anatomy and physiology of neuromuscular junction
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ANATOMY AND PHYSIOLOGY OF NEUROMUSCULAR JUNCTION
PRESENTOR : Dr Goutham
MODERATOR : Dr Vijesh
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NEUROMUSCULAR JUNCTION
Synapse b/w motor nerve and muscleEach motor neuron runs from ventral
horn of spinal cordGap b/w nerve and muscle is the
synaptic cleft which is 20 nm wide
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MUSCLE END
Corrugated with invaginations to form primary and secondary cleft along muscle
Shoulders contain Ach receptors which are densely packed
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PERIJUNCTIONAL ZONE
Area beyond the junctional areaCritical to NMJ transmission Has high density of sodium channelsResponds to depolarisation produced by
Ach receptors and initiates contraction
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Vesicles containing transmitters are seen clustering alongside the nerve terminal – ACTIVE ZONES / RELEASE SITE
Voltage gated calcium channels present in b/w vesicles through which calcium enters and cause release of transmitter
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FORMATION OF ACETYLCHOLINE
How ? Axoplasm
CHOLINE + ACETYL CoA
( CAT ) ECF mitochondria
diet hydrolyzed acetylcholine liver
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TRANSMISSION
MEPP : produced by quanta/packagesAt rest potential difference is -90 mVDuring AP > Na+ influx >depolarization >
opens Ca channels > release of Ach from vesicles
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CALCIUM CHANNELS -TYPES
P type L type 1.voltage dependant non dependant
2.not affected by Ca channel blockers affected
3.release of transmitter
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SYNAPTIC VESICLE
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SYNAPTIC VESICLE
VESICLE PROTIENSSynaptophysin SynaptotagminSynaptobrevin
CLINICAL ASPECT : Botulinum toxin/tetanus toxin
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EXOCYTOSIS
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REMOVAL OF Ach
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RECEPTORS
Ach RECEPTOR
1. Post junctional,junctional and extra junctional
2. Pre junctional .
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CONTD…..
Has 5 subunits. Alpha(2),beta,delta,e
psilon. Both alpha units
occupied by agonist.
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MECHANISM OF ION FLOW
Receptor undergo conformational change
Opens channel
Allows cation movement
AP created
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MUSCLE CONTRACTION
Myofibrils consists of sacromeres.
Each sacromere –actin and myosin.
Tropomyosin and troponin attached to actin
AP transverse tubules,sarcoplasmic reticulum releases ca++.
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EXTRA JUNCTIONAL RECPTORS
Denervation of the muscle. Seen in
1. Fetus
2. Pts with stroke
3. Spinal cord injuries
4. Burns
5. bedridden
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