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37 Cards in this Set
- Front
- Back
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What type of receptors mediate skeletal muscle contraction in response to ACh?
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Nicotinic Receptors
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What activates nicotinic receptors?
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Nicotine or ACh
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What type of nerves innervate nicotinic receptors?
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Somatic (lack a synapse outside the CNS)
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What does an anticholinesterase do?
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Prolongs ACh actions by preventing the degredation of ACh by acetelcholinesterase
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What are 3 types of anticholinesterases?
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Neostigmine, Pyridostigmine and Edrophonium
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Physically, what do anticholinesterases do?
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potentiates muscle contraction; strengthens the muscle
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What drugs would you use in myasthenia gravis?
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Anticholinesterases (Neostigmine, Pyridostigmine, and Edrophonium)
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What is Myasthenia Gravis?
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AI destruction of nicotinic receptors
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What does Botulinum toxin do?
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Blocks ACh release and prevents both muscle depolarization and contraction
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What is Botulinum toxin useful for?
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treating muscle spasms and cosmetics
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What drug is useful in treating malignant hyperthermia?
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Dantrolene (blocks Ca-induce Ca release)
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What does Dantrolene block?
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Blocks contraction, but not depolarization (AP)
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What do anticholinesterases increase?
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ACh concentrations in the vicinity of the nicotinic receptor (outside somatic nerve)
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What does Neostigmine do?
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Stimulates nicotinic receptors by increasing ACh concentrations
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What does Pyridostigmine do?
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(Mestinon, Regonol) Prolongs ACh action by increasing ACh concentrations. Also used prophylactically to prevent actions of nerve gases
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What is soman?
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a nerve gas. Use pyridostigmine to prevent its effects
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What is known as Tensilon?
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Edrophonium
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What is used to diagnose myasthenia gravis from cholinergic crisis?
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Edrophonium
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What would happen when edrophonium is given to someone in a myasthenic crisis?
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Strength increases
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What would happen when edrophonium is given to someone in a cholinergic crisis?
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Strength decreases (excess ACh)
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What is a cholinergic crisis?
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Nicotinic receptors are desensitized with excessive stimulation (Strength decreases)
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Name 3 Neuromuscular blockers (paralytics)
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d-tubocurarine, mivacurium and succinylcholine
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What are two competitive neuromuscular blockers?
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d-tubocurarine and mivacurium
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What is a depolarizing neuromuscular blocker?
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Succinylcholine
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How do competitive blockers (d-tubocurarine and mivacurium) work?
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Compete for nicotinic receptor sites and block them, thus blocking Na influx, depolarization and contraction
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How does a depolarizing neuromuscular blocker (succinylcholine) work?
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depolarizes end plate of muscle which causes chronic Na influx and depolarization which keeps muscles in refractory period (Overstimmulation of nicotinic receptors)
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What reverses competitive neuromuscular blockers?
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anitcholinesterases (neostigmine, pyridostigmine and edrophonium)
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What is most sensitive to succinylcholine?
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chest and abdomen
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What do anticholinesterases do to a depolarizing blocker (succinylcholine)?
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potentiate it (increase the power of)
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What has the slight ability to reverse a competitive blockade?
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Epi and Norepi
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What causes malignant hyperthermia?
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Halothane and succinylcholine
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What is the treatment for malignant hyperthermia?
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Dantrolene
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How does Dantrolene work?
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Inhibits Ca release from SR by blocking the Ryanodine receptor
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Is succinylcholine short or long acting?
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Short due to butyrylcholinesterase
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What effect does succinylcholine have on the lungs?
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can constrict bronchioles
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What drug should you avoid in burn patients?
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Succinylcholine; burned muscle > the concentration of nicotinic recepotrs resulting in excessive K release in response to stimulation
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What protein does Botulinum toxin A cleave and what does that do?
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SNAP25 which is necessary for ACh exocytosis. Thus, when cleaved ACh cannot act to contract muscles.
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