Vision I: Retinal Function Flashcards Preview

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Flashcards in Vision I: Retinal Function Deck (28):
1

Major cells of retina

photoreceptors (rods and cones), bipolar cells, ganglion cells, horitzontal and amacrine cells, muller cells, retinal pigment epithelium, blood vessels, collagen

2

Rods/cones are what order neurons?

First order

3

Ratio of rods and cones

Many more rods (100 million) than cones (5 million)

4

Bipolar cells are what order neurons?

seconds order

5

Ganglion cells

3rd order neurons, connect retina to the brain (LGN), unmyelinated axons transverse inner retina become myelinated by optic nerve oligodendrocytes, involved in convergence

6

Horizontal and amacrine cells

interneurons with specific roles in center and dark vision

7

Which cells work as retinal astrocytes (GFAP+)>

Muller cells

8

RPE

important regulator of PR health

9

Branches of what artery run through retina?

central retinal artery

(choroidal vasculature provides supply to PRs)

10

Vasculature to fovea?

NOPE. (foveal avascular zone) since it's involved in processing color

11

Where do we find photoreceptors? (PRs)

in fovea - cones abundant, provide fine detail and color vision
rods - not in fovea, most of them are lateral

12

Compare and contrast structural features of rods and cones

rods - free floating
cones - attached to plasma membrane

rods are longer, steeper
cones - thicker, shorter

both have outer and inner segments, both have cilium

13

How is PR excitability different from other cells?

in the dark, channels open, partially depolarized

AT REST, THE CURRENT FLOW IS ALREADY PARTIALLY DEPOLARIZED "DARK CURRENT"

14

Rhodopsin

involved in activation of phototransduction cascade (coordinates with G-protein transducin, GTP)

vitamin A

15

How does phototransduction signal propogate to second order neuron?

Removal of glutamate

16

What is the waste management dohick in photoreceptors?

RPE! phagocytize the most apical outer segment discs and take to lysosomal system, follow circadian rhythms

17

Other functions of RPE?

important!

1. forms blood PR barrier
2. daily phagocytosis of outer segment discs
3. Vit A metabolism (important in phototransduction, trans to cis)
4. melanin production to allow for high acuity (high density melanosomes around cones, low around rods)
5. neovascular barrier to prevent choroidal vasculature from entering subretinal space

18

How are ganglion cells distributed?

high density in mid fovea! very siimilar in distribution to cones (close to 1:1 ratio of cone to GC at the fovea)

19

How are images perceived by eye?

Images are right- left reversed AND up-down inverted

20

X pathway of RGC

small diameter (midget RGCs)
detect fine detail, sharp edges, color, project ot parvocellular layers of the lateral geniculate nucleus (P cells)

21

Y pathway of RGC

large diameter cells with huge dendritic field, detect motion and general shapes, project to M cells

22

W pathway of RGCs

varied size, large dendritic field, used for detection of LIGHT LEVELS not for acuity, do NOT go to lateral geniculate nuclues

23

Types of cones

L cones - red (long wavelength)
M cones - green (middle wavelength)
S cones - blue (short wavelength)

24

How is color vision mediated?

Genetically (opsins are tightly linked on X chormosome for long and middle wavelength, and on chromosome 7 for short wavelength)

25

Protanopia

Loss of L cone function

26

Deuteranopia

loss of M cone function

27

tritanopia

loss of S cone function

28

Receptive field center and surround?

Receptive field center - provides direct info from PRs to bipolar cells

Receptive field surround - indirect info from PRs to bipolar cells via horizontal cells (lateral inhibition)