Lecture 24

Question 1

how is cone photopigment distributed

Answer 1

not equally

Question 2

how many short wave lengths sensitive comes are there

Answer 2

5-10%

Question 3

ration of L:M cones

Answer 3

2:1

Question 4

dark current

Answer 4

1. cGMP binds to Na+ and Ca+ permeable channel keeping them open
2. flow of cations into the outer segment in the dark
3. K+ leaves the cell through “leaky” channels in the inner segment
4. The Na+/K+ pump maintains the concentrations of Na+ and K+ inside and outside the cell

Question 5

in the dark the membrane potential of photoreceptors is

Answer 5

~ -40mV

Question 6

Phototransduction

Answer 6

1. absorption of light by chromophore (photo-activation or bleaching)
2. rhodopsin changes conformation therefore is activated
3. active rhodopsin activates a G-protein
4. G-protein activates PDE enzyme
5. PDE breaks down cGMP to GMP
6. cGMP gated channels close

Question 7

What happens to the membrane potential when cGMP-gated ion channels close?

Answer 7

oPhotoreceptors become more hyper polarized

Question 8

what forms a vertical pathway in the retina

Answer 8

Photoreceptors, bipolar cells, and ganglion cells

Question 9

bipolar cells synapse with ____-

Answer 9

neither cones or rods

Question 10

bipolar cells pass info onto

Answer 10

RGCs

Question 11

RGCs are

Answer 11

• The only neurons whose axons leave the eye
• The only retinal neurons that generate action potentials
• The site at which parallel visual streams emerge

Question 12

Foveal vision allows us to see fine details because

Answer 12

• Retinal neurons (except cones) are shifted to one side to allow light unimpeded access to cones
• Cones are tightly packed into foveal regions
• Cones and bipolar cells are connected to each other in a 1:1 ratio (high spatial mapping)
• Fovea has the highest visual acuity, light has a more direct pathway to the back of the eye

Question 13

as you increase eccentricity you _______ convergence

Answer 13

increase

Question 14

periphery has higher _______

Answer 14

convergence?

Question 15

near fovea has ______ resolution

Answer 15

increased

Question 16

P-ganglion cell recieves input from

Answer 16

midget bipolar cells

Question 17

P-ganglion cell size is

Answer 17

small

Question 18

P-ganglion cell is _____% of all RGCs

Answer 18

~70

Question 19

P-ganglion cell are high in density in the ___

Answer 19

fovea

Question 20

M-ganglion cell receives input from

Answer 20

diffuse bipolar cells

Question 21

M-ganglion cell size is

Answer 21

large

Question 22

M-ganglion cell has ______ dendritic field

Answer 22

large

Question 23

P-ganglion cell has ______ dendritic field

Answer 23

small

Question 24

M-ganglion cell is ___% of all RGCs

Answer 24

~10

Question 25

what is a third type of ganglion cell in RGCs

Answer 25

koniocellular

Question 26

Retina does not just detect light it

Answer 26

detects differences in light in adjacent parts of the retina

Question 27

Receptive field

Answer 27

area of the retina (or visual field) that influences the neuron, either by inhibition or excitation

Question 28

2 concentric zones

Answer 28

Excitatory+inhibitory = centre- surround receptive field