lecture 10 - evelyne sernagor

Question 1

rods converge onto bipolar cells do not access RGCs directly, the connections are via…

Answer 1

A2 amacrine cells

Question 2

what do the A2 amacrine cells release

Answer 2

glycine (inhibitory NT)

Question 3

Rod drive only what type of RGC

Answer 3

ON RGCs

Question 4

Cones diverge onto bipolar cells that directly drives…

Answer 4

RCGs (ON and OFF)

Question 5

Rods and cones are weakly coupled via gap junctions, this plays a role in..

Answer 5

the switch between rod pathway function at night and cone pathway function during the day

Question 6

are most amacrine cell inhibitory or excitatory

Answer 6

inhibitory (GABA, glycine)

Question 7

what do amacrine cells do

Answer 7

they shape the temporal aspect of visual signals by gating (inhibiting) ON and OFF bipolar cells to ganglion cells

Question 8

ganglion cells can be divided into what 3 classes

Answer 8

Midget / parvocellular - P (80-90% of RGCs)
Parasol / magnocellular -M (10-20%)
K cells / koniocellular

Question 9

which cells are basis for the ‘what’ pathway (e.g form and colour)

Answer 9

midget and K cells

Question 10

which cells are basis for the ‘where’ pathway (e.g motion and distance)

Answer 10

Parasol cells

Question 11

in the midget ganglion cells there is colour opponency
(yellow is combined activity of medium (green) and long (red) wavelength cones)

Answer 11

some RGCs respond when yellow is in the centre and blue is in the surround (and vice versa)
and some RGCs respond when red is in the centre and green in the surround (and vice versa)

Question 12

diseases:
what are optic neuropathies

Answer 12

diseases in which the ganglion cells and the optic nerve degenerate
light can still be converted into neural signals but communication with the visual centres of the brain is lost
e.g glaucoma

Question 13

photoreceptor dystrophies

Answer 13

diseases where the photoreceptors degenerate
light cannot be converted into neural signals but the ganglion cells and the optic nerve still works so the retina can still communicate with the brain
e.g age related macular degeneration

Question 14

retinal prosthetics to help with photoreceptor dystrophies

Answer 14

creates light perception in a blind person by direct electrical stimulation of a small area of RGCs with an array of electrodes, bypassing the degenerated photoreceptors

Question 15

optogenetics

Answer 15

make cells express light sensitive ionic channel (rodopsin) e.g ganglion cells

Question 16

what was found to prevent photoreceptor death

Answer 16

saffron