vision

Question 1

macula

Answer 1

area of 95% of our vision
dark spot on eye images

Question 2

when looking at a photo of the eye - what is the white spot

Answer 2

optical nerve

Question 3

optical factors that affect VA

Answer 3

pupil size, refractive errors, clarity of optics

Question 4

fovea

Answer 4

dense area of cones
centre of macula

Question 5

where are there peak rods?

Answer 5

off-centre of macula

Question 6

blind spot

Answer 6

no rods or cones

Question 7

photopigments in rods & cones

Answer 7

rods: rhodopsin
(1 of 3): cone-opsins -> bind to Vit. A

Question 8

vitamin A

Answer 8

receives signal & changes photopigment (like an antenna)
bound to rhodopsin & opsin
both rods and cones

Question 9

phototransduction

Answer 9

photopigments have vitamin A attached
when light enters, 11-cis retinal becomes all-trans retinal (the kink straightens)
this results in a messenger cascade

Question 10

rods vs cones

Answer 10

rods:
Night / BW vision
1 type
Absent from fovea
100 million
More sensitive

cones:
Day / Colour vision
3 types
Densest at fovea
5 million
Less sensitive

Question 11

effect of light on photoreceptors

Answer 11

hyperpolarised

Question 12

state of photoreceptors at night

Answer 12

depolarised due to continuous influx of sodium ions via cGMP

Question 13

state of photoreceptors during day

Answer 13

cGMP -> GMP closes channel
No influx of sodium therefore hyperpolarised

Question 14

passage of info within retina

Answer 14

photoreceptors -> bipolar cells -> ganglion cells

Question 15

lateral interactions

Answer 15

horizontal cells (modify signal as it comes down, see things like flicker & edges)
amacrine cells

Question 16

bipolar cells

Answer 16

2nd order cells
spatial & colour vision

Question 17

ganglion cells

Answer 17

output cells of the retina
release glutamate via a.p. firing

Question 18

ON ganglion cells

Answer 18

depolarise, send a.p. to brain

Question 19

OFF ganglion cells

Answer 19

hyperpolarise, stops a.p. to brain

Question 20

M ganglion

Answer 20

big (big r.f.)
target lateral
motion detection, flicker, gross features

Question 21

P ganglion

Answer 21

small
visual acuity and colour
more numerous

Question 22

receptive fields
(what do they do and how)

Answer 22

maximise edge detection
via. centre-surround organisation

Question 23

lateral inhibition
(horizontal and amacrine)
what nt’s?

Answer 23

via. horizontal cells
provide output to photoreceptors
inhibitory NT GABA
respond to light by hyperpolarising

via. amacrine cells
glycine and gaba NTs

Question 24

visual pathway

Answer 24

retina - optic nerve - lateral geniculate nucleus - optic radiations - V1

Question 25

optic chiasm

Answer 25

fibres from right and left optic nerves combine

Question 26

crossing of vision

Answer 26

L side of both eyes is processed at right side of brain

Question 27

LGN *lateral geniculate nucleus* where in brain & what layers receive what input?

Answer 27

apart of the thalamus layers 1-2: receive input from M layers 3-6: receive input from P

Question 28

ocular dominance columns

Answer 28

functions of neurons in layer 4C

Question 29

orientation columns

Answer 29

neurons best respond to a certain orientation *organised like a box*

Question 30

M type to what layer

Answer 30

to layer 4Ca

Question 31

P type to what layer

Answer 31

to layer 4CB

Question 32

ventral vs dorsal in vision

Answer 32

dorsal: where in visual field ventral: what are you seeing

Question 33

ventral vs dorsal in vision

Answer 33

dorsal: where in visual field ventral: what are you seeing

Question 34

area MT (processes what? input from where? retinotopic info from where?)

Answer 34

processing object motion input from later 4B Retinotopic info from V2 and V3

Question 35

ventral stream *vision*

Answer 35

V1, V2, V4 shape and colour perception

Question 36

area IT *inferior temporal* *ventral stream*

Answer 36

major output of V4 visual memory and perception perception of faces