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Neuroscience > Action Potential > Flashcards

Action Potential Flashcards

1
Q

Where does an AP initiate?

A

in axon hillock

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2
Q

After initiation, where does an AP propagate?

A

AWAY from cell body/soma

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3
Q

What type of pumps establish and maintain membrane potential?

A

ATP dependent

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4
Q

Which postsynaptic potentials dictate what happens at the post synaptic membrane potential?

A

IPSPs and EPSPs

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5
Q

What is the Goldman equation?

A

Em = 58 log (Pk[Ko] + Pna[Nao] + Pcl[Clin] / Pk[Kin] + Pna[Nain] + Pcl[Clo])

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6
Q

What causes a change in Vm?

A
  1. by changing internal/external ionic conc.
  2. by changing relative permeability of ions across the plasma membrane
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7
Q

What conc. has the greatest permeability and influence on Vm?

A

K+

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8
Q

How are ionic permeabilities changed?

A
  1. ligand gated
  2. voltage gated
  3. nucleotide gated; 2nd messenger systems
  4. inward rectifier “leak” channels
  5. mechanosensitive gated (stretch)
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9
Q

What are examples of ligand gated channels?

A

(GABA, Glu, 5HT)

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10
Q

What are examples of voltage gated channels?

A

Na+ and K+

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11
Q

What are examples of nucleotide gated channels?

A

cAMP and cGMP

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12
Q

What are the 5 types of voltage gated channels?

A
  • Na+
  • Ca+
  • K+
  • Cl-
  • H+
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13
Q

What types of ion channels play a major role in pH/homeostasis?

A

proton gated

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14
Q

What channel opens after depolarization and re-polarizes the membrane?

A

K+

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15
Q

What happens when Na+ channels open?

A
  • membrane potential depolarizes
  • increased flow of ions
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16
Q

What happens when K+ channels open?

A

membrane is repolarized

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17
Q

What happens AFTER K+ channels open?

A
  • Na channels change conformation and inactivate
  • increased Pna is shut down
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18
Q

What are the 3 conformational states following a depolarization?

A
  • open: “a” or “m” gate
  • inactive: “i” or “h” gate
  • closed
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19
Q

When Pk remanis high, what happens to Vm?

A

becomes transiently more negative than the baseline resting Vm

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20
Q

What is the response of K+ relative to Na+ channel during an outward current?

A

delayed

21
Q

What region has a voltage sensor on it and what is its function?

A

S4: sense changes in Vm and move in repsonse to the changes

22
Q

Where is ion selectivity located in regards to the molecular structure of the channels?

A

within the pore itself

23
Q

What is the trend of Pna and Pk in neuronal AP?

A
  • rapid increase in Pna
  • slower, more stable increase in Pk
24
Q

Slower activation of what channel contributes to repolarization?

A

K+

25
Q

What does the activation of K+ channels lead to?

A
  • negative feedback loop
  • hyperpolarization that decreases probability of activating more channels
26
Q

AP will NOT fire if what?

A

Vm is under threshold

27
Q

What type of phenomenon is AP?

A

all or none

28
Q

Na channels can be blocked by what?

A

TTX and riluzole

29
Q

What are the 2 factors influencing length constant?

A

membrane and internal resistance

30
Q

What is high membrane resistance?

A
  • very little ions are leaking out
  • directly proportional to length constant
31
Q

What is low internal resistance?

A
  • less ions within the cell
  • inversely proportional to length constant
32
Q

What is the length constant?

A

distance it takes to reach 37% of Vmax

33
Q

What is absolute refractory period?

A

2nd AP CANNOT fire because Na channels can’t be reactivated in open/inactivated state (peak in graph)

34
Q

What is relative refractory period?

A
  • greater depolarization is required for an AP to fire (flatter line in graph)
  • active K+ channels move membrane away from threshold potential
35
Q

What is the rate limiting event for AP propagation?

A

time needed to charge the membrane to change Vm

36
Q

What is the formula to charge the membrane?

A

t= Rm * Cm

37
Q

How does myelination increase the conduction velocity?

A

by increasing membrane resistance

38
Q

What is the relationship between the myelination of an axon and its conduction velocity?

A

directly proportional

39
Q

What can affect conduction velocity?

A

myelination and size of axon

40
Q

What is capacitance?

A

ability to hold charges on the membrane

41
Q

When does capacitance decrease?

A

when myelin membrane is added

42
Q

What is saltatory conduction?

A
  • propagation along myelinated axons
  • AP jumps from one node to the next
43
Q

What happens during saltatory conduction?

A
  1. myelination increases membrane resistance
  2. decreases membrane capacitance
  3. decreases membrane permeability
  4. increase conduction velocity
  5. length constant increased
44
Q

How does increasing conduction velocity affect unmyelinated axons?

A
  • slower conduction
  • local current flow (electrotonic conduction)
45
Q

How does increasing conduction velocity affect myelinated axons?

A
  • faster conduction
  • saltatory conduction
  • AP jumps from node to node
46
Q

What is multiple sclerosis?

A

autoimmune, degenerative disease of axon demyelination

47
Q

What affect does axonal demyelination have on AP conduction velocity?

A

causes it to decrease

48
Q

What are the key concepts of AP propagation?

A
  1. depolarization attenuates as it moves down the axon
  2. peak membrane potential during an AP remains consistently depolarized
  3. action propagation takes time to charge membrane
  4. myelination increases conduction velocity
49
Q

As depolarization moves down the axon, this is caused by what?

A

membrane and interaxonal resistance

Neuroscience (9 decks)

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