Neuromuscular junction

Question 1

myasthenia gravis

Answer 1

normal neuron, defective receptors at junction, autoimmune disease, antibodies destroy receptors

Question 2

NMJ blocking agents

Answer 2

paralysis
1. competitive (non-depolarizing) - curare
compete with Ach for binding, flaccid paralysis.
non-NMJ effects: at ganglia, muscarinic blocking, histamine release.
NMJ block reversed by AchE inhibitors (neostigmine).
2. non-competitive (depolarizing) - succinylcholine
agonist, persistent activation causes depolarization, irreversible.
NMJ block not reversed by AchE inhibitors.

Question 3

curare

Answer 3

competetive (non-depolarizing).
no effect on nerve transmission, muscle can still be stimulated.
flaccid paralysis, apnea (respiration loss), can cause histamine release, hypotension.
treat with AchE inhibitors (neostigmine).
slow onset (5min), long lasting (1-2hrs).

Question 4

rocuronium

Answer 4

competetive (non-depolarizing).
fast onset (1-2min), short duration (30min), hypersensitivity.
treat with AchE inhibitors (neostigmine).
metabolized in liver.

Question 5

atracurium

Answer 5

competetive (non-depolarizing)
hydrolysis by AchE, replaced by cisartacurium.
treat with AchE inhibitors (neostigmine).
organ independent, stable degradation.
fast onset (2-4min), short duration (30-40min).

Question 6

succinylcholine

Answer 6

non-competitive (depolarizing).
depolarization (fasciculations) followed by desensitization.
fast onset (<1min), short duration (5-10min), less histamine and less effective than curare, metabolized by pseudocholinesterase.
not reversed by AchE inhibitors (neostigmine makes it worse).

Question 7

NMJ blocking agents uses

Answer 7

muscle relaxation in surgery.
orthopedics - fracture alignment.
facilitate intubations.
facilitate internal exams.
prevent trauma (electroshock).

Question 8

dantrolene

Answer 8

inhibits calcium release from SR, liver toxic, muscle weakness.
treat malignant hyperthermia (DOC).

Question 9

succinylcholine adverse reactions

Answer 9

atypical psuedo-AchE (prolonged apnea). hyperkalemia (2-7 days after burn/trauma). malignant hyperthermia (esp. with halothane).