Basic Local Anesthetics

Question 1

Local anesthetics prevent the _______ and _______ of nerve impulses

Answer 1

Generation and conduction

Question 2

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

Answer 2

By blocking Na ion influx

Question 3

Which voltage -gated channels do local anesthetics work?

Answer 3

Na channels

Question 4

What do local anesthetics prevent the transmission of?

Answer 4

advancing wave of depolarization down the length of the nerve

Question 5

Do LAs alter the resting transmembrane potential?

Answer 5

No

Question 6

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

Answer 6

Little

Question 7

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

Answer 7

Alpha subunits
Beta subunits

Question 8

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

Answer 8

Activated
Inactivated
Resting

Question 9

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

Answer 9

Open

Question 10

Which 2 states do LAs have a higher affinity for?

Answer 10

Activated & Inactivated

Question 11

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

Answer 11

No

Question 12

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

Answer 12

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

Question 13

Which nerve state is least sensitive to LAs?

Answer 13

Resting

Question 14

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

Answer 14

Less sensitive

Question 15

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

Answer 15

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

Question 16

What channels contain the LA binding site?

Answer 16

Voltage gated sodium channel

Question 17

Which nerves do LAs work on?

Answer 17

peripheral nerves

Question 18

Are Na channels integral membrane proteins?

Answer 18

Yes

Question 19

Where do Na channels initiate and propagate action potentials?

Answer 19

axons
dendrites
muscle tissue

Question 20

Na channels _____ & _____ membrane potential oscillations

Answer 20

Na channels INITIATE & MAINTAIN membrane potential oscillations

Question 21

Which specialized cells do Na channels work on?

Answer 21

Heart and brain cells

Question 22

Do Na channels shape and filter synaptic inputs?

Answer 22

Yes

Question 23

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

Answer 23

6 Transmembrane helical segments

Question 24

Are Na channels tetrameres?

Answer 24

Yes

Question 25

How many alpha subunits are on a Na channel?

Answer 25

1 larger alpha subunit

Question 26

How many beta subunits are on a Na channel?

Answer 26

1 or 2 smaller beta subunits

Question 27

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

Answer 27

Alpha are larger

Question 28

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

Answer 28

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

Question 29

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

Answer 29

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

Question 30

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

Answer 30

Different

Question 31

How does conduction work in myelinated fibers?

Answer 31

impulse jumps from one ranvier node to the next

Question 32

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

Answer 32

3 successive ranvier nodes

Question 33

Must the 3 ranvier nodes be successive when blocking?

Answer 33

Yes, they should be successive

Question 34

Do unmyelinated fibers conduct more quickly or slowly than myelinated?

Answer 34

More slowly

Question 35

Are unmyelinated fibers resistant to LAs? Why?

Answer 35

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

Question 36

Are unmyelinated fiber larger or smaller in diameter to myelinated?

Answer 36

Smaller

Question 37

When an action potential occurs, do Na channels open?

Answer 37

Yes

Question 38

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

Answer 38

extracellular to intracellular

Question 39

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

Answer 39

Yes

Question 40

Do Na channels remain open for long?

Answer 40

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

Question 41

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

Answer 41

Repolarization

Question 42

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

Answer 42

gating

Question 43

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

Answer 43

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

Question 44

Do LAs bind irreversibly or reversibly?

Answer 44

reversibly

Question 45

Is LA binding concentration dependent?

Answer 45

Yes

Question 46

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

Answer 46

near cytoplasmic side of the plamsa membrane

Question 47

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

Answer 47

No

Question 48

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

Answer 48

Effective LA

Question 49

What is the chemical structure of LAs?

Answer 49

Amino amide & esters

Question 50

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

Answer 50

yes

Question 51

Are unionized base forms of LAs uncharged or charged?

Answer 51

uncharged

Question 52

Are unionized base forms of LAs lipophilic or hydrophilic?

Answer 52

lipophillic

Question 53

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

Answer 53

Yes

Question 54

Are ionized forms of LAs uncharged or charged?

Answer 54

charged

Question 55

Are ionized forms of LAs lipophilic or hydrophilic?

Answer 55

hydrophillic

Question 56

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

Answer 56

Yes

Question 57

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

Answer 57

ionized

Question 58

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

Answer 58

unionized

Question 59

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

Answer 59

Ionized

Question 60

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

Answer 60

yea, it happens in a fraction of a second

Question 61

What does the meyer overton theory hypothesize about?

Answer 61

mechanism of action of LAs

Question 62

What does the hypothesis of the meyer overton theory suggest?

Answer 62

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

Question 63

LAs _____the influx of _____ by altering the ______ of membrane

Answer 63

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

Question 64

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

Answer 64

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

Question 65

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

Answer 65

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