Muscle relaxants

Question 1

Describe the function of the NMJ

Answer 1

for m. contraction
Ach = NT
nicotinic R are acted on by Ach
AchE breaksdown Ach

Question 2

Compare/contrast depolarizing/nondepolarizing NM blockers

Answer 2

Dep: causes prolong activation of nicAch R–>desensitization over time
1. succinylcholine: not broken down by AchE
Use: intubation–>recovery w/in 10 min
Nondep: competitive antagonist at nicR
2. rocuronium: m. relaxation/paralysis during surgery, along w/ general anesthesia–>paralysis lasts 20-35 min

Question 3

Understand m. spasticity and its tx

Answer 3

Inc. alpha motor neuron activity originating in spinal cord–> inc. reflexes and m. tone–>impairs movement and speech; can be from CNS damage: spinal injury, MS, stroke
Tx: spasmolytics
1. Baclofen: GABAb agonist–>inhibits glutamate
2. Tizanadine: alpha2 agonist–>inhibits glutamate? (can cause hypotension)
-both less sedating than benzodiazepines–>act on GABAa)

Question 4

Understand the role of, NMJ in myasthenia gravis and how anticholinesterases can be useful in diagnosis and tx

Answer 4

• autoantibodies against NAChR block or lead to destruction–>m. weakness that increases with use–>ptosis early sign
  tx: edrophonium: antcholinesterases prevent breakdown of Ach so more Ach can act on the decreased number of receptors.