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Basics Principles of Anesthesia > Basic Local Anesthetics > Flashcards

Basic Local Anesthetics Flashcards

1
Q

Local anesthetics prevent the _______ and _______ of nerve impulses

A

Generation and conduction

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2
Q

How do local anesthetics prevent generation and conduction of nerve impulses?

A

By blocking Na ion influx

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3
Q

Which voltage -gated channels do local anesthetics work?

A

Na channels

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4
Q

What do local anesthetics prevent the transmission of?

A

advancing wave of depolarization down the length of the nerve

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5
Q

Do LAs alter the resting transmembrane potential?

A

No

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6
Q

Do LAs have a little or large effect on the threshold potential?

A

Little

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7
Q

Which subunits are located on the the voltage gated sodium channels?

A

Alpha subunits
Beta subunits

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8
Q

What are the 3 states of the voltage gated sodium channel?

A

Activated
Inactivated
Resting

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9
Q

What is another name for the activated state of voltage gated sodium channels?

A

Open

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10
Q

Which 2 states do LAs have a higher affinity for?

A

Activated & Inactivated

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11
Q

Do LAs have a higher affinity for resting states over the actived & inactivated?

A

No

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12
Q

Repeated ______ facilitates encounter of LA with the sodium channels that are ______ as opposed to the ______

A

Repeated DEPOLARIZATION facilitates encounter of LA with the sodium channels that are ACTIVATED as opposed to the RESTING

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13
Q

Which nerve state is least sensitive to LAs?

A

Resting

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14
Q

Are LAs more or less sensitive to a resting nerve state than a state of repeated stimulation?

A

Less sensitive

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15
Q

In high or low doses of LAs, does increasing or decreasing the stimulation frequency create an increase or decrease in Na flow?

A

In LOW doses of LAs, INCREASING the stimulation frequency create a DECREASE in Na flow?

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16
Q

What channels contain the LA binding site?

A

Voltage gated sodium channel

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17
Q

Which nerves do LAs work on?

A

peripheral nerves

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18
Q

Are Na channels integral membrane proteins?

A

Yes

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19
Q

Where do Na channels initiate and propagate action potentials?

A

axons
dendrites
muscle tissue

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20
Q

Na channels _____ & _____ membrane potential oscillations

A

Na channels INITIATE & MAINTAIN membrane potential oscillations

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21
Q

Which specialized cells do Na channels work on?

A

Heart and brain cells

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22
Q

Do Na channels shape and filter synaptic inputs?

A

Yes

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23
Q

What is the common structural feature found in Na channels and other gated ion channels?

A

6 Transmembrane helical segments

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24
Q

Are Na channels tetrameres?

A

Yes

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25
Q

How many alpha subunits are on a Na channel?

A

1 larger alpha subunit

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26
Q

How many beta subunits are on a Na channel?

A

1 or 2 smaller beta subunits

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27
Q

Which subunit on a Na channel is larger, alpha or beta?

A

Alpha are larger

28
Q

Blocking of impulses in a nerve fiber requires that a defined length of nerve become ______

A

Blocking of impulses in a nerve fiber requires that a defined length of nerve become INEXCITEABLE

29
Q

As the LA concentration increase, should it be applied to a longer or shorter length of nerve to prevent impulse conduction?

A

As the LA concentration increase, should it be applied to a SHORTER length of nerve to prevent impulse conduction

30
Q

Is there a difference in the way LAs inhibit conduction between myelinated and unmyelinated nerve fibers? Or is it the same?

A

Different

31
Q

How does conduction work in myelinated fibers?

A

impulse jumps from one ranvier node to the next

32
Q

In order to block an impulse in a myelinate nerve fiber, how many Na channels in ranvier nodes need to be inhibited?

A

3 successive ranvier nodes

33
Q

Must the 3 ranvier nodes be successive when blocking?

A

Yes, they should be successive

34
Q

Do unmyelinated fibers conduct more quickly or slowly than myelinated?

A

More slowly

35
Q

Are unmyelinated fibers resistant to LAs? Why?

A

Yes, because they have dispersive Na channels throughout their plasma membranes

36
Q

Are unmyelinated fiber larger or smaller in diameter to myelinated?

A

Smaller

37
Q

When an action potential occurs, do Na channels open?

A

Yes

38
Q

When Na channels open, does Na flow extracellular to intracellular or intracellular to extracellular?

A

extracellular to intracellular

39
Q

Does depolarization occur when Na channels open and there is an influx of Na ions?

A

Yes

40
Q

Do Na channels remain open for long?

A

No, they remain open for a short period of time - milliseconds

41
Q

What is another name for Na channels return to resting conformation?

A

Repolarization

42
Q

What is the term for when ion channels go from conducting to nonconducting forms?

A

gating

43
Q

Gating is assumed to result from movements of _______ in response to changes in potential

A

Gating is assumed to result from movements of DIPOLES in response to changes in potential

44
Q

Do LAs bind irreversibly or reversibly?

A

reversibly

45
Q

Is LA binding concentration dependent?

A

Yes

46
Q

Where is the predominant binding site of LAs - in the cell?

A

near cytoplasmic side of the plamsa membrane

47
Q

Can LA molecules pass through the channel itself to reach the binding site?

A

No

48
Q

What is this - soluble & diffuse rapidly in both hydrophilic & hydrophobic environments?

A

Effective LA

49
Q

What is the chemical structure of LAs?

A

Amino amide & esters

50
Q

Do Amino amide & esthers LAs have a tertiary amine group?

A

yes

51
Q

Are unionized base forms of LAs uncharged or charged?

A

uncharged

52
Q

Are unionized base forms of LAs lipophilic or hydrophilic?

A

lipophillic

53
Q

Do unionized base forms of LAs permeate more rapidly through the phospholipid membrane?

A

Yes

54
Q

Are ionized forms of LAs uncharged or charged?

A

charged

55
Q

Are ionized forms of LAs lipophilic or hydrophilic?

A

hydrophillic

56
Q

Do ionized forms of LAs bind with greater affinity to open Na channels?

A

Yes

57
Q

Between ionized forms and unionized base forms, which has a greater affinity to open Na channels?

A

ionized

58
Q

Between ionized forms and unionized base forms, which permeates more rapidly the phospholipid membrane?

A

unionized

59
Q

Which LA form is the predominantly active species at the binding sites on Na channels? Ionized or unionized?

A

Ionized

60
Q

Is the LA change from ionized to unionized a quick occurance?

A

yea, it happens in a fraction of a second

61
Q

What does the meyer overton theory hypothesize about?

A

mechanism of action of LAs

62
Q

What does the hypothesis of the meyer overton theory suggest?

A

That lipid soluble portion of the LA molecule expand the cell membrane & interferes with rapid Na conductance

63
Q

LAs _____the influx of _____ by altering the ______ of membrane

A

LAs INHIBIT the influx of SODIUM by altering the PERMEABILITY of membrane

64
Q

LAs bind to specific ____ within the ____ channel to _____ the threshold potential

A

LAs bind to specific SITES within the SODIUM channel to INCREASE the threshold potential

65
Q

LAs provide a _____blockade that is ______ when molecules ______ from the ______ site

A

LAs provide a REVERSIBLE blockade that is TERMINATED when molecules DIFFUSE from the NERVE site

Basics Principles of Anesthesia (6 decks)

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