Visual System I

Question 1

Describe the andromeda galaxy

Answer 1

Can See with naked eye
Problem that visual system has = look at 3d world, electromagnetic light projected onto retina = have to extract 3d word from 2d picture
So have to make assumptions - usually correct
Shape of galaxy = circle tipped on side

Question 2

what general problems is vision solving

Answer 2

Illposed problem
Radiates more light than snowbal in dark room but still know that snowball brighter then lump of coal
We always assume = light comes from top
These assumptions == hard wired by evolution, use assumptions to interpret world = basis of visual illusions

Question 3

describe optical illusion examples

Answer 3

See white triangle on top of other shapes but no actual white triangle - fills in lines = see triangle
Looks curved but lines actually straight, always looks curved now - doesn’t matter that you know straight = will always see curved, cognitively know it’s straight tho - hardline modules built into visual system = cannot override
Colours are the same but look diff = because assume bottom is lighter, also if in shadow = assume its darker
Visual system makes assumptions and adjustments - based on shade vs light
Visual system fills in blank - most of what you see is in canter of vision, resolution in periphery low, high acuity in middle, brain fills in pattern

Question 4

what is sensation

Answer 4

Abstraction ,not replication of real world
Taking in info about world and constructing visual picture

Question 5

is the visual system a camer a

Answer 5

NOOOO
Visual system is not a camera
Image of world = actively built and constructed in head

Question 6

what is eye like

Answer 6

EYE IS like camera

Question 7

describe lens

Answer 7

Focuses light

Question 8

what focuses light

Answer 8

Lens = also focus, bc changes shape=can focus on things far or closer
Cornea = clear outer surface, most of focusing

Question 9

what is retina

Answer 9

Sheet of cells - back of eye
First stage visual processing
Sensitive to light - absorbs light and transformed to electrical signal to brain

Question 10

what is optic disk

Answer 10

Region of collection of axons

Question 11

what is optic nerve

Answer 11

Ganglion cell bodies - axons collect and form optic nerve
No photoreceptors here = blind spot, visual system fills it in tho - do not know it’s there

Question 12

how does light enter eye

Answer 12

Cornea —> lens —> retina

Question 13

ex = tbi what happens to visual field

Answer 13

Lose part of visual field - not black to them , but just not there

Question 14

describe illustration of Retina

Answer 14

Cells and organization
Very complex
But way simpler than brain
Specific cells —> in specific order and info moves through
Retina = pre processes info then goes to brain

Question 15

What does retina consist of

Answer 15

5 main cell types
Diff subtypes tho

Question 16

describe the cells in retina generally

Answer 16

Neurons
Very specialized
Do not fire aps

Question 17

describe order of cells - as light passses through them

Answer 17

Retinal ganglion cells
Amacrine cells
Bipolar cells
Horizontal cells
Photoreceptors

Question 18

describe photoreceptors = cell type of retina

Answer 18

Input cells of retina
2 types =r ods and cones
Cells sensitive to light, absorb photons of light then light transformed to electrical signals

Question 19

describe horizontal cells = cell type of retina

Answer 19

Connect multiple photoreceptors together

Question 20

describe bipolar cells = cell type of retina

Answer 20

Connect photoreceptors and retinal ganglion cells
Photoreceptors —> bipolar cells —> rgcs —> optic nerve —> brain

Question 21

describe amacrine cells = cell type of retina

Answer 21

Horizontal= connect diff ganglion cells together

Question 22

describe retinal ganglion cells = cell type of retina

Answer 22

Output cells of retina = fires aps
Axons collect to form optic nerve

Question 23

why does retina have this special anatomy

Answer 23

Cells clear in retina= light goes through easily,so fine that photoreceptors at back
Cells behind photoreceptors = non neuronal - supporting, help maintain metabolic stuff as photoreceptors are very picky and die fast
At fovea - all other cells pushed off to side

Question 24

how many layers of retina

Answer 24

10 layers

Question 25

What is neural retina

Answer 25

Layers of retina Photoreceptors at back Retinal pigment epithelium under photoreceptors = non neuronal

Question 26

name layers of retina

Answer 26

Ganglion cell axons Ganglion cell bodies Synapses Bipolar, horizontal,amacrine cells bodies Synapses Photoreceptors

Question 27

describe layer output cells of retina

Answer 27

Ganglion cell axons Ganglion cell bodies

Question 28

describe retina layers = synapses = after ganglion cells

Answer 28

Bipolar and ganglion cells and amacrine cells synapses

Question 29

describe retina layers = bipolar, horizontal and amacrine cell bodies

Answer 29

Between synapses

Question 30

describe retina layers = synapses before photoreceptors

Answer 30

between bipolar and photoreceptors and horizontal cells

Question 31

describe retina layers = photoreceptors

Answer 31

Behind = retinal pigment epithelium = rpe = supporting cells, maintain functionality of photoreceptors Pigment = black, absorbs stray light

Question 32

is info flow through retina linear

Answer 32

NOOOOOOOO Lots of processing Way more photoreceptors than ganglion cells = converge onto ganglion cells

Question 33

what is fovea

Answer 33

High acuity centre of visual field Central part retina

Question 34

what happens at fovea

Answer 34

Ganglion cells and bipolar cells are pushed to side Everything pushed to side= light has direct access to photoreceptors = minimizes any kind of distortion

Question 35

describe circuitry of retina generally

Answer 35

At least 17 distinct subtypes rgcs 10 subtypes bipolar cells More than 30 subtypes amacrine cells

Question 36

describe purpose of diff types of retinal ganglion cells

Answer 36

Each ganglion cell conveys specific aspect visual scene - diff colours, illumination, movements Output cells -only cells firing aps Like sub modalities kinda Each = separate labelled line, conveys one aspect of visual world

Question 37

name types of photoreceptors

Answer 37

Rods Cones

Question 38

what is analogous to cell body in photoreceptors

Answer 38

Soma = nucleus Mitochondria = in inner segment = like cell body kinda equivalent

Question 39

describe characteristics of rods

Answer 39

out in periphery If outside - when very dark = use cones Very sensitive to light Rods saturated by light Single rod can change membrane potential -respond to one single photon of visible light - as sensitive as can physically get low acuity, not good at high resolution vision

Question 40

describe morphology of rods

Answer 40

Outer segment = filled with proteins specialized for absorbing light Discs = membrane bound, and stacked in outer segment Absorbs photons and transforms to electrical signal

Question 41

describe characteristics of cones

Answer 41

Centre visual field See with when outside on sunny day, normal light Lower sensitivity but very good at high precision - high resolution vision

Question 42

describe morphology of cones

Answer 42

Outer segment = filled with proteins specialized for absorbing light Discs = part of external memebrane = why cone like shape Absorbs photons and transforms to electrical signal

Question 43

describe synaptic terminal of photoreceptors

Answer 43

= release neurotransmitter Synapse with bipolar cells

Question 44

where are cones concentrated

Answer 44

In fovea Central = all cones As move away from fovea concentration of cones drops off dramatically

Question 45

Where are rods concentrated

Answer 45

Outside fovea As move away from fovea = concentration rods goes way up

Question 46

describe peripheral parts of retina vs central parts of retina

Answer 46

central = cones = high resolution vision but less sensitive to light, more precise Peripheral parts retina = receives light from periphery = many rods = sensitive to light