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II. Neurophysiology and Perception > Bipolar Cells (M1) > Flashcards

Bipolar Cells (M1) Flashcards

1
Q

What channels open once an action potential reaches the axon terminal? 1. Which way do these ions then flow? 2

A
  1. Ca2+ channels

2. flow into cell

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2
Q

At rest, what is the [Ca2+] inside the cell? 1. Outside the cell? 2

A
  1. 0.05 uM

2. 2000uM (2mM)

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3
Q

What are the major differences in photoreceptor neurotransmission compared to normal neurotransmission?

A
  1. PR VGCC’c have low activation threshold (-40mV most open)

2. PR VGCC’s inactivate very slowly and remain open longer

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4
Q

Do photoreceptors release more neurotransmitters in the dark or light?

A

dark

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5
Q

What cells are ribbon synapses found in?

A
  1. rods
  2. cones
  3. retinal bipolar cells
  4. cochlear hair cells
  5. vestibular organ reeptors
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6
Q

What id the function of ribbon synapse?

A

shuttle synaptic vesicles to exocytotic sites like a conveyor belt

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7
Q

What is the cone synaptic terminal called?

A

cone pedicle

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8
Q

What are the two ways that horizontal and bipolar cells contact the cone?

A
  1. invaginations

2. basal junctions

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9
Q

How many invaginations are usually on one cone? 1. What is the typical arrangement of dendrites in this invagination? 2

A
  1. 12-25

2. 2 horizontal cell dendrites and 1 central bipolar dendrite

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10
Q

How many cones does each horizontal cell contact?

A

7-12

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11
Q

What kind of bipolar cells are usually at the flat synapses at the edge of an invagination? 1. Further away from the invagination? 2

A
  1. flat midget bipolar cell (fmb)

2. diffuse flat bipolar cell (fb or db)

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12
Q

What is the rod synaptic terminal called? 1. What kind of connections are on this terminal? 2

A
  1. rod spherule

2. one big invagination

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13
Q

What are the typical arrangements of dendrites in the rod invagination?

A

horizontal cells lateral and 2 bipolar dendrites centrally

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14
Q

How many rods can each rod bipolar cells receive input from?

A

15-50 rods

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15
Q

What are the two types of bipolar cells (and what is the physiology of each)?

A
  1. OFF bipolar (hyperpolarizes to light)

2. ON bipolar (depolarizes to light)

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16
Q

What kind of midget bipolar cells are usually in invaginating synapses with cones? 1. What kind are usually in flat synapses with cones? 2

A
  1. ON mb

2. OFF mb

17
Q

Where do OFF bipolars synapse within the inner plexiform layer?

A

inner nuclear layer

18
Q

Where do ON bipolars synapse within the inner plexiform layer?

A

closer to ganglion cell layer

19
Q

Are OFF bipolar cells sign-conserving or sign-inverting?

A

sign-conserving

20
Q

Are ON bipolar cells sign-conserving or sign-inverting?

A

sign-inverting

21
Q

What type of lighting (dark or light) does dumping glutamate on the retina mimick?

A

dark (depolarize OFF and hyperpolarize ON)

22
Q

What are the two types of ionotropic glutamate receptors (and do they depolarize or hyperpolarize)?

A
  1. Kainate/AMPA- type (depolarize)

2. NMDA-type (depolarize)

23
Q

What type of glutamate receptors are present mediate neurotransmission in OFF bipolar cells?

A

ionotropic Kainate/AMPA receptors

24
Q

What type of glutamate receptors are present mediate neurotransmission in ON bipolar cells?

A

metabotropic mGluR6 receptors (G-protein-coupled)

25
Q

What is the channel that connects mGluR6 to the depolarizing responses seen in ON bipolar cells? 1. What is the G-protein? 2

A
  1. TRPM1 channel

2. G(O) protein

26
Q

Does the TRPM1 channel open or close after mGluR6 is stimulated by glutamate via a G(O) pathway?

27
Q

What kind of bipolar cells are associated with rods?

A

ON bipolar cells only

28
Q

What are bipolar cells that only synapse with one cone called?

A

midget bipolar cells

29
Q

What portion of the eye has a more positive electrical charge? 1. How is this measured? 2

A
  1. front (cornea)

2. electrooculogram (EOG)

30
Q

Compared to the dark, when the lights are on is the difference in charge from the back of the eye to the front larger or smaller?

A

larger in light (at least 1.7x larger)

31
Q

What provides a measure of summed electrical activity in the retina in response to light stimuli?

A

electroretinogram (ERG)

32
Q

What is the reason for the a-wave of an ERG? 1. What does this represent? 2

A
  1. reduction in the dark current in PR’s stimulated with light
  2. functional integrity of photoreceptors
33
Q

What is the reason for the b-wave of an ERG? 1. What does this represent? 2

A
  1. depolarization of ON bipolar cells or changes in Mullers cells
  2. light responses in cells post-synaptic to photoreceptors
34
Q

What cells seem to drive the ERG?

A

changes in the outer retina

35
Q

How can cone contribution be minimized when taking ERG measurements?

A

use a dimmer light

36
Q

How can rod contribution be minimized when taking ERG measurements?

A

adapt subject with a brighter background light or stimulus that flickers at 30 Hz

II. Neurophysiology and Perception (24 decks)

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