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PHGY 209 > CNS/sensory 4 - visual > Flashcards

CNS/sensory 4 - visual Flashcards

1
Q

visual perception is dependent on…

A

context
bottom up modification

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1
Q

what is vitreous humour

A

clear jelly

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2
Q

what is retina

A

where transduction occurs

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3
Q

what is retinal pigment epithelium

A

layer of tissue
biochemistry of photoreceptors

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4
Q

what is optic nerve

A

axons of neurons in retina
sending visual info to brai

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5
Q

what is lens

A

can change shape

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6
Q

what is iris

A

changes size of pupil by constricting or dilating

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7
Q

what is pupil

A

behind cornea
can change size
Depends on light levels

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8
Q

what is cornea

A

part of eye
outer clear layer

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9
Q

what is sclera

A

white
becomes transparent in front = cornea

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10
Q

describe blood vessels of eye

A

part blocks photons

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11
Q

what is fovea centralis

A

highest visual acuity
like reading

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12
Q

what is optic disk

A

medial to fovea
blind spot - no photoreceptors here
brain fills it in

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13
Q

what does lens do

A

refracts
bends light to single point

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14
Q

describe how lens refracts light

A

happens when light travels to 2 diff substances
depends on angle of incidence of light and properties of substances
eye collects photons and refracts them - bend in a way where they occur at a single point on retina = focusing

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15
Q

what is light refracted by

A

cornea and lens

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16
Q

which refracts more light - cornea or lens

A

cornea refracts more light
image on retina is inverted
lens = flexible and controlled by some muscles that control its shape

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17
Q

describe accommodation for near vision

A

limited focal range - like if looking at something in distance = lens assumes a shape to focus on retina
if out of focus = ciliary muscles control lens shape
lens accommodates for changes in object location by changing shape

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18
Q

describe nearsightedness

A

eyeball too long
eye is myopic
image created in front of retina
can see objects up close fine but distance = hard
solution = squish eyeball or use corrective lens to compensate for too much refraction and focuses image on retina

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19
Q

describe farsightedness

A

eyeball too short
eye is hyperopic
pull eyeball longer or use lens

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20
Q

describe astigmatism

A

the lens or cornea are not spherical and smooth

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21
Q

describe presbyopia

A

lens gets stiff and is unable to accomodate for near vision
forms of farsightedness that happen after 45 = reading glasses

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22
Q

describe cataract

A

change in lens colour = becomes opaque and blocks photons entering eye

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23
Q

describe basic parts of organization of the retina

A

retinal pigment epithelium (cells interact with photoreceptors)–> transduction (rods and cones) –> change in neurotransmitter release–> processing and convergence (bipolar cells, horizontal cells, amacrine cells)–> becomes optic nerve (vitreous humour and ganglion cells)

