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Cellular Neuroscience > Brain Electrophysiology I & II > Flashcards

Brain Electrophysiology I & II Flashcards

1
Q

what were the results of the Hodgkin and Huxley (1939) model?

A

1) axons at rest are electrically polarized
2) -60mV inside v.s the outside

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2
Q

what were the methods of the Hodgkin and Huxley model?

A

voltage clamp experiments and by varying extracellular Na and K concentrations

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3
Q

what is an action potential?

A

when polarization of the membrane is removed (due to depolarization)

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4
Q

what is hyperpolarization?

A

a rapid swing in membrane potential to more negative values following depolarization

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5
Q

what is after-polarization?

A

a period of increased polarization

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6
Q

what forces determine the passive distribution of ions?

A

electrical and thermodynamic forces

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7
Q

how do ions move down their concentration gradients?

A

via ion channels or diffusion

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8
Q

what does the movement of ions result in?

A

redistribution of electrical charge (voltage gradient), which can cause either hyperpolarization or depolarization

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9
Q

what is the reversal potential?

A

the membrane potential at which the net current flips direction

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10
Q

what is the equilibrium potential?

A

the membrane potential at which there is not net movement of ions, which is basically a balance between voltage and concentration gradients

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11
Q

how can the equilibrium potential be calculated?

A

Nernst Equation

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12
Q

what are the ions that contribute to the resting membrane potential?

A

Na, K, Cl
the membrane is not at equivalent potentials for one ion (as they all contribute to the resting potential

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13
Q

what do ion pumps do?

A

maintain concentration gradients

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14
Q

how do ion pumps maintain the concentration gradient?

A

by actively transporting ions

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15
Q

what is one example of an ion pump?

A

the Na/K ATPase pump

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16
Q

how is the Na/K ATPase pump get stimulated?

A

by increased of intracellular Na

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17
Q

what does the Na/K ATPase pump move in and out?

A

Na out and K in

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18
Q

the Na/Ca2 exchanger is an example of an…

A

ion pump

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19
Q

a chloride-bicarbonate exchanger is an example of an…

A

ion pump

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20
Q

which ions increase in conductance during an action potential?

A

Na and K

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21
Q

Na and K conductance causes the membrane to become more positive or negative?

A

positive, in order to reach depolarization

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22
Q

what happens after an action potential?

A

the membrane potential re-polarizes (becomes more negative) than resting (hyperpolarization)

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23
Q

what is a transient inward current?

A

a more positive charge inside of the cell

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24
Q

what happens in the giant squid action when you increase the voltage from -60mV to 0mV?

A

produces a transient inward current and it is followed by a sustained outward current

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25
Q

what is a pharmacological blockade?

A

drugs or substances that inhibit or block specific physiological or biochemical processes in the body

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26
Q

what does tetradotoxin (TTX) block?

A

Na channels

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27
Q

when you increase the membrane potential in the presence of TTX, what ion current increases?

A

K only

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28
Q

what does tetraethylammonium (TEA) block?

A

K channels

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29
Q

when you increase the membrane potential in the presence of TEA, what ion current increase?

A

Na only

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30
Q

how do K channels open?

A

via their voltage sensitive gates and depolarization

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31
Q

how do K channels close?

A

via depolarization, which leads to deactivation

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32
Q

what are the different states that a Na channel can be in throughout an action potential?

A

activated, deactivated, and inactivated

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33
Q

what is the inactivation state of the Na channel?

A

when the channel is inactive despite maintained depolarization

34
Q

what is “deinactivation”?

A

the removal of the inactivation state of the Na channel

35
Q

what Na gate opens during depolarization?

A

activation gates

36
Q

what Na gates close during depolarization?

A

inactivation gates

37
Q

what Na gate closes during repolarization?

A

activation gates

38
Q

what Na gates open during repolarization?

A

inactivation gates

39
Q

what is the action potential threshold?

A

-55mV

40
Q

how does the movement of Na ions depolarize the axon?

A

by moving more Na inside, this opens more Na channels

41
Q

what are the two voltage-sensitive processes that Na channels display?

