Neuromuscular junction

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NEUROMUSCULAR JUNCTION Presented by: VARNAKA C H 1 ST BNYS

Transcript of Neuromuscular junction

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NEUROMUSCU

LAR JUNCTION

Presented by:VARNAKA C H 1ST BNYS

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INDEX

• Definition• Structure• Neuromuscular transmission• Neuromuscular blockers• Neuromuscular stimulators• Motor unit• Applied physiology• Questions from previous exams

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• Definition Junction between terminal branch of nerve fiber and muscle fiber

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Structure

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• Axon terminal- terminal branch of nerve fiber• Motor end plate- bulb like expansion of axon

terminal• Synaptic trough/ gutter- depression on the

muscle fiber due to invagination of motor end plate

• Subneural cleft- numerous folds of post synaptic membrane

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• Presynaptic membrane- membrane of nerve ending

• Postsynaptic membrane- membrane of muscle fiver

• Synaptic cleft- space between post and presynaptic membrane

• Basal lamina- thin spongy layer of reticular matrix in synaptic cleft

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Neuromuscular transmission

• Transfer of information from motor nerve ending to the muscle fiber through neuromuscular junction to initiate muscle contraction

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Series of events

1. Release of acetly choline2. Action of acetly choline3. Development of end plate potential4. Development of miniature end plate

potential5. Destruction of acetyl choline

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Release of acetly choline

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Action of acetly choline

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Development of end plate potential

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Devolpment of miniature end plate potential

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Destruction of acetyl choline

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Neuromuscular blockers

Drugs which prevent transmission of impulse across neuromuscular junction

significance..? useful in surgical and

trauma care

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• Curare - blocks ach receptors by binding• Bungarotoxin - (snake venom extract) blocks ach receptors• Botulinum toxin - (clostridium botulinum) prevents realease of ach from axon terminal

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Neuromuscular stimulators

Inactivate Ach esterase

Repeated stimulation from

Ach

Continuous contraction of muscle fiber

Drugs stimulating neuromuscular transmission

•Significance…..? Treating weak or paralyzed muscles

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Motor unit

• Motor neuron, axon terminal and muscle fibers together called as motor unit

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• Muscles involved in fine movements- less muscle fibers in motor unit

ex: movement of eyes- ocular muscles• Muscles involved in coarse movements- more

muscle fibers in motor unit ex: flexion – leg muscles

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Recruitment of motor units

• Process by which more and more motor units are put into action

• Force of contraction increases

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Applied physiology

1. Myasthenia gravis - autoimmune disorder - antibodies for Ach receptors

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1. Eaton lambert syndrome - autoimmune disorder of NMJ - antibodies- calcium channels in axon

terminal

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Question of previous year

• Neuromuscular junction- (5m)- aug 2006• Draw a neat diagram of neuromuscular

junction. Describe the transmission of impulse across neuromuscular junction- (10m)- jan 2008

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THANK YOU