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24
describe fovea centralis (organization of the retina)
retinal circuitry is shifted out of the way
25
describe rods and cones (organization of the retina)
2 types of photoreceptors (~100mil/each eye) 1 type of rods = tend to be everywhere else, mediate low light vision, ~5mil in each retina cones = 3 types of cones, mediate colour vision, mostly in fovea, central vision, highest acuity, small rf, ~90 mil in each retina transduction occurs in photoreceptors
26
describe bipolar cells, horizontal cells, amacrine cells (organization of the retina)
circuitry does processes and extracts certain features from visual input converges - optic nerve carries only 1 million
27
describe ganglion cells (organization of the retina) - gen
many photoreceptors drive a few ganglion cells rf= bigger -driven by many rods and less cones fire aps axons = optice nerve
28
describe ganglion cells (organization of the retina) - details
in center of vision - highest acuity = ganglion cells driven by 1,2,3 or 4 cones, in fovea = small rf in periphery = ganglion cells driven by hundred of rods, big rf
29
describe light (organization of the retina)
light entering causes closing of ion channels and photoreceptors changes neurotransmitter release from photoreceptors circuitry of horizontal, bipolar and amacrine cells
30
is retina part of cns
yes technically but also sends info to cns
31
name 2 portions of photoreceptor and describe
outer segment = stacked full of membrane disks = lipid membrane stacked, inner segment = has nucleus - where neurotransmitter released
32
describe phototransduction while in dark
outer segment = lots of cyclic GMP in intracellular space of photoreceptor and lining outer segment = cyclic gmp gated sodium channels (if channels open and photoreceptor depolarizes = neurotransmitter released into circuitry in dark when no photons) photoreceptors releasing neurotransmitters all the time
33
name 4 main steps of photo being released - transduction
light activates opsin molecule g protein cascade cGMP-->GMP channels close
34
describe chromophore (phototransduction)
retinene - inside disk, related to vit a molecule that sits in protein called opsin (captures photons)
35
describe specifically what happens during phototransduction
many disks stacked since photons hard to capture since photon has billions of opsin proteins rhodopsin - for rods photons captured by opsin protein that contains chromophore photon hits opsin molecule and chromophore and opsin separate and causes conformational change in opsin molecule = triggers g protein cascade g protein cascade = motor, so triggers motor to start - can run for a while and converts cgmp to gmp ion channels close - na channels close since less/no cgmp
36
light causes receptors to...
Hyper polarize transmitter released in dark usually, so photons cause reduction in neurotransmitter response
37
how many different opsin molecules are there
4 diff opsin molecules rhodopsin found in rods (3 diff ones for 3 diff types of cones, sensitive to 3 different colours of light)
38
what does middle circuitry do (phototransduction)
doing an inversion - causes reducrion in neurotransmitter to produce an increase drive of ganglion cells fire ap
39
describe rods
high sensivity, night vision more rhodopsin, captures more light high amplification, single photon closes many na+ channels slow response time - lasts longer and slower more sensitivity to scattered light (animals = glowy eyes sine v reflective retinas, light reflected off retina so rods can capture scattered light)
40
describe cones
low sensitivity, day vision less opsin lower amplification since many photons faster response time more sensitive to direct axial rays
41
describe rod system
low acuity - not present in central fovea, highly convergent (many rods drive ganglion cels and rods) achromatic = one type opsin
42
describe cone system
high acuity = concentrated in fovea, less convergent, few cones drive ganglion cells chromatic = three types of opsin
43
describe dark adaptation
bright (rods are inactivated (opsin wiped out since hit with photons), cones are active) --> dark (temporary blindness until rods re-activate and take over, rods have to reconnect with chromophore, involves retinal pigment epithelium, 10-15 mins)
44
describe light adaptation
dark (cones inactive, rods active) --> bright light (rods initially saturated, temporary blindness untill rods inactivate (opsin and chromophores will separate and cannot function) and cones take over)
45
explain light and dark adaptation in more detail
once chromophore and opsin broken = cannot capture photons anymore rods mediate light and dark adaptation takes time to put the chromophore and opsin back together, slow process 10-15 mins
46
what does retina report
relative intensity of light depends on what around it does not tell you exactly how many photons are there, just how many is there compared to surroundings computation done by circuits
47
what do ganglion cells of retina do
not same uniform thing does computation compares middle of receptive field to center
48
what do retinal ganglion cells have
center surround receptive fields
49
name 2 types of ganglion cells
inhibitory surround and excitatory center excitatory surround and inhibitory center
50
what do retinal ganglion cells signal
relative differences of the light - contrast across receptive fields
51
describe inhibitory surround and excitatory center ganglion cell response to lights
bright center dark surround = many aps in center dark center bright surround = no aps in center uniform light = same aps
52
describe inhibitory center and excitatory surround ganglion cell response to lights
bright center dark surround = no aps in center dark center bright surround = many aps in center uniform light = same aps
53
what are photoreceptors sensitive to
wavelength blue, green, red opsin molecule determine chromatic sensitivity of the photoreceptor ganglion cells send info about dark and light and also sends info about colour, depends on which photoreceptors are converging
54
what is perception of colour dependent on
context dependent
55
what do retinal ganglion cells have - for colour
colour opponent receptive fields
56
describe colour opponent receptive fields
green vs red and yellow vs purple output of retina encodes values of brightness and colour colour in middle vs surround
57
describe colour blindness
more than 5% of population has deficit in colour perception some opsins not functioning properly could be due to genetics = perception of colour is different mostly in males could also be caused by damage or diseases and stuff
58
describe flow of visual info in brain
left visual field right visual field temporal retina and nasal retina - temporal retina does not cross axons coming from retinal ganglion cells that are receiving inputs = do cross midline at optic chiasm optic nerve = one eye with both visual fields cross at optic chiasm optic tract = both eyes with contralateral visual field --> lateral geniculate nucleus (thalamus) synapses --> optic radiations towards back of brain --> visual cortext in occipital lobe - both eyes with contralateral visual field
59
lesion in left optic nerve
loss of vision in ipsilateral eye
60
lesion in optic chiasm
bilateral loss of temporal visual fields
61
lesion in left optic tract
loss of contralateral visual field
62
lesion in left occipital lobe
loss of vision in contralateral visual field
63
what does polymodal mean
visual and other sensory modalities combined
64
describe parietal stream
where spatial features and motion large rfs
65
describe primary visual cortex
small rfs simple image features like oriented line segments start to extract basic features which can be put together to make visual image in occipital lobe
66
describe temporal visual stream
what large rfs complex image features selective to high level features hands, places, buildings jennifer aniston neuron
67
describe object recognition
faces
68
where does all parts of visual world come together
in frontal love

PHGY 209 (19 decks)

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