Physiology of Vision

Question 1

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

Answer 1

ganglion cells then
bipolar cells then
photoreceptors

Question 2

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

Answer 2

photoreceptors to bipolar cells to ganglion cells

Question 3

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

Answer 3

horizontal cells

Question 4

photoreceptor membranes are usually __polarised at rest

Answer 4

depolarised

Question 5

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

Answer 5

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

Question 6

what 2 substances bind to form rhodopsin

Answer 6

opsin + 11-cis-retinal

Question 7

light stimulation of rhodopsin leads to activation of…

Answer 7

transducin (a g protein)

Question 8

the more cGMP, the more ___ ____

Answer 8

Na entry

Question 9

which photoreceptors are for dim light?

Answer 9

rods

Question 10

___ are excluded from the fovea and exist more peripherally

Answer 10

rods

Question 11

the higher the convergence the ___ visual acuity

Answer 11

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

Question 12

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

Answer 12

glutamate

Question 13

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

Answer 13

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

Question 14

what receptors respond positively to glutamate?

Answer 14

ionotropic glutamate receptors

Question 15

what receptors respond negatively to glutamate?

Answer 15

metabotropic glutamate receptors

Question 16

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

Answer 16

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

Question 17

there is more glutamate in the dark T or F

Answer 17

T

Question 18

what is the main aim of lateral inhibition?

Answer 18

allows sensory neurons to LOCALISE the stimulus

Question 19

horizontal cells are located between

Answer 19

photoreceptors and bipolar cells

Question 20

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

Answer 20

horizontal cells

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

first monocular layer of the striate cortex?

Answer 23

layer 4c

Question 24

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

Answer 24

striate cortex

Question 25

LGN location?

Answer 25

thalamus

Question 26

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

Answer 26

they are monocular not binocular

Question 27

lesion of the retina causes a…

Answer 27

monocular scotoma

Question 28

retrochiasmal lesions cause ____ visual fields

Answer 28

homonymous

same visual fields eg nasal and temporal

Question 29

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

Answer 29

occipital lobe