Retina Flashcards Preview

Jason's Neuro Block > Retina > Flashcards

Flashcards in Retina Deck (34):
1

How many neurons in the retinal structure?

6

2

What is the functional pathway?

Photoreceptors
Bipolar cells
Ganglion Cells

3

which two pathways do photoreceptors signal in the retina?

the ON and OFF pathyways due to glutamate receptor on BCs

4

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

cone vision b/c low convergence of pathway

5

what 2 things limit visual acuity?

1. neural foctors
2. optical factors

6

3 big optical factors

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

7

how far away from fovea to get Visual acuity loss?

5 minutes of arc away

8

what is photopic light level?

bright

9

what is scotopic light levels?

darker

10

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

5-15degrees with your Rods

11

what are the six neurons in the retina?

Rods
cones
Horizontal cells
Bipolar Cells
Amacrine Cells
Ganglon cells

12

Rods vs. Cones re: sensitivity

rods more sensitive

13

Rods vs. Cones re: how many types?

Rods: one type
Cones: 3 types

14

Rods vs. Cones number of cells?

Rods: 100 million
Cones: 5 million

15

what one thing do you need for good visual acuity?

small closely packed detectors

16

why are rods visual acuity not as good as cones?

connectivity

17

light on photoreceptors BCs causes what two things?

OFF: hyperpolarization
ON: depolarization

18

what are the two cells that deal with lateral interactions?

Horizontal cells
amacrine cells

19

Horizontal cells does what? how?

inhibit via GABA causing hyperpolarization

20

what is the 'through' pathway?

Ph>BC>GC

21

Amacrine cells does what? how?

Axonless Cells and inhibitory via glycine/GABA

22

Ganglion cells are the only cells that do what?

fire action potential
rest are graded potential

23

Ganglion cells are where? do what? how?

main output of retina
depolarize via glutamate
fire action potentials

24

what is a receptive field property?

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

25

Photopigments for rods vs. cones? bind to?

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

26

Photoreceptors depolarized by light? which NT?

Nope, hyperpolarized via glutamate

27

Photoreceptors fire action potentials?

Nope. graded changes in membrane potential

28

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

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

29

What are the steps in photo transduction?

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

30

How do ON and OFF Bipolar Cells interact?

Both are activated simultaneously

31

what is the centre-surround?

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

32

horizontal cells release?

GABA

33

what is the surround in centre-surround?

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

34

What is melanoma associated retinopathy? how Rx?

Antibodies against ON bipolar cells
Rx: oral prednisolone