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Neuroscience > Electrophysiology > Flashcards

Electrophysiology Flashcards

1
Q

How is resting potential established?

A

3Sodium/2Potassium ATPase pumps in the membrane bring potassium in
Potassium flows out down concentration gradient through leaky channels
Anions cannot follow, electrical gradient forms
Electrochemical equilibrium

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2
Q

3 Models that can be used to study electrophysiology

A

Whole animal models
Acute brain slices
Dissociated neuronal cell cultures

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3
Q

What are dissociated neuronal cell cultures?

A

Neuronal stem cells, typically from a rat, are grown in vitro into an artificial synaptic network

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4
Q

Pros/Cons of dissociated neuronal cell cultures

A

Easy to record from
Difficult/impossible to replicate exact in vivo conditions
Haven’t been developed in a normal physiological environment

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5
Q

What are acute brain slices?

A

Slice of brain 300-400 microns thick

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6
Q

Pros/Cons of acute brain slices

A

Can be taken at any developmental stage

Difficult/impossible to replicate exact in vivo conditions

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7
Q

Pros/Cons of whole animal models

A

Expensive
Tight regulations on living conditions
Technically very difficult to record from
Can provide in vivo results - most accurate
All circuits of brain fully intact

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8
Q

Two types of equipment for recording electrical activity?

A

Patch pipette - wide tip, sucks up cell membrane, cytoplasm be comes continuous with inside of pipette
Sharp electrode - pokes hole in cell, filled with liquid that matches the cell potential

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9
Q

What is Ohms law (and units)?

A

Voltage (V) = Current (Amps) X Resistance (Ohms)

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10
Q

What is a current clamp recording?

A 
Current is injected into the cell 
Injection of negative current leads to hyperpolarisation
Change in voltage is proportional 
Record the voltage
Used to calculate resistance
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11
Q

What affects resistance?

A

Resistance is affected by the ion channels in the membrane, and whether they are open or closed
When applying a drug that opens ion channels, resistance will decrease

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12
Q

What is an EPSP?

A

EPSP = Excitatory Post Synaptic Potential
It is the (positive) membrane potential change caused by cation influx/depolarisation
Measured using a current clamp recording

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13
Q

What is a single unit recording?

A

Using a single electrode to record the fieldEPSP from the extracellular space of a group of neurons
Records the overall result of many different neurons at once

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14
Q

Pros/cons of a single unit recording

A

Can be recorded in vivo
Records an ‘average response’ from many neurons, so these is less variation
No disruption of cell contents
Cannot identify which neurons are influencing the fEPSP
Neurons that are closer to the electrode will have stronger influence

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15
Q

What are multi-electrode recordings?

A

Record the fEPSP using multiple electrodes positioned at different points
Eliminates the effect of neurons closer to the electrode having more effect

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16
Q

What is functional imaging?

A

A way of recording/measuring neuronal activity by measuring the calcium influx

17
Q

How does functional imaging work?

A

The gCaMP protein is applied to cells
When 4 calcium ions bind to the gCaMP protein, it undergoes a conformational change which causes it to become fluorescent

18
Q

3 methods of measuring neuronal activity

A

Single Unit recording
Multi electrode recording
Functional imaging

19
Q

What type of graph is used to analyse an action potential?

A

Phase plane plot

20
Q

What are the x and y axes of a phase plane plot?

A 
x = voltage (mV)
y = 1st derivative of the AP
21
Q

What 4 things can a phase plane plot tell you (and at which point on the graph are they)?
Draw this out

A

Top point = Maximum rate of rise
Furthest right = AP peak
Lowest point = Maximum rate of fall
Magnitude of the after hyperpolarisation = distance between the lines on the left

22
Q

What is v1/2 activation and what does it tell you?

A

Half maximal activation voltage
Lower v1/2 activation indicates that channels become activated at a more hyperpolarised (lower) action potential threshold - more excitable

23
Q

3 sodium channels present in the hippocampus, which neuron type are they present on and what is the v1/2 activation?

A

Nav1.1, Interneurons, -20mV
NaV1.2, Pyramidal, -24mV
NaV1.6, Pyramidal, -29mV

24
Q

What is the structure of a sodium channel?

A

Large alpha subunit
Properties are modulated by forming covalent bonds with B1 and B2 subunits
Modulated by phosphorylation
‘Ball and chain’ plug

25
Q

3 states of sodium channel activation

A
  1. Closed (can be activated)
  2. Open
  3. Inactive (cannot be activated until shifted back to closed state)
26
Q

Cycle of sodium channel activation

A
  1. Channel is closed at resting potential
  2. AP arrives, depolarisation causes conformational change, channel opens
  3. Channel quickly shifts to inactivated state
  4. Following hyperpolarisation, the channel shifts back into the closed state
27
Q

What is the advantage of having a greater after-hyperpolarisation?

A

Can fire again more quickly

28
Q

What is an after-depolarising potential?

A

Occurs in CA1 neurons
Instead of an afterhyperpolarisation, there is another mini depolarisation following the AP
If it crosses the AP threshold again, triggers a high frequency burst of APs

29
Q

What is intrinsic plasticity?

A

The modulation of the electrical properties of a neuron, by changing the ion channels

30
Q

Give an example of how intrinsic plasticity can be used to modulate CA1 neurons

A

DHPG is a synthetic mGlu group 1 receptor agonist
Can be applied to CA1 pyramidal neurons to make the after-depolarisation potential smaller, so it is less likely to pass the AP threshold
Reduces the probability of a high frequency burst

31
Q

What are the differences between the APs of a CA1 pyramidal neuron and a OLM interneuron?

A

CA1 has faster rate of rise
CA1 has higher peak
OLM has faster rate of fall
OLM has larger after-hyperpolarisation

32
Q

What is the equation for resistance?

A

Resistance = Change in voltage/Change in current

33
Q

What is an EPSC?

A

EPSC = Excitatory Post Synaptic Current
It is the (negative) injection of current by the amplifier required to counteract the positive membrane potential cause by cation influx
Measured using a voltage clamp recording

34
Q

What is voltage?

A

The separation of charge between the inside and the outside of the cell

35
Q

What is a voltage clamp recording?

A

Voltage fixed at a particular membrane potential
Used to study the underlying currents
An EPSP causes an EPSC, in order to counteract the membrane depolarisation

Neuroscience (12 decks)

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