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Flashcards in Lecture 3 Deck (140):
1

Speed of depolarization:

about 1ms 1/1000th of a sec

2

Speed of AP:

about 200 mph

3

How many voltage gated channels are involved in the formation of APs?

2 Na (depolarize) and K (repolarize)

4

What causes the termination of the AP?

Opening of the K channels

5

T or F? APs are analog signals.

F. digital. Its there or it's not

6

This type of signal can very over an enormous range:

graded analog

7

What produces the absolute and relative refractory periods?

recovery oft he Na and K channels

8

T or F? It is possible to produce another AP during the relative refractory period.

T. Just requires a stronger stimulus

9

What type of potentials are produces at the synapse?

graded

10

T or F? Graded potentials can summate.

T

11

T or F? APs can summate.

F

12

This segment of the neuron has a very high concentration of sodium channels

trigger zone (initial segment)

13

This type of potential is good at starting to produce a response that you can finely tune:

graded

14

This type of potential can be used to compute things

graded

15

T or F. Graded potentials (GP's) do not diminish with distance.

F. They do diminish with distance

16

What happens in GPs are above the threshold in the Trigger Zone?

they produce spikes

17

Does a graded potential start below or above threshold?

Above

18

Is a GP above or below the threshold at the trigger zone?

It depends on the initial strength of the stimulus.

19

Will the release of Glu depolarize or depolarize a cell?

depolarize

20

T or F? Na channels can be found all over the neuron.

F. localized in the trigger zone

21

Why is there less positive charge as you get closer to the trigger zone with a graded potential?

Na leaks out and the inside will be less positive

22

T or F? A weak stimulus will release little neurotransmitter and a strong stimulus will release more.

T

23

Are APs generated along efferent or afferent neurons?

Afferent

24

What is AP frequency proportional to?

Graded potential amplitude

25

What happens if the graded potential is just at threshold?

it will on ly produce a few APs

26

Can EPSPs (Excitatory post-synatic potential) produce APs?

Yes, if they are large enough

27

The strength of a stimulus is encoded in:

the graded potential

28

T or F? The bigger the graded potential, the higher the frequency.

T

29

A strong, graded potential will produce:

many APs at a high frequency

30

How can the frequency of APs be increased?

increase the strength of the graded potential

31

The size of the graded potential is proportional to:

the number of activated channels

32

T or F? Graded potentials can be both positive and negative

T. EPSP or IPSP

33

T or F? Naps have variable amplitude

F. Graded potentials do

34

Are graded potentials at the synapse fast or slow?

slow

35

Are APs at axon initial segment slow or fast?

fast

36

T or F? Graded potentials at synapse have a stereotyped response.

F. APs do

37

The polarity of this type of potential can vary:

graded potential

38

What encodes the strength of the stimulus in neurons?

spike frequency and EPSP amplitude of the synaptic current

39

Both of these will be lower with a mall graded potential in comparison to a large graded potential:

amplitude and spike frequency

40

T or F? The inside of the cell becomes more positive with an IPSP.

F. More negative

41

What type of signal does a graded potential get in a neuron?

input signal

42

What type of signal does a AP get in a neuron?

conduction signal

43

Where does a GP typically occur in a neuron?

dendrites and cell bodies

44

Where does an AP typically occur in a neuron?

trigger zone through an axon

45

What type(s) of gated ion channel are involved with graded potentials?

mechanically, chemically, or voltage-gated channels

46

What type(s) of gated ion channel are involved with APs?

Voltage-gated only

47

What ions are involved with GPs?

usually Na, Cl, and Ca

48

What ions are involved with APs?

Na and K

49

Does a graded potential (lead to?) a signal that is depolarizing or hyperpolarizing?

either

50

Does an AP (lead to?) a signal that is depolarizing or hyperpolarizing?

depolarizing

51

What does the strength of the signal of the GP depend upon?

initial stimulus, can be summed

52

What does the strength of the signal of the AP depend upon?

it is always the same (all-or-none), cannot be summed

53

What initiates the signal for a GP?

entry of ions through channels

54

What initiates the signal for a AP?

Above-threshold GP at the trigger zone

55

T or F? There is a minimum level required to initiate a GP/

F.

56

What is the initial stimulus strength indicated by for a GP?

frequency of a series of APs

57

T or F? All cell at rest will have no open channels.

F. some are open (leak channels), we don't know which

58

3 types of channels leading to an AP:

1. Unregulated (leak) channels produce the resting membrane potential
2. Synaptic, ligand-gated channels produce graded potential
3. Voltage gated channels produce the AP

59

What type of channel produces the resting membrane potential?

Unregulated, leak channels

60

What type of channel produces the graded potential?

Synaptic, ligand-gated channels

61

What type of channel produces the AP?

Voltage gated channel

62

What channels cause the undershoot?

K channels

63

What are the names of the two sides of the spike of an AP called?

Rising phase, Decay

64

To what mV does a typical undershoot reach?

-90 mV

65

To what mV does an AP rise?

+60 mV

66

T or F? K channels have an automated shut off mechanism whereas Na channels do not.

F. Vice versa

67

Why do K channels create an undershoot?

They linger open and don't have a shut off mechanism

68

Threshold is the voltage at which the sodium current becomes:

regenerative

69

What becomes regenerative at the threshold?

the Na current

70

What activates K channels?

depolarization

71

What does it mean that the AP is regenerative?

