Exam 3-Local Anesthetics

Question 1

Voltage gated Na Channels open in response to

Answer 1

inside of the cell becoming more positive via depolarization

Question 2

Na channel pore is made of

Answer 2

one subunit protein (alpha)

Question 3

alpha unit protein positive areas

Answer 3

sense the change in the voltage state of the cell and repulsive forces between inside of cell and pore cause channel to open

Question 4

Closed state

Answer 4

no ion flow, cell resting state or negative membrane potential. after repolarization the cell ends here

Question 5

Open state

Answer 5

due to the movement of the four positive charge areas in the pore. only open to Na ions!

Question 6

Inactive state

Answer 6

structurally different than closed, found when cell is at higher depolarization. second gate (inactivation gate) closed.

Question 7

AP begins with

Answer 7

Na or Ca entering cell to cause depolarization

Question 8

Three features of APs

Answer 8

1. threshold depolarization 2. all or none 3. ends with brief resting period, during which cell cannot be triggered for another AP

Question 9

Refractory period

Answer 9

channels will not respond while in the inactive state. cannot move to closed states until the cell has repolarized

Question 10

Endogenous ligands for VG channels

Answer 10

there are none. only exogenous and are usually toxins.

Question 11

Local anesthetics are what type of ligand

Answer 11

antagonist, they do not change the pore

Question 12

Local anesthetics bind where

Answer 12

to the inactivation conformation most tightly. slow the channels return to the closed state. prolongs refractory period

Question 13

Local anesthetics and threshold

Answer 13

increase threshold requiring more stimulus to trigger AP. Think about spare receptors….when there are more receptors available, cell is less responsive to ligand.

Question 14

Local anesthetics and AP speed

Answer 14

AP is slowed, fewer channels are available. ability of pumps to move Na out will pass ability of channels to let Na in, so AP slows to zero

Question 15

Local anesthetics and amplitude of AP

Answer 15

fewer channels respond and let in Na, not enough to reach threshold

Question 16

LA targets

Answer 16

more in nerves that are very active or have high firing rate

Question 17

Cells with higher membrane potential

Answer 17

more likely to have inactive channels and therefore will be more receptors the ligand likes. more sensitive to LA

Question 18

Nerve size

Answer 18

small nerves are more senstive

Question 19

Nerve function lost in this order (onset order)

Answer 19

pain, temp, touch, motor

Question 20

Nerve bundles

Answer 20

admin of LA at bundle, motor neurons will see higher concentration than sensory nerve effects on the inside

Question 21

Toxicity

Answer 21

high concentration of LA will bind nAch receptor cause actions at the NM junx and autonomic ganglia ex: convulsions d/t blocking inhibitory NT

Question 22

Cocaine

Answer 22

original. vasoconstriction. primary use limited to respiratory mucosa

Question 23

Procaine (novacaine)

Answer 23

first synthetic local. low potency, slow onset, short-acting

Question 24

Lidocaine (xylocaine)

Answer 24

rapid onset, stronger effect than procaine, intermediate DOA. used as antiarrythmic

Question 25

Bupivicaine (marcaine)

Answer 25

long duration (slow dissociation), more effect on sensory than motor, popular for labor and post-op

Question 26

Etidocaine (duranest)

Answer 26

fast onset like lidocaine, long DOA like bupivicaine and strong effect on motor neurons

Question 27

Mepivacaine (carbocaine)

Answer 27

poor topically, more toxic in newborns d/t pka

Question 28

Tetracaine (pontocaine)

Answer 28

longer duration, slower metabolism-higher toxicity risk, more for spinal

Question 29

Injectable

Answer 29

lidocaine, bupivacaine, procaine, mepivacaine, tetracaine

Question 30

Topical

Answer 30

dibucaine, dyclonine HCL, pramoxine HCP, benzocaine

Question 31

Opthalmic

Answer 31

proparacaine, tertracaine

Question 32

Infiltration

Answer 32

inject into local tissues at nerve ends (dental). larger area=larger dose. duration lengthened with epi. allows normal muscle function.

Question 33

Field block

Answer 33

block nerves farther away from where you are injecting. inject SQ to block further up nerve chain. larger affected for larger dose

Question 34

Nerve block

Answer 34

plexus. usually highly vascularized at center-so there is continuous removal of LA from the area. increased likelihood of systemic effects. goal to produce anesthesia. DO NOT INJECT INTO NERVE BUNDLE

Question 35

Spinal

Answer 35

more dense drug will affect areas further down from administration site. problems due to sympathetic inhibition

Question 36

Answer 36

A. Closed, nothing happening

B. Na Channels are open

C. Inactive

D. Closed. K channels are closing, K going out and cell becoming slightly more negative.