Physiology of Vision Flashcards

1
Q

light travels through what structures to get to its desired destination in the retina

A

ganglion cells then
bipolar cells then
photoreceptors

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2
Q

the direction of visual signals travels from what retinal structure to what?

A

photoreceptors to bipolar cells to ganglion cells

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3
Q

which lateral connecting cells of the eye are the closest to the photoreceptors

A

horizontal cells

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4
Q

photoreceptor membranes are usually __polarised at rest

A

depolarised

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5
Q

in the absence of light there is an influx of what? what happens as a result?

A

influx of Na aka the dark current causing photoreceptors to be depolarised at rest

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6
Q

what 2 substances bind to form rhodopsin

A

opsin + 11-cis-retinal

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7
Q

light stimulation of rhodopsin leads to activation of…

A

transducin (a g protein)

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8
Q

the more cGMP, the more ___ ____

A

Na entry

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9
Q

which photoreceptors are for dim light?

A

rods

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10
Q

___ are excluded from the fovea and exist more peripherally

A

rods

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11
Q

the higher the convergence the ___ visual acuity

A

less (large spacing over a large area, less will make it more focused)

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12
Q

what chemical is at a low level in photoreceptors in light?

A

glutamate

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13
Q

what cells are affected when glutamate is low? what happens to them?

A

bipolar cells (become more negative as there is no depolarisation from glutamate)

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14
Q

what receptors respond positively to glutamate?

A

ionotropic glutamate receptors

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15
Q

what receptors respond negatively to glutamate?

A

metabotropic glutamate receptors

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16
Q

what happens to bipolar cells when glutamate is low in metabotropic glutamate receptors

A

become more negative (less glutamate and these receptors respond positively to this so will hyperpolarise)

17
Q

there is more glutamate in the dark T or F

A

T

18
Q

what is the main aim of lateral inhibition?

A

allows sensory neurons to LOCALISE the stimulus

19
Q

horizontal cells are located between

A

photoreceptors and bipolar cells

20
Q

what cells are in charge of centre-surround organisation (a form of lateral inhibition) in the retina?

A

horizontal cells

21
Q

when will an off centre ganglion cell have the highest AP?

A

when the centre of the visual field is dark and the surrounding area is light

22
Q

the fovea takes up a small part of the visual cortex T or F

A

F takes up a very large section (up to half)

23
Q

first monocular layer of the striate cortex?

A

layer 4c

24
Q

first cortical visual area that receives input from the lateral geniculate nucleus?

A

striate cortex

25
Q

LGN location?

A

thalamus

26
Q

retinal synapses in the LGN are not affected by deprivation, why?

A

they are monocular not binocular

27
Q

lesion of the retina causes a…

A

monocular scotoma

28
Q

retrochiasmal lesions cause ____ visual fields

A

homonymous

same visual fields eg nasal and temporal

29
Q

“macular sparing” makes you think the lesion is in the..

A

occipital lobe