Neuromuscular Blocking Agents

Question 1

Motor nerves release ____ onto ____ receptors

Answer 1

neuromuscular nicotinic receptors mediate skeletal muscle contraction in response to acetylcholine

Question 2

Somatic Nerves emanate from the ______ and innervate ______ with ___ synapses outside the CNS

Answer 2

Somatic Nerves emanate from the spinal cord and innervate skeletal muscle with no synapses outside the CNS

Question 3

Somatic nerve signal terminated by:

Answer 3

Signal is terminated by degradation of Acetylcholine - by Acetylcholinesterases

Question 4

Anticholinesterases are useful in treating ____________

Answer 4

Anticholinesterases are useful in treating Myasthenia gravis

Question 5

___________ are useful in treating Myasthenia gravis

Answer 5

Anticholinesterases are useful in treating Myasthenia gravis

Question 6

Acetylcholine + Acetylcholinesterase –>

Answer 6

Acetate + Choline

Question 7

Acetylcholine at nicotinic receptor results in …. (pathway)

Answer 7

Na influx
Depolarization
muscle action potential
opening of voltage-sensitive Ca2+ channel
release of Ca2+ from sarcoplasmic reticulum
contraction

Question 8

Nicotinic receptor historically blocked by

Answer 8

historically blocked by alpha-bungarotoxin from krait or cobra (Naja naja) venom (snake)

Question 9

Agents prolonging Acetylcholine action (____, _____, _____) _______ muscle depolarization & contraction

Answer 9

Agents prolonging Acetylcholine action (Neostigmine, Pyridostigmine, Edrophonium) augment muscle depolarization & contraction- relevant to Myasthenia gravis

Question 10

Agents blocking acetycholine release (_______) will prevent both _____ & _______

Answer 10

Agents blocking acetycholine release (Botulinum toxin) will prevent both muscle depolarization & contraction- relevant to cosmetics, muscle spasms

Question 11

nicotinic receptor blockers (_____, ________) will prevent both ___________ & _________

Answer 11

nicotinic receptor blockers (d-tubocurarine, Mivacurium) will prevent both muscle depolarization & contraction- relevant to surgical paralysis

Question 12

Something that blocks calcium-induced calcium release (________) will block ________ but not _______

Answer 12

Something that blocks calcium-induced calcium release (Dantrolene) will block contraction but not depolarization- relevant to Malignant Hyperthermia

Question 13

Autoimmune disease resulting in destruction of nicotinic receptors on skeletal muscle

Answer 13

Myasthenia gravis

Question 14

Treatment for myasthenia gravis

Answer 14

Treatment includes anticholinesterases (pyridostigmine, neostigmine)

Question 15

Diagnosis for myasthenia gravis

Answer 15

Diagnosis can include the short acting anticholinesterase edrophonium (Tensilon test)

Question 16

(Mestinon, Regonol) - used in myasthenia gravis or to reverse competitive neuromuscular antagonism; can be used prophylactically to prevent actions of nerve gases (tabun, soman)

Answer 16

Pyridostigmine

Question 17

(Prostigmin)- used in myasthenia gravis but poorly absorbed from the gut; used more in hospitalized patients

Answer 17

Neostigmine

Question 18

used to diagnose myasthenia gravis (vs. cholinergic crisis)

Answer 18

Edrophonium (Tensilon injectable)

increases strength in a myasthenic crisis and decreases strength in a cholinergic crisis (too much acetylcholine)

Question 19

principal behind a cholinergic crisis

Answer 19

nicotinic receptor - excessive stimulation of nicotinic receptors desensitizes organ to further stimulation

Question 20

Toxicity of anticholinesterases

Answer 20

SLUDGE (sweating, lacrimation, urination, diarrhea, GI distress, emesis)

Question 21

Used primarily in surgery to paralyze skeletal muscle

Answer 21

Neuromuscular blockers

Question 22

What do neuromuscular blockers block?

Answer 22

block nicotinic receptors on skeletal muscle

Question 23

Two types neuromuscular blockers?

Answer 23

Competitive, depolarizing

Question 24

Competitive blockers (eg)

Answer 24

d-tubocurarine, pancuronium, vecuronium, atracurium, metocurine, pipecuronium, mivacurium, rocuronium

Question 25

Depolarizing agents (Eg)

Answer 25

succinylcholine

Question 26

Mechanism of competitive blockers

Answer 26

competitive compete for nicotinic receptor sites - block Na+ influx, depolarization and contraction

Question 27

Succinylcholine mechanism

Answer 27

depolarizes end plate of muscle- chronic Na+ influx causes depolarization; fasciculations precede flaccid paralysis

Question 28

Anticholinesterases reverse block of ______

Answer 28

Competitive blockers

Question 29

Anticholinesterases may augment block of _________

Answer 29

Depolarizing blockers

Question 30

Fasciculations precede flaccid paralysis by ________

Answer 30

Depolarizing blockers

Question 31

___________ agents release K

Answer 31

Depolarizing agents

Question 32

Ether, halogenated anesthetics, streptomycin, tetracycline ________ competitive block

Answer 32

Ether, halogenated anesthetics, streptomycin, tetracycline enhance competitive block

Question 33

Anticholinesterases- _________ competitive blocker but __________ a depolarizing blocker

Answer 33

Anticholinesterases- antagonize competitive blocker but potentiate a depolarizing blocker

Question 34

epinephrine and norepinephrine - slight ability to reverse _____________

Answer 34

epinephrine and norepinephrine - slight ability to reverse competitive blockade

Question 35

Toxic effects of neuromuscular blockers

Answer 35

Apnea, histamine release, cardiovascular collapse | Malignant hyperthermia caused by halothane and succinylcholine

Question 36

Tx for malignant hyperthermia

Answer 36

treatment is dantrolene (dantrium) - inhibits Ca2+ release from sarcoplasmic reticulum by blocking the Ryanodine receptor (Calcium-induced calcium release)

Question 37

Uses for neuromuscular blockers

Answer 37

with anesthetics; prevention of seizures in electroshock therapy; nerve root pain vs muscle spasm impinging on nerve

Question 38

Absorption, metabolism of neuromuscular blockers

Answer 38

Absorption- Quaternary ammonium (i.v.); Metabolism - usually by kidneys except atracurium

Question 39

Depolarizing agents - avoid use in ____ patients, why

Answer 39

Avoid in burn patients (burned muscle increases the concentration of nicotinic receptors resulting in excessive potassium release in response to succinylcholine)

Question 40

Usually used for tracheal intubation to prevent aspiration of gastric contents; __________ is preferred for this because of its rapid action

Answer 40

succinylcholine

Question 41

Can produce malignant hyperthermia -treat with calcium antagonist, dantrolene

Answer 41

succinylcholine

Question 42

Succinylcholine has ______ duration of action

Answer 42

Short duration of action because of rapid metabolism (butyrylcholinesterase)

Question 43

Botulinum toxin mechanism

Answer 43

Prevents acetylcholine release by cleaving proteins (SNAP25) necessary for acetylcholine exocytosis