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NEUR 301 > Electrophysiological Recording: Module 1.5 - 1.6 > Flashcards

Electrophysiological Recording: Module 1.5 - 1.6 Flashcards

1
Q

What does the current clamp technique measure?

A

Measurement of voltage while controlling applied current

Current usually clamped at a certain value

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2
Q

What does the voltage clamp technique measure?

A

Measurement of cell currents while controlling cell voltage

Voltage usually clamped at a certain value

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3
Q

How was the membrane potential recorded in the 1940s?

A

Used an intracellular recording electrode and an extracellular electrode. Injects different currents through membrane and records voltage through a voltage amplifier.

Used 2 sets of electrodes - one for recording, one for changing variable

Needed to puncture cells with electrodes - needed large cells able to withstand the puncture (could not use neurons other than squid axon).
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4
Q

What does Ohm’s law state?

A

States that the current between two points, through a resistor/conductor is directly proportional to the voltage acoross those two points.

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5
Q

Membrane potential was measured with electrodes inside and out of cells

What equation describes the membrane potential?

A

Vm = V(in) - V(out)

Membrane potential is a voltage difference. Value of exact voltage does not matter. Extracellular voltage assumed to be 0.

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6
Q

What type of current has porportional changes in voltage to current being applied in all cases?

A

Hyperpolarizing current

Depolarizing will eventually reach threshhold

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7
Q

To change the charge across the capacitor, current must flow ____ the capacitor.

A

To change the charge across the capacitor, current must flow through the capacitor.

Not current going through channels

Current is movement of charges towards and away from the capacitative plates

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8
Q

Given the equation below:

How is the change in voltage proportional to time?

A
This is because to change the charge across the membrane - current needs to flow through the capacitor which requires time.
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9
Q

If a membrane had only resistive properties:

How fast would a step pulse change the membrane potential?

A

It would change the membrane potential instantaneously

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10
Q

Given the membranes capacitive properties:

How fast would a step pulse change the membrane potential?

A

It would require time to achieve maximum change

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11
Q

When is the only time capacitative currents flow?

A

When the voltage across a capacitor is changing with time.

Capacitor being charged or discharged.

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12
Q

What technique can be used to see capacitive current?

A

Voltage Clamp

Spikes are Capacitive Current
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13
Q

Does a larger area of membrane take more or less time to fully charge?

A

More

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14
Q

The larger the area of membrane, the more ____ it can hold, and thus the greater its total _____.

A

The larger the area of membrane, the more charge it can hold, and thus the greater its toal capacitance.

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15
Q

What value can we obtain to help determine size of cell?

A

Capacitance

Can measure time it takes to charge but that value is also just a measure of capacitance.

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16
Q

Why are Xenopus Oocytes used to study neurology?

A
  • Can be made to Expressed any ion channel desired
  • Very Large Cells (Can withstand punctures)
  • Significant amount of current above basal noise levels
17
Q

Why do we use step pulses to study electrophysiology?

A

To seperate capacitive current with ion channel current.

Capacitive currents are at edges of recording

Amplifier subtracts Capacitive current
18
Q

Given that there is an AP (current) being generated:

How does the amplifier keep voltage clamped at set value?

Voltage Clamp Technique

A

Amplifier will inject current of equal an opposite sign to keep Vm the same.

Will display what it had to react to - Why it shows negative current for depolarization in voltage clamp technique.

19
Q

What are the different components of membrane current?

A
  • Capacitive Current
  • Ionic Current (Channels Conductance x Driving Force)
20
Q

What is 1 limitation of the study of ionic currents using voltage-clamp studies using electrodes?

A

Could only see macroscopic currents at the whole cell level. Does not have the ability to study individual ion channels.

21
Q

What technique can be used to evaluate single ion channel conductance?

A

Patch - Clamp Technique

22
Q

What is the Gigaseal and what are some of its benefits?

A

A microelectrode forms a high resistance seal with cell membrane using suction.

Benefits: Only need 1 electrode, does not need to puncture cell, noise due to current leaks is eliminated.

23
Q

What are the 4 configurations of the patch clamp technique?

A
  • Cell-Attached Patch
  • Whole-cell patch
  • Outside-out excised patch
  • Inside-out excised patch
24
Q

What are characteristics of the Cell-Attached configuration?

A
  • Can study unitary currents
  • Cell’s cytoplasm remains intact
  • Pipette Solution: extracellular
25
Q

What are characteristics of the Whole-cell configuration?

A
  • Can study Macroscopic currents
  • Gain access to cytoplasm
  • Pipette solution: intracellular
26
Q

What are characteristics of the Outside-out configuration?

A
  • Can study unitary currents
  • Can manipulate both sides (bath and pipette)
  • Pipette solution: intracellular
  • Useful for studying activation of neurotransmitter receptors and extracellular pharmacology.
27
Q

What are characteristics of Inside-out configuration?

A
  • Can study unitary currents
  • Can manipulate both sides - bath solution replaced with intracellular solution
  • Pipette solution: Extracellular
  • Useful when studying intracellular modulation of ion channels; (phosphorylation, ligands)
28
Q

What are the 3 gating stages of a Ion Channel?

A
  • Closed
  • Activated
  • Inactivated
29
Q

Based on the graph below:

What is the little hump at the start, what is the large downward spike, and what is the plateau at the end?

A
  • Remnant of Capacitive current
  • Large inward flux of Na(Action Potential)
  • Sodium channel Inactivation
30
Q

What type of receptos do AMPA and NMDA act on?

A

Glutamate receptors

31
Q

Does AMPA currents or NMDA currents inactivate?

A

AMPA currents inactivate

32
Q

What does the current through one ion channel look like?

A
2 states - Open and shut gating activity
33
Q

What is the equation that describes macroscopic from unitary current?

A
34
Q

Define Open probability(P0).

A

Is the fraction of total time that the channel is in the open state.

Closed State = 0 Current; Open State = Full unitary current

NEUR 301 (8 decks)

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