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Introduction to NeuroPhysiology > Action Potential > Flashcards

Action Potential Flashcards

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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
Sodium Potassium Pump
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
26
Calcium Pump
Pushes Ca2+ outside of cells to maintain a normal level via ATP
27
Goldman Equation
Accounts for relative permeability of ions, and does not account for leakage See reference and practice
28
blood-brain barrier
blood vessels regulate movement and concentration of ions
29
rising phase
Na+ channels open so Sodium ions rush in as gNa increases. This leads mV to depolarise until approximately 40 mV
30
overshoot
when mV is > 0
31
falling phase
Rapid repolarization. Na+ channels close and K+ channels open leading to potassium efflux
32
undershoot
Vm returns to resting potential
33
hyperpolarization
Hyperpolarization is when the membrane potential becomes more negative at a particular spot on the neuron's membrane
34
depolarization
depolarization is when the membrane potential becomes less negative
35
threshold
Miniumum mV for the channels of a certain proton to open
36
absolute refractory period
the interval of time during which a second action potential cannot be initiated, no matter how large a stimulus is repeatedly applied
37
relative refractory period
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
optogenics
Mutating brain cells so that ion channels become sensitive to light, allowing scientists to trigger action potentials with light
39
Channel Rhodospin 2
ChR2 Mutated channels used to trigger light activation
40
voltage clamp
membrane potential can be set a specific voltage to see if membranes will open
41
voltage gated sodium channel
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
patch clamp
Pipette used to isolate ion channel so that charge flow can be monitored and measured for one distinct channel
43
channelopathy
diseases that develop because of defects in ion channels caused by either genetic or acquired factors
44
tetrodotoxin
TTX A toxin found in pufferfish that works by blocking Na+ channels.
45
voltage gated potassium channels
Works like a voltages gated sodium channel. Opens during falling phase
46
Saltatory conduction
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
spike-initation zone
48
potential
seperation of electrical charge from across a membrane
49
net differences in electrical charge in relation to membrane
measured right next to membrane
50
capacitance
electrical charge gathers around membrane due to polarity on either side so in a way membrane holds a charge. This property is capacitance
51
important ions
Na+, K+, Ca2+, Cl-
52
Eion and Temperature
Proportional
53
Eion and charge
Inversely Proportional
54
Distribution of Ions
K+ inside Na+ and Ca2+ outside
55
Nernst at Body Temp
Only need respective concentrations
56
Relative permeability of Na and K
Pk is 40x PNa
57
Shakers
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
Potassium Channels
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
Scorpions
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
Mutations in Potassium Channel
Weaver mice - move weirdly and die early epilepsy
61
Lethal injections
administer sedative then overload body with K+ to induce cardiac arrest.
62
Firing frequency
reflects magnitude of depolarizing current
63
Saxitoxin
Toxin that works similarly to TTX. Found in forms of shellfish
64
Batrachotoxin
Toxin that causes Na+ channels to open too long and early voltage wise
65
A-Alpha Fibre
Myelinated, biggest and quickest fibre Eg: Somatic Motor
66
A-beta Fibre
Myelinated, big and quick fibre Eg: Touch
67
A-gamma Fibre
Myelianted, medium, and quickish fibre eg: motor to intrafusal fibres of muscle spindles
68
A-delta Fibre
Myelinated, medium, and quickish fibre eg: pain and cold
69
B Fibre
Myelinated, smallish, average speed fibre eg: preganglionic autonomic
70
C Fibre
Unmyelinated, small, slow fibre eg: Pain, and Oflaction
71
length constant
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
time constant
the product of the membrane resistance (rm) and membrane capacitance (cm)
73
What increases the speed of an action potential?
Decreased Capacitance Increased Axonal Diameter Increased Myelination Increased Internodal Distance
74
Nodes of Ranvier
pecialized regions in the axonal membrane that are not insulated by myelin. Where Na+ channels are centralised and where AP propagate
75
Multiple Sclerosis
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
Guillian Barre Syndrome
Nerve damage beginning in hands and feet that will spread if untreated. Caused by issues with axonal integrity and myelination damage( PNS).
77
Motor Neuron Disease
Neurodegeneration of motor neurons
78
Vincristine Neuropathy
Drug causes nerve damage
79
Local Anaesthetic
Most common one is lidocaine, that works by upsetting AP by messing with Na+ channels

Introduction to NeuroPhysiology (6 decks)

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