vision

Question 1

visual stimulus undergoes ___________ to become action potential in the brain.

sensation is action potential in the _________ while perception is __________ of that action potential by the nervous system.

Answer 1

transduction

brain; interpretation

Question 2

environmental stimuli is

(A) perceived by process of _______________

and

(B) interpreted by process of _______________

Answer 2

sensation; perception

Question 3

retina contains visual ____________ and _________________. it is embedded within the _______________________, which supports and maintain the ________________.

Answer 3

interneurons; photoreceptors; pigmented epithelium; photoreceptors

Question 4

on optic disk

• a source of _____________
• ______________ of the optic nerve
• no photoreceptors; ________________

Answer 4

blood supply
beginning
blindspot

Question 5

which component of the eye is not covered by blood vessels?

Answer 5

macula

responsible for central vision, detailed sight, such as reading and recognizing faces

high concentration of photoreceptor cells, particularly cones, which are sensitive to color and fine detail

Question 6

the fovea is in the _________ of the retina, and contains only ___________ in humans.

Answer 6

macula; cones (sensitive to color and fine detail)

Question 7

retinal comes in 2 forms. what are they?

Answer 7

11-cis and all-trans

Question 8

(a) 11-cis retinal + opsin = ___________, which (b) absorbs _______ and (c) breaks apart into ____________ + opsin.

this process is called_______________.

Answer 8

rhodopsin; light; all-trans retinal

bleaching

Question 9

what are the 3 steps in bleaching?

Answer 9

1. 11-cis retinal + opsin = rhodopsin
2. rhodopsin absorbs light
3. rhodopsin breaks into all-trans retinal + opsin

Question 10

photoreceptor response in the dark:

cGMP produced by _______ keeps _______ channels open

____ ions enter cell

photoreceptors ____________

______________ release of glutamate

Answer 10

photoreceptor; NA+

NA+

depolarise

increased

Question 11

In low light, photoreceptors are __________ and release ___________ neurotransmitters, while in bright light, they ____________ and release ___________ neurotransmitters.

Answer 11

depolarised; more; hyperpolarise; less

Question 12

unlike all-or-none action potentials, photoreceptors produce __________ potential whereby the amount of ____________ release depends on ______ or ____________ of light.

Answer 12

graded; neurotransmitter; intensity; brightness

Question 13

photoreceptor response in the presence of light:

_________ absorbs light and breaks apart into _________ and ________

enzymes are released to break down ______

NA+ channels _____ in the absence of _________

photoreceptor ___________

___________ release of glutamate

Answer 13

rhodopsin; all-trans retinal; opsin

cGMP

close; cGMP

hyperpolarise

decreased

Question 14

what does the horizontal cells in the retina do?

Answer 14

1. integrates signal from photoreceptors
2. outputs graded potentials to bipolar cells

Question 15

each bipolar cell has a _____ field. this field captures light signal from ________ which are directly and indirectly connected to the ______ cell. it also ______ graded potentials.

Answer 15

receptive; photoreceptors; bipolar; outputs

Question 16

photoreceptors are also known as __ and _______. in the retina, it is mainly __________, with an especially high concentration in the __________.

Answer 16

rods; cones; cones; fovea

Question 17

photoreceptors are located near the ________ because:

1. recycle the photopigment aka _________, which disintegrates upon contact with _________
2. photoreceptors need constant ________ from the epithelium
3. photoreceptors receive nutrients from the __________ just behind the epithelium

Answer 17

epithelium

rhodopsin; light

maintenance

choroid

Question 18

__________ cell axons exit each eye through the ________, forming an ________ leaving each eye.

Answer 18

ganglion; optic disk; optic nerve

Question 19

optic nerves partially cross at the ___________.

outer half remains on _________ side of the brain, inner half (near nose) travels __________ to other side of brain.

as optic nerves cross the optic chiasm, they become optic ______.

Answer 19

optic chiasm

ipsilateral (same side); contralaterally (opp sides)

tracts

Question 20

different cuts of the optic nerves/tracts results in different patterns of blindness.

