vision B

Question 1

how many photoreceptors are in the eye

Answer 1

130 mill

Question 2

what signals do photoreceptors transform light, intensity, colour pattterns into

Answer 2

chemical and electrical signals that trigger activity of retinal cells

Question 3

photoreceptors to ganglion cells

Answer 3

130 to 1

Question 4

what do we use to see the retinal inner surface

Answer 4

clinical opthalmoscope

Question 5

where is the optic disc located

Answer 5

nasaly

Question 6

what is the optic disc

Answer 6

our blind spot

Question 7

where isthe macula/ fovea located

Answer 7

temporally

Question 8

what do rays not have to pass through

Answer 8

retinal pigment epithelium, choriocapilllaris, sclera to reach the epithelium

Question 9

cones

Answer 9

colour specific and high acuity
concentrated in the fovea
end stage diferentiated and non proliferative

Question 10

rods

Answer 10

no colour specificity and low acuity
high sensitivity
in the peripheral retina
end stage diferentiated and non proliferative

Question 11

3 classes of cones

Answer 11

trichromat person has normal colour vision
s cones- short wavelength- blue and purple
m cones- middle wavelength- green
l cones- long wavelength- yellow and red

Question 12

monochromats

Answer 12

totally colour blind with one cone pathway plus rod pathway

Question 13

dichromats

Answer 13

a cone photopigment missing thus only has two cone channels

Question 14

anomalous trichromats

Answer 14

all three cone photopigments with one photopigment anomalous in having a shifted peak sensitivity

Question 15

where are the retinal photoreceptors located

Answer 15

anterior to retinal pigment epithelium and behind all other transparent neural retinal cell layers

Question 16

retinal photoreceptors relationship with RPE - retinal pigment epithelium

Answer 16

have a close physical nad functional relationship

Question 17

what do retinal photoreceptors convert

Answer 17

photonic energy to chemical signals by virtue of thier special cellular structure consisting of an inner cell body and an outer segment of photopigment

Question 18

photoreceptor renewal

Answer 18

stacks of discs of visual pigment molecules pf photoreceptors are constantly renewed with new discs added at the base of the outer segment displacing the old discs up the outer segment and pinched off at the tips and engulfed by retinal pigment epithelium on a diurmal cycle peaking in the morning

Question 19

rhodopsin in the dark

Answer 19

unstimulated, cgmp is available and binds to cation channels and those channels and kep t open by the cgmp wihch depolarizes the photoreceptor

Question 20

rhodopsin in light

Answer 20

stimulated starting a cascade involving transducin and phosphodiesterase PDE becomes more activated which then degrades cgmp. cgmp levels begin to decrease and cation channels begin to close and start to hyperpolarize the photoreceptor

Question 21

what sends impulses to the visual cortex

Answer 21

Bipolar cells and ganglion cells

Question 22

what does photoreceptor hyperpolarization lead to

Answer 22

decreased release of inhibitory neurotransitter such as glutamate onto downstream retinal neurons which leads to increased action potentials in these downstream neurons

Question 23

rod to ganglion cell connections

Answer 23

high convergence- less cell to cell connections

Question 24

cone to ganglion cell connections

Answer 24

low convergence- more cell to cell connections

Question 25

why is rods resolution low

Answer 25

bc of the way the wiring is done and rods have high convergence so lower resolution

Question 26

what do horizontal cells do

Answer 26

connect photoreceptors laterally and dampen cells surrounding the centre of maximal receptive stimulation. inhibit surrounding less stimulated cells and effect lateral inhibition

Question 27

cone cells are

Answer 27

receptive fields for GC

Question 28

ganglion cells serve

Answer 28

cone based receptive fields

Question 29

what are the two types of ganglion cells that cone photoreceptors synapse with

Answer 29

on and off centre ganglion cells

Question 30

on centre, off surround field

Answer 30

excites ganglion cell that response to on centre light
inhibit off centre ganglion cell

Question 31

off centre, on surround field

Answer 31

inhibits ganglion cell that responds to on centre light
exites off centre ganglion cell

Question 32

diffuse light on both centre and surround

Answer 32

weak response from both on and off centre ganlgion cells

Question 33

what kind of inhibition do peripheral cones do

Answer 33

compared to foveal cones their connect to more horizontal cells which further inhibit neighbouring cells getting weaker stimuli which optimizes acuity

Question 34

temporal and nasal axons crossing

Answer 34

temporal stay temporal and nasal cross at optic chiasm

Question 35

retinal pathology

Answer 35

showed by clinical opthalomoscope
retinopathy

Question 36

what is the macula

Answer 36

extension of the fovea

Question 37

optic disc location

Answer 37

nasal and fovea is temporal

Question 38

retinal pigment epithelium purpose

Answer 38

to take up the garbage made by the photoreceptors

Question 39

what do horizontal cells do

Answer 39

allow photoreceptor cells to modulate each other

Question 40

rhodopsin

Answer 40

a type of opsin