Neuromuscular blocking drugs Flashcards
(34 cards)
what are motor nerves?
cholinergic
How is acetylcholine synthesized?
acetyl CoA and choline by choline acetyltransferase
How is acetyl choline release from the presynaptic terminal?
- an action potential depolarises the membrane
- opens voltage sensitive calcium channels
- calcium influx leads to vesicle exocytosis
What are the targets for acetylcholine at neuromuscular junctions?
-nicotinic acetylcholine receptors on the end plate
What is depolarisation of the membrane called?
end plate potential
What is a graded potential?
-depends on how much acetylcholine is release and how many receptors are stimulated
What breaks down acetylcholine and where is it found?
- acetylcholinesterase
- attached to the basement membrane in the synaptic cleft
WHat are the 3 main neuromuscular blockers?
- tubocurarine
- atracurium
- suxamethonium
what are the 2 subtypes of nicotinic receptors?
- ganglionic
- muscle
What is the structure of nicotinic acetylcholine receptors?
- 5 subunits
- 2 alpha, each must bind to an acetylcholine molecule to be activated
- 2 molecules of acetylcholine for the receptor to be activated
Where is diazepam used and during which process?
- spasmolytic, facilitates GABA transmission
- at the central process, where an action potential is generated in the spinal cord
What is baclofen?
a GABA receptor agonist
When are diazepam and baclofen useful?
- some forms of cerebral palsy
- following a stroke
Where is local anaesthetic applied?
-conduction of action potentials down a motor neurone , block voltage sensitive Na+ channels
Which drugs interfere with acetylcholine release?
- neurotoxins
- hemicholinium
- Ca2+ entry blockers
What drugs act at the depolarisation of the motor end plate?
- suxamthonium (deplolarising)
- tubocurarine (non-depolarising)
Which drug works in the muscle fibres themselves?
-dantrolene (spasmolytic)
What 2 drugs are non -depolarising competitive nicotinic receptor antagonists?
- tubocurarine
- atracurium
Which drug is a depolarising nicotinic receptor agonist?
-suxamethonium
What do you ALWAYS do when giving these drugs?
assist respiration because of its effects on resp muscles
What is the structure of non-depolarising drugs?
- big and bulky
- restricted movement around the bonds
What is the structure of suxamethonium?
- 2 acetylcholine molecules
- flexible and allows rotation
What is the mechanism of action of suxamethonium?
- causes extended end plate depolarisation
- leads to a depolarisation block of the NMJ
- this is called phase 1 block
-it causes fasciculations, which leads to flaccid paralysis
How is suxamethonium administered?
- intravenous
- duration of paralysis 5 minutes
- metabolised by pseudocholinesterase in the liver and plasma
