neuromuscular transmission
TRANSCRIPT
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NEUROMUSCULAR TRANSMISSION
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OBJECTIVES
Examine the structure of a neuromuscular junction
Understand the sequence of events at the Neuromuscular – junction following a stimulus
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What you need to know: Anatomy of a skeletal muscle
cell Resting membrane potential Action potential Depolarization
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Overview: Skeletal muscle contraction
Stimulated by a nerve ending
Electrical current / action potential
Rise in intracellular calcium
Muscle contraction* excitation-contraction coupling
Muscle sarcolemma
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Anatomy of a Skeletal Muscle and Nerve Ending ( gross microscopic)
The neuromuscular Junction and the Nerve Stimulus
Steps in Acetylcholine synthesis Degradation
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Steps: 1. Synthesis choline + Acetyl-co-A * Choline Acetyl Transferase
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2. storage
3. release
4. Binding of Ach to receptors•EPP•MEPP
5. Degradation choline + Acetate ion* acetylcholinesterase
6. Recycling of cholineCholine – reabsorbed back to the axonal terminal>300,000 vesicles/axonal terminal1,000 – 50,000 Ach Molecules/Vesicle
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DRUGS AFFECTING N-M JUNCTION TRANSMISSIONDrugs that inhibit choline transport to the nerve axon
Hemicholinium
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Drugs that block release of Ach at the presynaptic membraneBOTULINUM TOXINBLACKWIDOW SPIDER VENOM“OPPOSITE”
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Drugs that stimulate the mucle fiber with Ach-like actionCARBACHOL, METACHOLINE, NICOTINE
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DRUGS THAT BLOCK TRANSMISSION AT THE N-M JUNCTION
Neuromuscular Blocking Agent1.Nondepolarizing : Curare, Pancuronium, Tracium
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2. Depolarizingsuccinylcholine
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DRUGS THAT STIMULATE N-M-J BY INACTIVATING ACETYLCHOLINESTERASE
(anti-chease)
1.Reversible type (temporarily binds)Physostigmine, NeostigmineTx: myasthenia Gravis
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DRUGS THAT STIMULATE N-M-J BY INACTIVATING ACETYLCHOLINESTERASE
(anti-chease)
2. Irreversible typeIsoflurophate (Di- isopropyl flourophosphate)-Aging*chemical activatorsPRALIDOXIME ( PAM)