Vision

Question 1

what muscles control pupil diameter

Answer 1

dilator pupillae

sphincter pupillae

Question 2

strength of cornea and lens in diopters?

Answer 2

cornea: 42
len: 20

Question 3

describe emmetropia

Answer 3

when looking at far objects, lens flattens

when looking at near objects, lens bulges

Question 4

descrime myopia (short sightedness)

Answer 4

lens too strong, eye too long. lens accommodates by staying flattened.
near vision is fine.
far vision - focsues before retina.
corrected by concave lens

Question 5

describe hypertropia (far sightedness)

Answer 5

lens too weak, eye too short. lens stays round.
fine for far objects
for near objects, focuses too late
counteracted with convex lens

Question 6

describe snellen chart

Answer 6

distance viewed/distance a normally sighted person can see the thing at

Question 7

describe grating acuity test

Answer 7

easy

Question 8

describe vernier acuity test

Answer 8

easy

Question 9

describe presbyopia

Answer 9

far sightedness that comes from loss of elasticity of lens, so it stays round (old people)

Question 10

what are the two types of photoreceptors

Answer 10

rods and cones

Question 11

describe rods

Answer 11

• high light sensitivity

- single wavelength range: no colour vision

Question 12

describe cones

Answer 12

• low light sensitivity

- 3 wavelength ranges - blue, green, red

Question 13

describe phototransduction when there is light

Answer 13

causes conf change in rhodopsin
activates g protein
turns cGMP to GMP
closes Na+ channel
hyperpolarisation
less glutamate released from photoreceptor

Question 14

describe phototransduction when there isn’t light

Answer 14

no conf change in rhodopsin
cGMP bound to Na+, so it’s open.
relatively more glutamate is released

Question 15

two factors affecting acuity

Answer 15

cone density

convergence ratio

Question 16

describe central retinal (fovea) in terms of cone density and convergence ratio

Answer 16

high cone density/convergence ratio

Question 17

describe peripheral retina in terms of cone density and convergence ratio

Answer 17

low cone density/convergence ratio

Question 18

after photoreceptors, where does glutamate go

Answer 18

bipolar cells

Question 19

are bipolar cells spiking

Answer 19

NO

Question 20

describe off centre bipolar cells

Answer 20

shining light on centre causes hyperpolarisation - conserves sign of photor’s
ionotropic glutamate gated cation channels

Question 21

descirbe on centre bipolar cells

Answer 21

shining light in centre causes depolarisation

has metabotropic g protein goupled receptors

Question 22

are retinal ganglion cells spiking?

Answer 22

yes

Question 23

do retinal ganglion cells have receptive fields?

Answer 23

yes

Question 24

describe parasol cells in terms of
cell body/dendritic arbour/receptive field size
colour sensitivty
sensitivity to rapidly changing stimuli 
which LGN cells they go to

Answer 24

large
not colour sensitive
yes, sensitive
go to magnocellular LGN cells

Question 25

describe MIDGET cells in terms of
cell body/dendritic arbour/receptive field size
colour sensitivty
sensitivity to rapidly changing stimuli 
which LGN cells they go to

Answer 25

small
colour sensitive - receptive fields have yellow-blue and red-green opponency
NA
go to parvocellular layers

Question 26

where is LGN located

Answer 26

thalamus

Question 27

describe layering

Answer 27

bottom two layers: magnocellular layres

top 4 layers: parvocellular layers

Question 28

what happens if you put an electrode perpendicularly in to the layers

Answer 28

htey have the same receptive fields

Question 29

what is PVC aka

Answer 29

area 17, V1, striate cortex

Question 30

describe PVC simple cells

Answer 30

receptive fields have spatially segregated on/off regions
rotation of bar affects AP rate
monocular

Question 31

describe PVC complex cells

Answer 31

receptor fields have spatially homogenous on/off regions
rotation of bar affects Ap rate, but location of bar in receptive field doesnt
binocular

Question 32

describe PVC retinotropic map

Answer 32

adjacent areas of cortex correspond to adjacent areas of visual field
fovea is overrepresented

Question 33

what are the two main pathways from the PVC to the rest of the brain?

Answer 33

parietal/dorsal/where pathway

temporal/ventral/what pathway

Question 34

describe how pupillary reflex can be used to determine optic nerve/oculomotor nerve damage

Answer 34

optic nerve damage: no constriction response in either eye

oculomotor nerve damage: no constriction in the damaged side

Question 35

describe the vestibulo-ocular reflex

Answer 35

sensory: vestibular system
motor: eye movements
- -> since oppostie motor commands need to be generated, inhibition is required.