to bipolar cells is enhanced
46
Q

what is the role of amacrine cells?

A

provide an inhibitory link between bipolar cells and retinal ganglion cells

47
Q
A

Med School Yr 2 (96 decks)

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