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neurology > phototransduction and retinal processing > Flashcards

phototransduction and retinal processing Flashcards

1
Q

excitatory NT in the retina?

A

glutamate

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2
Q

5 classes of neurons in retina?

A

! Photoreceptor cells ! Bipolar cells
! Horizontal cells
! Amacrine cells
! Ganglion cells

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3
Q

are there more rods or cones?

A

20 more rods

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4
Q

do photoreceptors divide?

A

no, but they produce more disks (layers) with photopigment

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5
Q

which are more sensitive rods or cones?

A

rods, have more pigment

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6
Q

which has more convergence rods or cones?

A

rods

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7
Q

which amplify more rods or cones?

A

rods

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8
Q

which mediate night vision rods or cones?

A

rods

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9
Q

which mediate day vision rods or cones?

A

cones

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10
Q

which respond faster rods or cones?

A

cones

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11
Q

which do color rods or cones?

A

cones

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12
Q

which have higher acuity rods or cones?

A

cones

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13
Q

which requires the most light to be activated rods or cones?

A

cones, rods can react to a single photon of light

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14
Q

what ion channels are in the outer layer of photoreceptors?

A

Na and some Ca

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15
Q

what keeps the channels open constitutively?

A

cGMP

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16
Q

why are channels kept open constitutively?

A

maintains slight depolarization, -40mV

17
Q

does light cause an increase or decrease in NT release?

A

decrease

18
Q

is cGMP higher in light or dark?

A

in dark, “dark current”, opens Ca2+ channels constitutively at low levels

19
Q

steps of phototransduction activation

A

rhodopsin —> transducin —> phosphodiesterase —> [cGMP] drops —> hyperpolarization

20
Q

steps of termination

A
  • rhodopsin kinase phosphorylates rhodopsin so it now interacts with arrestin
  • reduced [cGMP] allows the rhodopsin kinase activity
  • opsin separates from retinal and all trans retinal returns to cis
21
Q

what does retinal do?

A
  • binds to opsin to form rhodopsin

- turns from cis to trans in presence of photons

22
Q

what determines the optimal wavelength for a given visual pigment?

A

type of opsin, retinal is always the same

23
Q

match colors with their optimal wavelengths

A

blue 420nm
green 531nm
red 558nm

24
Q

which chromosome encodes rod opsin?

A

3

25
Q

which chromosome encodes blue opsin?

A

7

26
Q

which chromosome encodes green/red opsin?

A

X chromosome

27
Q

what are the output cells of the retina?

A

gangion cells

28
Q

three types of ganglion cells:

A

1) on-center - light in center activates
2) off-center - light in surround activates
3) W type - overall reactive - most sensitive to blue light

29
Q

which have larger receptive fields M or P types?

A

M

30
Q

which sense movement M or P?

A

M

31
Q

which sense color M or P?

A

P

32
Q

which type of ganglion cells project to the hypothalamus?

A

W type

33
Q

what area of the brain is involved in pupillary reflexes?

A

pretectal area of midbrain

34
Q

what’s the difference between a direct and consensual pupillary response?

A

direct is ipsilateral and consensual is contralateral

35
Q

Edinger-Westphal nucleus?

A

receives info from both eyes and projects to ciliary ganglion along CN III to smooth muscle of pupillary sphincter

36
Q

what does the superior colliculus do?

A
  • head and eye movements toward visual stimulus

- coordination of visual, auditory, somatic info

37
Q

what part of the brain receives most retinal projections?

A

lateral geniculate nucleus of thalamus

38
Q

which types of ganglion cells project to the lateral geniculate nucleus of the thalamus?

A

M and P

39
Q

how is the lateral geniculate nucleus of the thalamus layered?

A

4 outer layers from parvocellular (P type) cells

2 inner layers from magnocellular (M type) cells

neurology (4 decks)

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