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Y1 Principles > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

what is depolarisation?

A

when the membrane potential becomes less negative

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2
Q

what is hyperpolarisation?

A

the membrane potential becomes more negative

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3
Q

what causes a change in membrane potential?

A

ionic movements across the membrane

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4
Q

what two things determine the change in membrane potential?

A

direction of movement of the ion

charge on the ion

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5
Q

what direction is influx?

A

into the cell

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6
Q

what direction is efflux?

A

out of the cell

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7
Q

what drives passive movement of an ion through a channel?

A

its electrochemical gradient

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8
Q

when does movement of sodium ions occur?

A

in response to the opening of sodium selective channels on the cell membrane

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9
Q

what direction does sodium flow and why?

A

into a cell

its concentration and electrical gradients are inward

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10
Q

what is the value of the membrane potential and what represents this?

A

Vm = -70mV

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11
Q

what is the equilibrium potential for sodium?

A

Ena = +60mV

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12
Q

what is the driving force for sodium influx and when does sodium move into the cell?

A

Vm - Ena

when this is negative

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13
Q

what is Ina?

A

the current carried by sodium ions

Ina = gna(Vm-Ena)

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14
Q

what is Gna?

A

the sodium conductance

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15
Q

when does movement of potassium occur?

A

in response to the opening of potassium selective channels

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16
Q

which direction does K move in and why?

A

outwardly

its concentration gradient is outwards and greater than its inwards electrochemical gradient

17
Q

what is the equilibrium potential for potassium?

A

Ek = -100mV

18
Q

what is the driving force for K+ efflux?

A

Vm-Ek

moves outward when positive

19
Q

what are ion channels?

A

proteins that span the lipid bilayer forming pathways for selected ions

20
Q

what states do ion channels have and cycle between?

A

open (o) and closed (c)

21
Q

name two types of gated ion channels and state what opens them

A

voltage gated ion channels (opened by changes in membrane voltage)

ligand gated ion channels (opened when chemicals bind)

22
Q

what ion channels are responsible for the action potential in neurons?

A

voltage gated ion channels (VGICs)

voltage gated sodium and voltage gated potassium channels

23
Q

opening of which channel causes Vm to depolarise?

A

voltage gated sodium channels

24
Q

opening of which channel causes Vm to hyperpolarise?

A

voltage gated potassium channels

25
Q

what is an action potential?

A

a brief electrical signal in which the polarity of the membrane is momentarily reversed

26
Q

when is an action potential generated?

A

when the stimulus reaches threshold

27
Q

what does opening of a few sodium channels cause and what is this an example of?

A

the opening of further channels

positive feedback

28
Q

what does opening of a few potassium channels cause and what is this an example of?

A

closing of channels

negative feedback

29
Q

what happens to sodium channels during maintained depolarisation?

A

they enter a non-conducting inactivated state

30
Q

how does a sodium channel enter its closed state?

A

when repolarisation occurs

31
Q

what is the absolute refractory period?

A

no stimulus can elicit a second AP

all sodium channels inactivated

32
Q

what is the relative refractory period?

A

a very strong stimulus may be able to elicit a second AP

33
Q

what substance surrounds axons?

A

myelin

34
Q

what produces myelin in the PNS?

A

schwann cells

many surround a single axon

35
Q

what produces myelin in the CNS?

A

oligodendrocytes

one surrounds many axons

36
Q

what are oligodendrocytes and schwann cells?

A

types of macroglia

37
Q

is conduction faster in a myelinated axon or non myelinated axon?

A

myelinated

Y1 Principles (38 decks)

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