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CSB332 > 09 | Sight > Flashcards

09 | Sight Flashcards

1
Q

how many ganglion cells do we have?

A

1.2 million

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2
Q

How many photoreceptors do we have?

A

130 million

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3
Q

5 cell types found in the retina

A
  1. photoreceptors
  2. horizontal cells
  3. bipolar cells
  4. amacrine cells
  5. ganglion cells
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4
Q

What are the only 2 retinal cells that can generate AP?

A

amacrine, ganglion

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5
Q

3 layers of the retina cells

A
  1. inner layer (photoreceptors)
  2. outer/middle layer (horizontal, bipolar, amacrine)
  3. ganglion layer
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6
Q

Fovea is densely packed with ___. No ___.

A
  1. cones

2. rods

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7
Q

fovea is a blind spot under…

A

dim light

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8
Q

function of fovea

A

fine discrimination

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9
Q

blind spot =

A

where optic nerve exits the eye (no rods or cones)

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10
Q

photopigment in rods

A

rhodopsin

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11
Q

photopigment in cones

A

pigment molecules

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12
Q

how much rhodopsin do we have?

A

10^8

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13
Q

what are more sensitive, rods or cones?

A

rods (can be activated by single photon)

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14
Q

What kind of special synapse does photoreceptors have?

A

ribbon

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15
Q

What is the special SNARE protein associated with ribbon synapses?

A

RIBEYE (makes up 2/3 of ribbon volume)

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16
Q

Which ion is responsible for the continuous depolarization in the dark?

A

Na

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17
Q

What is the Vm of photoreceptors?

A

-40 mV

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18
Q

What happens when light hits photoreceptors?

A

Close Na channels on outer segment -> hyperpolarization -> less NT release

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19
Q

Relationship between cGMP and channels on photoreceptors

A
  • ↑ [cGMP] keeps Na channels open

* [cGMP] ∝ 1/intensity of light

20
Q

Which NT is released by photoreceptors?

A

glutamate

21
Q

Which NT is released by horizontal cells?

A

GABA

22
Q

Which NT is released by bipolar cells?

A

glutamate

23
Q

Which NT is released by amacrine cells?

A

DA or ACh

24
Q

Which NT is released by ganglion cells?

A

glutamate (mostly)

25
Q

Besides the typical NT, which other ones have been identified in the retina?

A

NO, BDNF

26
Q

receptor fields help with…

A

fine discrimination/contrast

27
Q

“on” ganglion cells =

A

center +, side -

28
Q

“off” ganglion cells =

A

center -, side +

29
Q

How many rods to 1 rod bipolar cell?

A

15-45

30
Q

How many cones to 1 cone bipolar cell?

A

5-20

31
Q

How many (cones or rods?) to 1 midget bipolar cell? What does it project to?

A

1 cone -> 1 midget bipolar cell -> specialized ganglion cell

32
Q

What is the only area of the brain with inhibitory glu receptors? Which glu R is this?

A

bipolar cells (mGluR6)

33
Q

What is it called when light hits the side of the center field?

A

annular illumination

34
Q

are H bipolar cells on or off center?

A

off

35
Q

Do H bipolar cells have excitatory or inhibitory mGluR?

A

excitatory

36
Q

Which bipolar cell do rods project to?

A

D bipolar cells

37
Q

How do rod bipolar cells typically interact with ganglion cells?

A

-> amacrine cells -> cone bipolar cells -> ganglion

38
Q

Functions of horizontal cells

A
  1. regulate bipolar cell response to annular illumination

2. spatial resolution (contrast)

39
Q

Horizontal cells are electrically coupled to ___ via ___

A

other horizontal cells via gap junctions

40
Q

Effect of light on horizontal cells

A
  • Light ⇒ photoreceptor hyperpolarize ⇒ horizontal cells hyperpolarize ⇒ ↓ GABA and NO release on surrounding photoreceptors ⇒ less inhibition ⇒ depolarization (small effect) (spread the response to light)
  • The ↑ photoreceptor activity ⇒ ↑ NT ⇒ stimulate inhibitory mGluR6 ⇒ D bipolar cells hyperpolarize
41
Q

What effect does NO secretion by horizontal cells have?

A

inhibit NT release from surrounding photoreceptors

42
Q

Why does half of the ganglion cells hyperpolarize, and half depolarize in response to light?

A

Due to D and H bipolar cells (membrane potential of ganglion cell will change in the same direction as the bipolar cell it’s connected to)

43
Q

Where does the connection go after ganglion cell?

A

-> lateral geniculate nucleus (LGN) cortex

44
Q

What is contralateral innervation?

A
  • Left visual field ⇒ right side of each retina ⇒ right LGN

* Right visual field ⇒ left side of each retina ⇒ left LGN

45
Q

What is the disease where you lose 1/2 the visual field on the same side in both eyes?

A

homonymous hemiopsia

46
Q

Damage to right cortex will cause blindness in ___ visual field

A

left

47
Q

Where is LGN located?

A

thalamus

CSB332 (10 decks)

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