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Physiology > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Speed of depolarization:

A

about 1ms 1/1000th of a sec

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2
Q

Speed of AP:

A

about 200 mph

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3
Q

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

A

2 Na (depolarize) and K (repolarize)

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4
Q

What causes the termination of the AP?

A

Opening of the K channels

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5
Q

T or F? APs are analog signals.

A

F. digital. Its there or it’s not

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6
Q

This type of signal can very over an enormous range:

A

graded analog

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7
Q

What produces the absolute and relative refractory periods?

A

recovery oft he Na and K channels

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8
Q

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

A

T. Just requires a stronger stimulus

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9
Q

What type of potentials are produces at the synapse?

A

graded

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10
Q

T or F? Graded potentials can summate.

A

T

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11
Q

T or F? APs can summate.

A

F

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12
Q

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

A

trigger zone (initial segment)

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13
Q

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

A

graded

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14
Q

This type of potential can be used to compute things

A

graded

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15
Q

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

A

F. They do diminish with distance

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16
Q

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

A

they produce spikes

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17
Q

Does a graded potential start below or above threshold?

A

Above

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18
Q

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

A

It depends on the initial strength of the stimulus.

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19
Q

Will the release of Glu depolarize or depolarize a cell?

A

depolarize

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20
Q

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

A

F. localized in the trigger zone

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21
Q

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

A

Na leaks out and the inside will be less positive

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22
Q

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

A

T

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23
Q

Are APs generated along efferent or afferent neurons?

A

Afferent

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24
Q

What is AP frequency proportional to?

A

Graded potential amplitude

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25
Q

What happens if the graded potential is just at threshold?

A

it will on ly produce a few APs

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26
Q

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

A

Yes, if they are large enough

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27
Q

The strength of a stimulus is encoded in:

A

the graded potential

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28
Q

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

A

T

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29
Q

A strong, graded potential will produce:

A

many APs at a high frequency

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30
Q

How can the frequency of APs be increased?

A

increase the strength of the graded potential

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31
Q

The size of the graded potential is proportional to:

A

the number of activated channels

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32
Q

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

A

T. EPSP or IPSP

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33
Q

T or F? Naps have variable amplitude

A

F. Graded potentials do

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34
Q

Are graded potentials at the synapse fast or slow?

A

slow

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35
Q

Are APs at axon initial segment slow or fast?

A

fast

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36
Q

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

A

F. APs do

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37
Q

The polarity of this type of potential can vary:

A

graded potential

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38
Q

What encodes the strength of the stimulus in neurons?

A

spike frequency and EPSP amplitude of the synaptic current

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39
Q

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

A

amplitude and spike frequency

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40
Q

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

A

F. More negative

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41
Q

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

A

input signal

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42
Q

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

A

conduction signal

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43
Q

Where does a GP typically occur in a neuron?

A

dendrites and cell bodies

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44
Q

Where does an AP typically occur in a neuron?

A

trigger zone through an axon

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45
Q

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

A

mechanically, chemically, or voltage-gated channels

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46
Q

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

A

Voltage-gated only

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47
Q

What ions are involved with GPs?

A

usually Na, Cl, and Ca

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48
Q

What ions are involved with APs?

A

Na and K

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49
Q

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

A

either

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50
Q

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

A

depolarizing

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51
Q

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

A

initial stimulus, can be summed

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52
Q

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

A

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

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53
Q

What initiates the signal for a GP?

A

entry of ions through channels

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54
Q

What initiates the signal for a AP?

A

Above-threshold GP at the trigger zone

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55
Q

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

A

F.

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56
Q

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

A

frequency of a series of APs

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57
Q

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

A

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

58
Q

3 types of channels leading to an AP:

A
  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
Q

What type of channel produces the resting membrane potential?

A

Unregulated, leak channels

60
Q

What type of channel produces the graded potential?

A

Synaptic, ligand-gated channels

61
Q

What type of channel produces the AP?

A

Voltage gated channel

62
Q

What channels cause the undershoot?

A

K channels

63
Q

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

A

Rising phase, Decay

64
Q

To what mV does a typical undershoot reach?

A

-90 mV

65
Q

To what mV does an AP rise?

A

+60 mV

66
Q

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

A

F. Vice versa

67
Q

Why do K channels create an undershoot?

A

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

68
Q

Threshold is the voltage at which the sodium current becomes:

A

regenerative

69
Q

What becomes regenerative at the threshold?

A

the Na current

70
Q

What activates K channels?

A

depolarization

71
Q

What does it mean that the AP is regenerative?

