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Neuro 2019 Exam 2 > Retina- Vosko > Flashcards

Retina- Vosko Flashcards

1
Q

acuity vs sensitivity

A

more sensitive– less detail

more acuity– more detail

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2
Q

the job of the retina vs. the brain

A

The job of the retina is to break an image down into its component parts.
It’s the job of the brain to reconstruct it

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3
Q

Bipolar cells:

A

Segregation Point

1) “On” or “Off”
2) Connected to Rods or Cones

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4
Q

rod and cone segregation piont

A

color
sensitivity
acuity

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5
Q

retinal ganglion cells

A

Point of convergence where properties are coded by bipolar cells
(“on” bipolar cells synapse with
“on” retinal ganglion cells)

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6
Q

Dark current in receptor cells

A

is tonic.

Light causes hyperpolarization metabotropically

Hyperpolarization achieved by closing Na+ channels

when light hits, glutamate stops.

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7
Q

Rods and cones

A

contain photopigments with responses to light of particular wavelengths

Each photoreceptor cell has sensitivity to light of certain wavelengths, based on photopigment

Color discrimination works by comparing the response of two or more cones to the same light (except with S Cones)

*If there are two or more cone opsins, can perceive colors between the relative contribution of each

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8
Q

Primate retinas are organized specifically to have

A

increased acuity in photopic conditions

Convergence is stronger with rods, makes them more sensitive but less acute

This ratio of cones:bipolar cells is 1:1 in the fovea, where there are no rods, makes them more acute but less sensitive

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9
Q

cones are key for

A

acuity because there is less convergence.

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10
Q

the problem of cones

A

not many of them in relation to the rods.

to overcome it? must amp up the stimulus– need lots of light. This is why we can’t see the details in low light.

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11
Q

rods do what?

A

increase visual sensitivity to low-light conditions using both vertical AND horizontal integration

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12
Q

photopic vs scotopic

A

photopic environment- lots of light
scotopic- dark
mesopic- moonlight

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13
Q

what cells are contacted in what kind of light?

A

Horizontal cells are contacted in scotopic light

Both amacrine and horizontal cells are contacted in mesopic light

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14
Q

ribbon synapses

A

are specialized in neurons that release neurotransmitter tonically AND without Action Potentials (APs)

Orthogonal, planar rows to presynaptic membrane
Graded release of NT
Found in photoreceptors and bipolar cells
Release large amounts of NT
Quickly replenished

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15
Q

ON bipolar cells

A 
¾ of all bipolar cells
hyperpolarize to glutamate
synapse with ON ganglion cells
all rods, some cones
Rod bipolar cells do not directly contact ganglion cells
mGluRs (mGluR6)

ALL ROD BIPOLAR CELLS ARE ON BIPOLAR CELLS

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16
Q

OFF bipolar cells

A

depolarize to glutamate
synapse with OFF ganglion cells
some cones
(AMPA/kainate)

17
Q

How can bipolar cells either hyperpolarize or depolarize to glutamate, an excitatory neurotransmitter?

A

mGluR6 is specifically found postsynaptically on ON bipolar cell dendrites

AMPA/Kainate channels are found on OFF

18
Q

Recording APs from retinal ganglion cells (RGC’s) show

A

that they have a center-surround receptive field

19
Q

Bipolar cells either hyperpolarize or depolarize to light–>

A

RGCs share the same response as the bipolar cell type that innervates them

Horizontal cells are hyperpolarized by light and accentuate contrasts

20
Q

Different types of bipolar cells also encode

A

the duration of a light stimulus

21
Q

amacrine cells

A

further modify the responses of RGCs

30 different types
Release GABA or glycine onto bipolar cells and RGCs
Also contribute to the “surround” response of the center-surround RGC
Co-release other neuropeptides
Necessary to detect motion in the retina

22
Q

wide field amacrine cells

A

subtract background noise from moving objects

23
Q

Starburst amacrine cells

A

respond to signals only in light movement across dendritic fields in a particular direction

24
Q

retinal ganglion cells

A

are the final common pathway of the decomposed image as it will be carried into the brain via the optic nerve

25
Q

melanopsin

A

a circadian photoreceptor?

sits in retinal ganglion cells (these ones respond to light themselves! transmit a non-image signal to other parts of the brain for circadian rhythm entrainment, levels arousal, etc.)

melanopsin, a vitamin-A based opsin photopigment

similar to insect photopigments

from frog melanophores

melanopsin localized to RGC layer of rodents and primates

26
Q

2 functionally distinct light detection systems in mammalian retina

A

image-forming and circadian.

masking
pupillary light reflex
phase shifting

Neuro 2019 Exam 2 (14 decks)

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