The Retina

Question 1

What are the functions of the retina?

Answer 1

translates light into a biological signal (using photoreceptors). these signals are transmitted to the brain for further visual processing via the optic nerve

Question 2

What order are bipolar cells

Answer 2

2nd order neurons

Question 3

what type of potential change to bipolar cells show?

Answer 3

graded change

Question 4

what are the 2 types of Bipolar cells?

Answer 4

ON and OFF

Question 5

where do the dendrites of bipolar cells go?

Answer 5

up to photoreceptors

Question 6

where to the processes of bipolar cells go?

Answer 6

make connections to ganglion cells

Question 7

what do bipolar cells release?

Answer 7

glutamate

Question 8

describe ON bipolar cells

Answer 8

respond to reduction in glutamate by becoming excited (depolarise in response to light) They use GPCR glutamate receptor

Question 9

describe OFF bipolar cells

Answer 9

respond in increase of glutamate by becoming excited and depolarised (in dark)- hyperpolarized in light. Have an ionotropic glutamate receptor.

Question 10

can bipolar cells produce APs?

Answer 10

no- only graded changes in membrane potential

Question 11

Where does signal go after bipolar cells?

Answer 11

retinal ganglion cells

Question 12

what are the 2 types of retinal ganglion cell?

Answer 12

ON and OFF

Question 13

what are ON RGCs attached to?

Answer 13

ON bipolar cells (and vice versa)

Question 14

are RGCs excited or inhibited by glutamate?

Answer 14

Excited (therefore excited in dark)

Question 15

are both ON and OFF signals from RGCs transmitted to brain?

Answer 15

yes

Question 16

where does each RGC receive information from?

Answer 16

a patch of retina- rather than a single cell

Question 17

what is the patch of retina the RGCs receive information from called?

Answer 17

receptive field

Question 18

what’s the purpose of amacrine and horizontal cells?

Answer 18

bring together information from the photoreceptors with the RGCs and bipolar cells

Question 19

What do horizontal cells do?

Answer 19

(clue’s in name) allow horizontal flow of information in retina (so it’s not just up/down)

Question 20

what do amacrine cells do?

Answer 20

connect bipolar and RGCs

Question 21

how do amacrine and horizontal cells affect the RGCs?

Answer 21

allow signalling process to change the RGCs activity in a way more complex than simply how light falls

Question 22

What is meant by horizontal cells being sign-inverting?

Answer 22

hyperpolarisation becomes depolarisation and vice versa.

Question 23

what do horizontal cells connect?

Answer 23

neighbouring photoreceptors

Question 24

what does the sign-inverting do?

Answer 24

dampens down signals

Question 25

what are ON centre RGCs?

Answer 25

retinal ganglion cells which are excited by central light rather than surround intensity

Question 26

what are OFF centre RGCs?

Answer 26

cells which are excited when light light intensity in central field of vision is lower than surround

Question 27

what types of things do retinal ganglion cells detect?

Answer 27

spatial contrast, movement in particular direction, general movement, colour, brightness.