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Neuroscience > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

describe an action potential

A
  • resting membrane potentials = maintained by lead K+ currents
  • when membrane potential reaches threshold voltage gated sodium channels are activated
  • more voltage gated sodium channels activated
  • sodium channels inactivate and slower voltage gated potassium channels activated
  • voltage gated potassium channels can cause an overshoot = after hyper polarisation (AHP)
  • resting membrane potential re established
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2
Q

CA1 pyramidal neurons

A

hippocampus
glutamatergic principle cell
Afferents =
* CA3 pyramidal cells
* entorhinal cortex
* various hippocampal GABAergic neurons

Efferents =
* subiculum
* entorhinal cortez
* prefrontal cortex
* variosu GABAergic interneurons

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3
Q

Orient-Lacunosum molecular interneurons

A

GABAergic interneurons
Afferents
*hippocampal pyramidal cells
*medial septum
* other interneurons

Efferents
*distal dendrites of CA1 pyramidal neuorns
*other interneurons

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4
Q

how do differences in AP waveform come about

A

different threshold depending on properties of sodium channels

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5
Q

does CA1 or O-LM have a more hyperpolairsed (lower) threshold

A

CA1 threshold is lower than O-LM

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6
Q

explain the voltage gated sodium channel chain reaction

A
  • positive sodium flow into cell
  • results in a region of positive charge across the membrane
  • local depolarisation activates nearby sodium channels causing more positively charge sodium ions to Flow into cell
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7
Q

when is the chain reaction triggered

A

Action potential threshold
absolute values varies depending on properties of sodium channel

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8
Q

what are the alpha subunit subtypes of a CA1-PN

A

rNav1.6,1.2
2 types of cottage gates sodium channels

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9
Q

what are the alpha subunit subtypes of interneurons (OLM)in CA1 in hippocampus

A

rNav1.1
one type of voltage gated sodium channel

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10
Q

what do voltage gate sodium channels consist of

A

alpha subunit
(transmembrane domains and linkers)
beta subunit

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11
Q

where does the difference between sodium ion channels lie

A

in the alpha subunit

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12
Q

what is the V1/2

A

membrane potential when half sodium channels are open

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13
Q

V1/2 for a NaV1.1 interneuron

A

-20mV

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14
Q

V1/2 for a NaV1.2 pyramidal neuron

A

-24 mV

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15
Q

V1/2 for a naV1.6 pyramidal neuron

A

-29 mV

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16
Q

Why might one EPSP trigger an AP in the presynaptic cell and not the postsynaptic cell?

A

because the postsynaptic cell might have a higher (more depolarised) threshold.

17
Q

what control burst firing

A

afterpolarisation

18
Q

what is burst firing

A

the frequency of AP firing slows down with time

19
Q

what is burst firing

A

the frequency of AP firing slows down with time

20
Q

afterpolarisation

A

controls burst firing
after depolarising potentials are slower and smaller than AP

21
Q

how can afetrpolarisation trigger another AP

A

if the after depolarisation is sufficiently long or large = trigger another AP

22
Q

ionic mechanisms underlying large After hyper polarisation in GABAergic interneurons

A
  • both pyramidal neurons and interneurons express a range of different voltage gated potassium channels
  • interneurons express high levels of Kv3 subtypes
  • fast activating, fast deactivation channels are activates at very depolarised potentials
    –> produce the large post-spike AHP
    –> enable very fast repolarisation of the AP
    –> maximises quick recovery of resting conditions of membrane
23
Q

why does a larger AHP contribute to sustained high frequency firing

A

AHP controls a continuous high frequency firing

24
Q

voltage gated sodium channels in resting state

A

closed

25
Q

voltage gates sodium channels after depolarising stimulus

A

polarity of membrane changes
gates are opened

26
Q

inactivation gate role

A

closes pore from the inside
inactivated channel
can’t be activated
if opened for a long time

27
Q

what does recovery from inactivation depend on

A
  • time = takes time for channels to move from inactivated to closed state
    channel will open again proportionally to the amount of time passed since the first depolarising stimulus
  • voltage steps - depolarising at a more positive level it will show a smaller current on the second pulse
28
Q

when do channels move from inactive to closed state

A

depolarisation

29
Q

what is the recovery period

A

channels move from inactive to closed state

30
Q

what does re depolarising at a more positive (depolarised) level do to the second pulse

A

smaller current

31
Q

if APs in OLM cells are narrower …

A

less inactivation
sodium channels recover from inactivation faster
promotes high frequency repetitive AP firing

32
Q

is APs in OLM cells have large AHP which pushes the membrane to more hyperpolarsed potentials

A

faster recovery from inactivation
sodium channels recover from inactivation faster
promotes high frequency repetitive AP firing

Neuroscience (14 decks)

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