A

1) activation -> deactivation
2) inactivation -> deinactivation

42
Q

what is propagation?

A

initiation

43
Q

in what two places can action potentials start?

A

1) the axon initial segment
2) the axon hillock

44
Q

where does the action potential move (2 directions)?

A

1) propagates down the axon
2) antidromically backwards to the dendrites

45
Q

what is antiromically?

A

the propagation of an action potential in the opposite direction to the normal flow

46
Q

what is the threshold for AP generation in the initial segment?

A

low threshold

47
Q

what is the density of Na channels in the initial segment?

A

high density

48
Q

how can the speed of action potentials be affected?

A

by myelination

49
Q

how do unmyelinated axons move the action potential?

A

by depolarizing adjacent regions of the membrane

50
Q

how do myelinated axons move the action potential?

A

by regenerating the action potential ate the nodes of ranvier

51
Q

what does the axon look like at the nodes of ranvier?

A

exposed to the external medium

52
Q

what are the five different firing patterns that can be performed by neurons?

A
  1. regular firing
  2. rhythmic bursts
  3. short duration
  4. spontaneous low frequency discharges
  5. steady-slow discharges
53
Q

what is regular firing?

A

trains of action potentials (one spike at a time)

54
Q

what is a feature of regular firing?

A

spike frequency adaptation

55
Q

what is spike frequency adaptation?

A

the tendency to slow down in frequency with time

56
Q

what is an example of regular firing?

A

cortical/hippocampal pyramidal cells

57
Q

what are rhythmic bursts of action potentials?

A

when clusters of APs are generated through activation of Ca2+ currents

58
Q

what is an example of rhythmic bursts of action potentials?

A

thalamic relay neurons (they can perform phasic bursts and slower discharges)

59
Q

what are short duration action potentials?

A

action potentials that have high frequencies (>300 HZ)

60
Q

what is an example of short duration action potentials?

A

fast spiking neurons like GABAergic interneurons

61
Q

what cells display spontaneous low frequency discharges?

A

neuromodulatory neurons

62
Q

what is an example of a neuromodulatory neuron?

A

dopaminergic neurons

63
Q

what cells display steady-slow discharges?

A

medial hebanular neurons

64
Q

what are the 3 main features by which ion currents are characterized by

A

1) the type of ions conducted by channels
2) the voltage and time dependence
3) their sensitivity to second messengers

65
Q

what are the different types of Na currents?

A

1) I Na(t)
2) I Na(p)

66
Q

what are the features of the I Na(t) current?

A

transient and can rapidly activate and deactivate action potentials

67
Q

what are the features of the I Na(p) current?

A

persistent and non-inactivating

68
Q

what does non-inactivating enhance?

A

depolarization and steady-state firing

69
Q

what are the different types of Ca currents?

A

1) I (L)
2) I (T)
3) I (P)

70
Q

what are the features of I (L) currents?

A

high threshold currents, long lasting, and slowly inactivate

71
Q

what can display an I (L) current?

A

dendritic spikes

72
Q

what are the features of an I (T) current?

A

low threshold, transient, and rapidly inactivating

73
Q

what firing pattern displays an I (T) current?

A

rhythmic burst firing

74
Q

what cells perform an I (P) current?

A

purkinje cells (their dendritic spikes)

75
Q

what are the different types of K currents?

A

1) I (K)
2) I (C)
3) I (AHP)
4) I (A)
5) I (H)

76
Q

how is the I (K) current activated?

A

by strong depolarization and repolarization of the action potential

77
Q

how is the I (C) current activated?

A

by increasing calcium levels and acton potential repolarization

78
Q

what part of the action potential displays I (AHP) current?

A

afterhypolarization (because of slow adaptation of action potential discharge)

79
Q

what is the I (A) current?

A

transient inactivating current

80
Q

how does the I (H) current occur?

A

via a depolarizing current activated by hyperpolarization

81
Q

what are the two different patterns of activity that thalamic relay neurons display?

A

rhythmic bursts and tonic firing

82
Q

when does the transition from rhythmic burst (phasic) to tonic firing occur in thalamic cells?

A

during sleep to waking

Cellular Neuroscience (1 decks)

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