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Introduction to NeuroPhysiology > Action Potential > Flashcards

Action Potential Flashcards

1
Q

Action Potential

A

An action potential is a rapid sequence of changes in the voltage across a membrane. The membrane voltage, or potential, is determined at any time by the relative ratio of ions, extracellular to intracellular, and the permeability of each ion

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2
Q

Excitable Membrane

A

membrane capable of generating, maintaining, and conducting action potentials

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3
Q

Resting Membrane Potential

A

normal difference in charge across neuronal membrane

theoretically -70 Vm, but varies. Sits here due to electrical potential of K+ and Na+, and their relative permeabilities

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4
Q

Ion

A

atom/molecule with net electrical charge

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5
Q

Cation

A

Positive Ion

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6
Q

Anion

A

Negative Ion

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7
Q

Movement of Ions

A

Influenced by diffusion down the concentration gradient and electrical force.

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8
Q

ion channel

A

protein embedded in a membrane with 4-6 parts that create a polar pore that allow ions to pass across the neuronal membrane down the concentration gradient

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9
Q

ion selectivity

A

Ions can only pass through certain channels based on diameter of pore and polarity of internal R groups

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10
Q

ion pump

A

Use ATP to pump ions against concentration gradient

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11
Q

ion gating

A

Opening and closing of channels is determined by local environment in the cell. Eg local electrical charge

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12
Q

diffusion

A

Passive movement of a molecule from somewhere of high concentration to low concentration

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13
Q

concentration gradient

A

the gradual change in the concentration of solutes in a solution as a function of distance through a solution
established via ion pumps

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14
Q

electrical current

A

I measured in Amps
Movement of electrical charge

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15
Q

electrical potential

A

force exerted on a charged particle; reflecting difference in charge between anode and cathode

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16
Q

voltage

A

V measured in volts
electrical potential

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17
Q

electrical conductance

A

g measured in siemens(S)
relative ability of a charge to migrate from one area to another

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18
Q

electrical resistance

A

R measured in Ohms
relative inability of a charge to migrate
inverse of conductance (1/g)

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19
Q

Ohm’s law

A

I = gV
Current = conductance x electrical potential
Both g and v ≠ 0 for a current to be present

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20
Q

membrane potential

A

voltage across neuronal membrane at any point in time

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21
Q

microelectrode

A

glass rod with microneedle filled with conductive salt that is inserted into neurons to measure their potential difference

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22
Q

equilibrium potential

A

Eion
the electrical potential that balances an ionic concentration gradient so that the net movement of ions across the membrane = 0

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23
Q

ionic driving force

A

Where and how the ions are moving
(Vm-Eion)

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24
Q

Nernst Equation

A

takes into account temperature, charges of ion, ratio of concentration - check equation

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25
Q

Sodium Potassium Pump

A

Uses ATP to move 3 Na+ ions outside of the cell and 2 K+ ions into the cell
Consumes about 70% of all ATP in the brain

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26
Q

Calcium Pump

A

Pushes Ca2+ outside of cells to maintain a normal level via ATP

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27
Q

Goldman Equation

A

Accounts for relative permeability of ions, and does not account for leakage
See reference and practice

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28
Q

blood-brain barrier

A

blood vessels regulate movement and concentration of ions

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29
Q

rising phase

A

Na+ channels open so Sodium ions rush in as gNa increases. This leads mV to depolarise until approximately 40 mV

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30
Q

overshoot

A

when mV is > 0

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31
Q

falling phase

A

Rapid repolarization.
Na+ channels close and K+ channels open leading to potassium efflux

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32
Q

undershoot

A

Vm returns to resting potential

33
Q

hyperpolarization

A

Hyperpolarization is when the membrane potential becomes more negative at a particular spot on the neuron’s membrane

34
Q

depolarization

A

depolarization is when the membrane potential becomes less negative

35
Q

threshold

A

Miniumum mV for the channels of a certain proton to open

36
Q

absolute refractory period

A

the interval of time during which a second action potential cannot be initiated, no matter how large a stimulus is repeatedly applied

37
Q

relative refractory period

A

The relative refractory period is the interval of time during which a second action potential can be initiated, but initiation will require a greater stimulus than before.

38
Q

optogenics

A

Mutating brain cells so that ion channels become sensitive to light, allowing scientists to trigger action potentials with light

39
Q

Channel Rhodospin 2

A

ChR2

Mutated channels used to trigger light activation

40
Q

voltage clamp

A

membrane potential can be set a specific voltage to see if membranes will open

41
Q

voltage gated sodium channel

A

A sodium channel that cannot open without a voltage threshold being reached. Consist of 4 polypeptides, each made of 6 alpha helices. 4 helix senses voltage and twists to open the channel. After a time, a globular protein will block the channel so that the membrane potential can return to normal. Activate during the rising phase.