A

Na channels activate more Na channels

72
Q

When does the Na current become regenerative?

A

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

73
Q

What type of cycle controls the Na channels?

A

feedback cycle

74
Q

What closes the Na channel at the RMP?

A

activation gate

75
Q

What stops Na from flowing through the Na channel?

A

the inactivation gate

76
Q

Where is the inactivation gate located?

A

intracellular side of the Na channel

77
Q

Where is the activation gate located?

A

In the intramembraneous portion of the Na channel

78
Q

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

A

S4 segment

79
Q

What does the S4 segment respond to?

A

change in voltage

80
Q

How long does the Na channel typically remain open?

A

a couple ms’s

81
Q

How many “doors” does the Na channel have?

A

2, both must be open for Na to enter cell

82
Q

This is the only way for the cell to recover:

A

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

83
Q

What is the benefit of the inactivation gate?

A

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

84
Q

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

A

F. Activation gate is closed, inactivation gate is open

85
Q

Is there a fast or slow recovery from inactivation?

A

slow

86
Q

What is happening during the slow recovery from inactivation?

A

repolarization

87
Q

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

A

No, the activation gate is open

88
Q

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

A

T

89
Q

When a channel is blocked which gate gets clogged?

A

Activation gate

90
Q

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

A

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

91
Q

Voltage sensor:

A

S4

92
Q

S4:

A

Voltage sensor

93
Q

S5-6:

A

Activation gate

94
Q

Activation gate:

A

S5-6

95
Q

Channel pore:

A

P-loop

96
Q

P-loop:

A

channel pore

97
Q

What is the inactivation gate a part of?

A

the channel protein

98
Q

How many domains does the voltage gated Na channel have?

A

4 (each with 6 transmembrane segments)

99
Q

In which domain i the P-loop found?

A

Domain IV

100
Q

How can the refractory period be tested?

A

by varying time bw 2 stimuli

101
Q

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

A

F. increases

102
Q

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

A

F. K are still open, Na are closed

103
Q

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

A

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

104
Q

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

A

increase

105
Q

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

A

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

106
Q

What prevents back propagation of the AP?

A

ARP

107
Q

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

A

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

108
Q

What repolarizes the membrane?

A

loss of L from the cytoplasm

109
Q

What determines spike frequency?

A

relative refractory period

110
Q

Excitability is linked to:

A

proportion of Na+ channels that can activate and not inactivated

111
Q

What affects the spike threshold?

A

the rate of graded depolarization

112
Q

What is the goal of the graded potential?

A

to allow enough positive charge to create a regenerative event

113
Q

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

A

rapidly

114
Q

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

A

F. vice versa, slowly developing, quickly

115
Q

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

A

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

116
Q

Extracellular levels of __ are increased in hyperkalemia.

A

K

117
Q

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

A

extra

118
Q

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

A

less negative (more positive)

119
Q

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

A

closer to

120
Q

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

A

more likely

121
Q

T or F? Hyperkalemia hyperpolarizes the cell membrane.

A

F. Hypokalemia hyper polarizes the cell membrane

122
Q

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

A

less

123
Q

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

A

further

124
Q

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

A

more positive

125
Q

Which makes the cell hyperexcitable, hyper or hypokalemia?

A

hyperkalemia

126
Q

Intra and extracellular concentrations of K for a normal cell:

A

150 mM in, 5 mM out

127
Q

2 drugs that can block voltage-gated Na channels:

A

tetrodoxin (TTX) and local anesthetics

128
Q

How do local anesthetics block AP from forming?

A

block active Na and K channels or enhance Na channel inactivation

129
Q

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

A

small

130
Q

What does TTX stand for?

A

tetrodoxin

131
Q

Lidocaine prevents recovery from:

A

the inactivated state and prevents the formation of APs

132
Q

Describe pain conveying fibers:

A

small diameter, non- or lightly-myelinated

133
Q

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

A

9

134
Q

These subunits make of Na channels in the CNS:

A

Nav1.1, 1.2, 1.3, 1.6

135
Q

These subunits make of Na channels in the PNS:

A

Nav1.1, 1.6, 1.7, 1.8, 1.9

136
Q

These subunits make of Na channels in the skeletal muscle:

A

Nav1.4

137
Q

These subunits make of Na channels in the cardiac muscle:

A

Nav1.5

138
Q

How many genes express the subunits of the Na channels?

A

9

139
Q

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

A

Nav1.7 PNS

140
Q

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

A

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

Physiology (55 decks)

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