Na channels activate more Na channels

72

When does the Na current become regenerative?

when it exceeds the K current (is this always the same mV as the threshold?)/ overcome other voltages that might be working

73

What type of cycle controls the Na channels?

feedback cycle

74

What closes the Na channel at the RMP?

activation gate

75

What stops Na from flowing through the Na channel?

the inactivation gate

76

Where is the inactivation gate located?

intracellular side of the Na channel

77

Where is the activation gate located?

In the intramembraneous portion of the Na channel

78

Response of this segment allows for Na to rush in through the Na channels:

S4 segment

79

What does the S4 segment respond to?

change in voltage

80

How long does the Na channel typically remain open?

a couple ms's

81

How many "doors" does the Na channel have?

2, both must be open for Na to enter cell

82

This is the only way for the cell to recover:

to hyperpolarize, otherwise the channel is essentially useless bc that 2nd of the 2 gates is closed

83

What is the benefit of the inactivation gate?

helps to create rapid hyperpolarizaton (Na channels aren't fighting it)

84

T or F? Both the activation gate and the inactivation gate are closed in the resting state.

F. Activation gate is closed, inactivation gate is open

85

Is there a fast or slow recovery from inactivation?

slow

86

What is happening during the slow recovery from inactivation?

repolarization

87

Are both the activation gate and the inactivation gate closed during inactivation?

No, the activation gate is open

88

T or F? The inactivation gate can be closed even when depolarized.

T

89

When a channel is blocked which gate gets clogged?

Activation gate

90

T or F? Na and K channels both have activation gates and inactivation gates.

F. Na channels do, K channels only have activation gates

91

Voltage sensor:

S4

92

S4:

Voltage sensor

93

S5-6:

Activation gate

94

Activation gate:

S5-6

95

Channel pore:

P-loop

96

P-loop:

channel pore

97

What is the inactivation gate a part of?

the channel protein

98

How many domains does the voltage gated Na channel have?

4 (each with 6 transmembrane segments)

99

In which domain i the P-loop found?

Domain IV

100

How can the refractory period be tested?

by varying time bw 2 stimuli

101

T or F? Spike amplitude decreases with time during the relative refractory period.

F. increases

102

T or F? Both Na and K channels are close at the end of the absolute refractory period.

F. K are still open, Na are closed

103

T or F? The excitability of a neuron increase during the absolute refractory period.

F. remains at zero until the start of the relative refractory period

104

Does a decrease or increase in the K conductance cause hyperpolarization of the cell?

increase

105

T or F? As soon as all the Na channels have recovered fully another AP can easily be produced.

F. You would now have to depolarize more to produce a 2nd AP because the cell is hyperpolarized

106

What prevents back propagation of the AP?

ARP

107

In order for AP to propagate w/in a cell (+/-) charges flow into the adjacent sections of the axon by local current flow.

+, there is always a - charge on the opposite side of the PM

108

What repolarizes the membrane?

loss of L from the cytoplasm

109

What determines spike frequency?

relative refractory period

110

Excitability is linked to:

proportion of Na+ channels that can activate and not inactivated

111

What affects the spike threshold?

the rate of graded depolarization

112

What is the goal of the graded potential?

to allow enough positive charge to create a regenerative event

113

Are GP's more likely to produce an AP when they occur slowly, rapidly, or it doesn't make a difference.

rapidly

114

T or F? A quickly developing graded potential will have a higher AP threshold than a slow GP.

F. vice versa, slowly developing, quickly

115

T or F? A large GP will always produce an AP

F. If it is large and SLOW it will not bc many Na channels have inactivated during depolarization

116

Extracellular levels of __ are increased in hyperkalemia.

K

117

Is hyperkalemia related to intracellular K levels or extracellular K levels?

extra

118

Will the inside a the cell of a person who is hyperkalemic be more or less negative?

less negative (more positive)

119

Does hyperkalemia bring the membrane closer to or further from threshold?

closer to

120

Does hyperkalemia lead to a more likely or less likely AP?

more likely

121

T or F? Hyperkalemia hyperpolarizes the cell membrane.

F. Hypokalemia hyper polarizes the cell membrane

122

Does hypokalemia make the neuron more or less likely to fire an AP?

less

123

Does hypokalemia bring the membrane closer to or further from threshold?

further

124

Will the inside of a cell become more or less positive if the extracellular concentration of K raises?

more positive

125

Which makes the cell hyperexcitable, hyper or hypokalemia?

hyperkalemia

126

Intra and extracellular concentrations of K for a normal cell:

150 mM in, 5 mM out

127

2 drugs that can block voltage-gated Na channels:

tetrodoxin (TTX) and local anesthetics

128

How do local anesthetics block AP from forming?

block active Na and K channels or enhance Na channel inactivation

129

Do local anesthetics work better on small or large diameter fibers?

small

130

What does TTX stand for?

tetrodoxin

131

Lidocaine prevents recovery from:

the inactivated state and prevents the formation of APs

132

Describe pain conveying fibers:

small diameter, non- or lightly-myelinated

133

How many different subunits can voltage-gated Na channels be made of?

9

134

These subunits make of Na channels in the CNS:

Nav1.1, 1.2, 1.3, 1.6

135

These subunits make of Na channels in the PNS:

Nav1.1, 1.6, 1.7, 1.8, 1.9

136

These subunits make of Na channels in the skeletal muscle:

Nav1.4

137

These subunits make of Na channels in the cardiac muscle:

Nav1.5

138

How many genes express the subunits of the Na channels?

9

139

Pts with a mutation of this subunit of the Na channels can not sense pain:

Nav1.7 PNS

140

3 types of disorders resulting from mutation in Nav1.7:

Congenital insensitivity to pain (CIP), inherited erythromelalgia (IEM), paroxysmal extreme pain disorder (PEPD)