One optic nerve:

Optic chiasm:

One optic tract:

Answer 20

One optic nerve: Blindness in one eye. **if right optic nerve cut, then right eye blind

Optic chiasm: Loss of peripheral vision in both eyes (bitemporal hemianopsia).

One optic tract: Loss of the same visual field in both eyes (homonymous hemianopsia). **If left optic tract is cut, the result is “right homonymous hemianopsia.” This means the individual will lose the right visual field in both the left and right eyes.

Question 21

do all optic nerves end up in the striate cortex?

Answer 21

no.

• lateral geniculate nucleus (LGN) in thalamus (visual perception - critical hub that integrates and relays visual information to cortex)
• superior colliculus (visual processing and the coordination of eye movements)

Question 22

how many layers does lateral geniculate nucleus (LGN) in thalamus have? what are they?

Answer 22

6

2 magnocellular layers

4 parvocellular layers

in between these layers - koniocellular layer (so 5 in total)

Question 23

what do the 2 magnocellular layers in LGN do?

Answer 23

receive input from parasol ganglion cell

contrast and motion processing

Question 24

what do the 4 parvocellular layers in LGN do?

Answer 24

receive input from midget ganglion cells

color processing

detailed vision

Question 25

what do the 5 koniocellular layers in LGN do?

Answer 25

receive input from small bistratified ganglion cells color processing

Question 26

there are 3 kinds of cortical receptive fields. what are they?

Answer 26

1. simple cortical cells - respond to position and orientation of light bars 2. complex cortical cells - respond to orientation and movement (in a specific direction) of light bars 3. end-stopped cells - simple + complex cortical cells - varies response depending of length of light bar within receptive field - boundaries detection

Question 27

bottom up processing vs top down processing

Answer 27

Bottom-Up Processing: - Starts with sensory input, building up from the smallest pieces to form a complete perception - essential for understanding new or complex stimuli Top-Down Processing: - Begins with existing knowledge and expectations, influencing how we perceive sensory information. - crucial for recognizing familiar patterns and making sense of the world efficiently.

Question 28

what is CSF? cats have higher __________ but lower ___________ than humans.

Answer 28

contrast sensitivity function - mapping of contrast thresholds over range of spatial frequencies (how finely divided gratings are) contrast sensitivity; spatial frequency

Question 29

in CSF (constrast sensitivity function, humans have higher __________ but lower ___________ than cats.

Answer 29

spatial frequency; contrast sensitivity

Question 30

2 kinds of cues are responsible for depth perception. what are they?

Answer 30

1. binocular cues - retinal disparity btwn left n right view 2. monocular cues - perspective, texture/shading

Question 31

in binocular cues, ________ cells respond when both eyes are looking at the same object. _________ cells respond to slight differences in images seen by 2 eyes.

Answer 31

binocular; disparity-selective

Question 32

the way we see color, the perception of color, is under what theory?

Answer 32

trichromatic theory - strengths of signals detected by the 3 types of cones (red, green, blue) are interpreted by brain as a visible color

Question 33

why do green and red contrast highly with each other as compared to green and yellow?

Answer 33

pattern of cell responses are more similar between green and yellow than between green and red

Question 34

chromatic adaptation is the event that __________ result from ______________. intense light strikes retina for extended time cones for the color of light become _________ and ______ sensitive to that wavelength of light after staring at red screen for a long time, white screen will be perceived as ___________ because the ________ red light can no longer cancel out green entirely

Answer 34

after images; photopigment bleaching bleached; less green; bleached

Question 35

why do infants prefer high contrast, colorful objects?

Answer 35

they have poor vision

Question 36

what are some age-related vision changes?

Answer 36

1. presbyopia - old sight - slower adaptation to focal distance - hardening of lens 2. slower adaptation to changes in light 3. yellowing of lens - distort perception of green and blue 4. smaller pupils 5. less selectivity in cortical responses to visual stimuli - fewer cells specialise in detecting movement and orientation