Retina

Question 1

How many neurons in the retinal structure?

Answer 1

6

Question 2

What is the functional pathway?

Answer 2

Photoreceptors
Bipolar cells
Ganglion Cells

Question 3

which two pathways do photoreceptors signal in the retina?

Answer 3

the ON and OFF pathyways due to glutamate receptor on BCs

Question 4

Visual acuity is best for which type of Photoreceptor? why?

Answer 4

cone vision b/c low convergence of pathway

Question 5

what 2 things limit visual acuity?

Answer 5

1. neural foctors

2. optical factors

Question 6

3 big optical factors

Answer 6

1. pupil size
2. clarity of optical media (eg. cataracts)
3. refractive errors/blur (myopia)

Question 7

how far away from fovea to get Visual acuity loss?

Answer 7

5 minutes of arc away

Question 8

what is photopic light level?

Answer 8

bright

Question 9

what is scotopic light levels?

Answer 9

darker

Question 10

where and what do you see best in scotopic light levels?

Answer 10

5-15degrees with your Rods

Question 11

what are the six neurons in the retina?

Answer 11

Rods
cones
Horizontal cells
Bipolar Cells
Amacrine Cells
Ganglon cells

Question 12

Rods vs. Cones re: sensitivity

Answer 12

rods more sensitive

Question 13

Rods vs. Cones re: how many types?

Answer 13

Rods: one type
Cones: 3 types

Question 14

Rods vs. Cones number of cells?

Answer 14

Rods: 100 million
Cones: 5 million

Question 15

what one thing do you need for good visual acuity?

Answer 15

small closely packed detectors

Question 16

why are rods visual acuity not as good as cones?

Answer 16

connectivity

Question 17

light on photoreceptors BCs causes what two things?

Answer 17

OFF: hyperpolarization
ON: depolarization

Question 18

what are the two cells that deal with lateral interactions?

Answer 18

Horizontal cells

amacrine cells

Question 19

Horizontal cells does what? how?

Answer 19

inhibit via GABA causing hyperpolarization

Question 20

what is the ‘through’ pathway?

Answer 20

Ph>BC>GC

Question 21

Amacrine cells does what? how?

Answer 21

Axonless Cells and inhibitory via glycine/GABA

Question 22

Ganglion cells are the only cells that do what?

Answer 22

fire action potential

rest are graded potential

Question 23

Ganglion cells are where? do what? how?

Answer 23

main output of retina
depolarize via glutamate
fire action potentials

Question 24

what is a receptive field property?

Answer 24

GCs have a concentric-surround receptive field. they act as comparators not just a detector

Question 25

Photopigments for rods vs. cones? bind to?

Answer 25

Rods: Rhodopsin Cones: Cone-opsins Both bind to Vitamin A

Question 26

Photoreceptors depolarized by light? which NT?

Answer 26

Nope, hyperpolarized via glutamate

Question 27

Photoreceptors fire action potentials?

Answer 27

Nope. graded changes in membrane potential

Question 28

How do you get graded membrane potential in dark and light?

Answer 28

1. Dark: cGMP gates a Na+ channel: continuous influx = depolarization 2. light: cGMP breaks down: no Na+ influx =hyperpolarization

Question 29

What are the steps in photo transduction?

Answer 29

1. light activates rhodopsin 2. cascade close cGMP Na+ channels 3. Rh>transducin>phosphodiesterase>break cGMP 4. hyperpolarization

Question 30

How do ON and OFF Bipolar Cells interact?

Answer 30

Both are activated simultaneously

Question 31

what is the centre-surround?

Answer 31

centre: through pathway surround: determined via input to horizontal cells and their output to photoreceptors

Question 32

horizontal cells release?

Answer 32

GABA

Question 33

what is the surround in centre-surround?

Answer 33

surround: action of horizontal cells on the central group of photoreceptors, determined by the wiring

Question 34

What is melanoma associated retinopathy? how Rx?

Answer 34

Antibodies against ON bipolar cells | Rx: oral prednisolone