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BPK 306 > Passive And Action Potentials > Flashcards

Passive And Action Potentials Flashcards

1
Q

Conductance equation

A

I = gV

Derived from ohms law V = IR

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2
Q

What does conductance show

A
  • how many channels are open
  • how many channels there are
  • how much current the channel can pass
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3
Q

What does a change in current cause

A

Change in membrane potential (voltage)

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4
Q

How can a stimulus be applied (current)

A
  • result of another neuron (at synapse)
  • spontaneous (pacemaker cells)
  • introduced to the system using electrophysiology techniques
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5
Q

What is cable theory, what does it predict

A

Propagation can be predicted
- models axons and dendrites as cylinders with RC circuits

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6
Q

What does a depolarizing current graph look like

A

Rectangle upwards

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7
Q

How does membrane potential change with increasing distance from current electrode- EPSP

A

Decrease in amplitude with distance- not regenerated and ions diffuse

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8
Q

How does membrane potential change with increasing distance from current electrode- AP

A

AP are regenerative. Threshold reached, all or none signal

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9
Q

How is a passive response formed

A

Stimulus opens ion channels and ions diffuse to spread potential (no voltage gated channels)

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10
Q

Passive properties in neurons

A
  • membrane capacitance
  • membrane resistance
    — both affected by myelin
  • internal resistance ( intracellular longitudinal resistance along axons and dendrites)
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11
Q

What do the passive properties in neurons determine

A

Determine how far a passive potential generated at a dendrite will travel and whether the passive potential will result in an AP at axon hillock

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12
Q

How are passive potentials propagated

A

Diffusion (no ion channels)

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13
Q

Why does passive potential lag

A

Membrane capacitance and time it takes for ions to rearrange

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14
Q

What determines voltage response

A

Membrane resistance and membrane capacitance (shape and magnitude)

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15
Q

Voltage response wave looks like

A

Rounded squares

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16
Q

How fast can current and voltage change

A

Current instantaneous
Voltage lags- ions rearrange and membrane capacitance

17
Q

When threshold is reached. What channels open

A

Nav

18
Q

Outward current is ___ charge efflux
Inward current is ____ charge influx

A

Positive
Current is the flow of positive charge

19
Q

What does a higher membrane capacitance do to ion rearrangement

A

Charges take longer to rearrange

20
Q

What initiates passive potentials

A

Ion channels (nAC)

21
Q

What is the length constant (upside down y)

A

Distance at which the potential is 1/e of its original value
(voltage change falls exponentially with distance from stimulation site)

22
Q

Be able to compare passive and action potentials

A

Pg 8

23
Q

What kind of responses can dendrites produce

A

Passive potentials (that are summed)
Dendritic Spikes- active potential

24
Q

What percent of voltage is length constant from initial amplitude

A

37%

25
Q

What is the length constant equation

A

Y - sqrt Rm/Ra (axial = internal)

26
Q

What does an amplitude vs distance graph of passive potential look like

A

Middle has highest amplitude and is starting point of potential (current injection). Drops off exponentially on both sides as distance increases looks like a ^

27
Q

How does increasing neuron diameter impact Rm, Ra, length constant y

A

Rm decreases- more plasma membrane, more leak channels
Ra decreases- larger diameter allows faster propagation inside neuron
Ra reduced by a greater factor than Rm- pir^2 bigger impact than 2pi*r (change r)
Y increases

28
Q

What is conduction dependent on

A

Length and diameter (geometric factors)
- inversely proportional to length
- directly proportional to CSA

29
Q

Explain steps of AP curve and what ions contribute

A

Pg 13

30
Q

How to measure Vm

A

Internal electrode and extra cellular reference electrode

31
Q

How to measure electrical signals in neurons

A

Electrophysiology techniques

32
Q

What is important for unidirectional AP conductance? What is the term called

A

Neuronal backpropagation
1. Na channel inactivation
2. Increased Pk - slow K channel activation
- refractory period link

BPK 306 (18 decks)

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