42
Q

patch clamp

A

Pipette used to isolate ion channel so that charge flow can be monitored and measured for one distinct channel

43
Q

channelopathy

A

diseases that develop because of defects in ion channels caused by either genetic or acquired factors

44
Q

tetrodotoxin

A

TTX
A toxin found in pufferfish that works by blocking Na+ channels.

45
Q

voltage gated potassium channels

A

Works like a voltages gated sodium channel.
Opens during falling phase

46
Q

Saltatory conduction

A

Some axons are wrapped in myelin sheaths to aid in the propogation of the action potential. Impulses only exist in the nodes between sheaths. This prevents the charge from diffusing, and speeds up the message

47
Q

spike-initation zone

A
48
Q

potential

A

seperation of electrical charge from across a membrane

49
Q

net differences in electrical charge in relation to membrane

A

measured right next to membrane

50
Q

capacitance

A

electrical charge gathers around membrane due to polarity on either side so in a way membrane holds a charge. This property is capacitance

51
Q

important ions

A

Na+, K+, Ca2+, Cl-

52
Q

Eion and Temperature

A

Proportional

53
Q

Eion and charge

A

Inversely Proportional

54
Q

Distribution of Ions

A

K+ inside
Na+ and Ca2+ outside

55
Q

Nernst at Body Temp

A

Only need respective concentrations

56
Q

Relative permeability of Na and K

A

Pk is 40x PNa

57
Q

Shakers

A

Fruit flys that were not put to sleep by ether vapours and instead shook. This was found to be due to a mutation in a specific type of potassium channel. This gene was then mapped and used to find the code for all other potassium channels, which helped understanding of selective permeability.

58
Q

Potassium Channels

A

A transmembrane polypeptide made of 4 subunits, whose R groups interact to create a pore loop that only allows K+ ions to pass through

59
Q

Scorpions

A

scorption toxin works by blocking potassium channels and binding to a site, this allowed the stretch of genes that allowed potassium specificity to be deciphered = 3D structure of potassium channel

60
Q

Mutations in Potassium Channel

A

Weaver mice - move weirdly and die early
epilepsy

61
Q

Lethal injections

A

administer sedative then overload body with K+ to induce cardiac arrest.

62
Q

Firing frequency

A

reflects magnitude of depolarizing current

63
Q

Saxitoxin

A

Toxin that works similarly to TTX. Found in forms of shellfish

64
Q

Batrachotoxin

A

Toxin that causes Na+ channels to open too long and early voltage wise

65
Q

A-Alpha Fibre

A

Myelinated, biggest and quickest fibre
Eg: Somatic Motor

66
Q

A-beta Fibre

A

Myelinated, big and quick fibre
Eg: Touch

67
Q

A-gamma Fibre

A

Myelianted, medium, and quickish fibre
eg: motor to intrafusal fibres of muscle spindles

68
Q

A-delta Fibre

A

Myelinated, medium, and quickish fibre
eg: pain and cold

69
Q

B Fibre

A

Myelinated, smallish, average speed fibre
eg: preganglionic autonomic

70
Q

C Fibre

A

Unmyelinated, small, slow fibre
eg: Pain, and Oflaction

71
Q

length constant

A

lambda in neuro

the rate of exponential decay of membrane voltage as a function of distance from the location where current is injected
review equation

72
Q

time constant

A

the product of the membrane resistance (rm) and membrane capacitance (cm)

73
Q

What increases the speed of an action potential?

A

Decreased Capacitance
Increased Axonal Diameter
Increased Myelination
Increased Internodal Distance

74
Q

Nodes of Ranvier

A

pecialized regions in the axonal membrane that are not insulated by myelin. Where Na+ channels are centralised and where AP propagate

75
Q

Multiple Sclerosis

A

Common symptoms include tiredness, vision problems and problems with walking or balance.
Caused by issues with axonal integrity and myelination damage (CNS), often caused by the immune system

76
Q

Guillian Barre Syndrome

A

Nerve damage beginning in hands and feet that will spread if untreated.
Caused by issues with axonal integrity and myelination damage( PNS).

77
Q

Motor Neuron Disease

A

Neurodegeneration of motor neurons

78
Q

Vincristine Neuropathy

A

Drug causes nerve damage

79
Q

Local Anaesthetic

A

Most common one is lidocaine, that works by upsetting AP by messing with Na+ channels

Introduction to NeuroPhysiology (6 decks)

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