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block 5 Anna > block 5 lecture 8 action potentials > Flashcards

block 5 lecture 8 action potentials Flashcards

1
Q

what is an action potential?

A

rapid change in electrical charge across a plasma membrane

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2
Q

where do action potentials occur?

A

neurons muscle fibers and endocrine cells

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3
Q

what is the cell body of a neuron also called?

A

soma

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4
Q

what is the main input structure on a neuron?

A

dendrites

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5
Q

what is the output structure of a neuron

A

axon

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6
Q

what does myelination do?

A

provides insulation

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7
Q

what is the region between soma and axon called?

A

axon hilock

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8
Q

what may the signals be arriving at the synapse?

A

excitory or inhibitory

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9
Q

what are the signals called travelling in dendrites?

A

electrotonic potentials

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10
Q

when travelling in dendrites what is the response called and what does this mean?

A

graded response, response is proportional to the stimulus

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11
Q

what happens to the negative and positive electrotonic potential

A

they are summed in the soma

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12
Q

what does the excitation have to be above to get an action potential?

A

threshold

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13
Q

what kind of spread of action potential do you get down the axon?

A

non decramental

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14
Q

what is the membrane potential?

A

difference of electrical potential between the inside and outside of the cell

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15
Q

what voltage is the resting potential?

A

-70

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16
Q

what is the threshold potential? (value)

A

-55

17
Q

what do ion channels do?

A

selectively transfer ions

18
Q

what are the 3 types of ion channels in maintaining resting potential?

A

leak ion channels, voltage gated ion channels, ligand gates ion channels

19
Q

what is the active tranport in an action potential?

A

sodium potassium pump

20
Q

how does the sodium potassium pump work?

A

3 sodium and ATP binds to pump
hydrolysis of ATP phosphrylates the pump causing it to change in shape
this releases sodium ions and allows two potassium ions to bind
release of the phosphryl group releases potassium into the cystol

21
Q

what are the three factors of resting potential?

A

low protein permeability
sodium potassium pump
high potassium permeability through leak channels

22
Q

limitations of the nerst equation?

A

one ion
only considers valance and conc gradient
dosent consider permeability

23
Q

what are the 4 stages of an action potential?

A

resting state
depolarizing phase
repolarising phase
undershoot

24
Q

during the resting state what is happening?

A

-70mv, all voltage gated sodium and potassium channels closed

25
Q

during the depolarization phase what is happening?

A

-55 threshold is reached, voltage gated sodium ion channels open

26
Q

during the repolarization phase what is happening?

A

+40mv, voltage gated potassium ion channels open, sodium voltage gated channels close

27
Q

during the undershoot what is happening?

A

-80mv, potassium channels slowly close

28
Q

after the threshold what is the strength of the stimulus encoded by?

A

frequency of action potential

29
Q

how is the action potential conducted in an unmyelinated axon?

A

sodium entry at axon hiloclk locally depolarises axon, adjacent axon depolarised

30
Q

how is one way conduction of an action potential ensured?

A

sodium channels are inactivated due to the refractory period

31
Q

how are action potentials conducted in a myelinated axon?

A

the myelin sheath prevents leakage, sodium and potassium channels are concentrated at the nodes of ranvier, saltatory conduction

32
Q

what does the speed of conduction depend on?

A

diameter and myelination

33
Q

what does the diameter change during action potential conduction?

A

larger axon faster conduction

34
Q

what are C axons?

A

smaller than a micron and unmyelinated

35
Q

what is MS?

A

autoimmune, T cells attack the myelin sheath

36
Q

what is tetrodotoxin?

A

toxin produced by symbiotic bacteria in pufferfish that block s sodium channels

37
Q

what do local anesthetic do?

A

block voltage gated sodium ion channels, prevent Adelta and C fibers which transmit pain

38
Q

what are the types of local anesthetics?

A

esters: cocain
amides: lidocain

39
Q

what can prolong local anesthetics?

A

vasoconstrictors

block 5 Anna (16 decks)

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