physiology of neuro muscular junction

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physiology of neuro muscular junction, working of neurons and muscle

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Anatomy ,Physiology of Neuromuscular Junction with Neuromuscular transmission Dr sheetal panwar asst prof department of physiology R.D.G.M.C.: 

Anatomy ,Physiology of Neuromuscular Junction with Neuromuscular transmission Dr sheetal panwar asst prof department of physiology R.D.G.M.C.

The site at which motor neuron attaches on the muscle cell is known as the neuromuscular junction : 

The site at which motor neuron attaches on the muscle cell is known as the neuromuscular junction

NEUROMUSCULAR JUNCTION : 

NEUROMUSCULAR JUNCTION Each muscle fibre is connected to a nerve fibre branch coming from a nerve cell. These nerve cells are called motor neurons , and extend outward from the spinal cord The motor neuron and all the muscle fibres it innervates are called a motor unit . Stimulation from motor neurons initiates the contraction process.

A.Motor neuron originate in the ventral horn of the spinal cord or brain stem. B.As nerve approaches to muscle fiber it divided into branches that innervate many individual muscle fiber . C.Each muscle receive only one synapse . D.Nerve terminal covered by a sachwann cell, has vesicle clustered which are active zones towards its synaptic side and mitochondria and microtubules on other side .: 

A.Motor neuron originate in the ventral horn of the spinal cord or brain stem. B.As nerve approaches to muscle fiber it divided into branches that innervate many individual muscle fiber . C.Each muscle receive only one synapse . D.Nerve terminal covered by a sachwann cell, has vesicle clustered which are active zones towards its synaptic side and mitochondria and microtubules on other side .

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3 types of cells that constitute the synapse- Motor neuron Muscle fiber Schwann cell

Synaptic cleft or gutter - 20 nm Muscle surface is corrugated and dence area on the shoulder of each fold containing Ach receptor . Sodium channels are present below the cleft through out the muscle membrane . Acetyl cholinesterase ,protein and proteoglycan is present in the cleft which stabilize the NMJ.: 

Synaptic cleft or gutter - 20 nm Muscle surface is corrugated and dence area on the shoulder of each fold containing Ach receptor . Sodium channels are present below the cleft through out the muscle membrane . Acetyl cholinesterase ,protein and proteoglycan is present in the cleft which stabilize the NMJ.

NEUROMUSCULAR JUNCTION: 

NEUROMUSCULAR JUNCTION At this junction, the sarcolemma forms a pocket known as the motor end plate The end of the motor neuron is not in direct contact with the muscle fibre but is separated by a short gap known as the neuromuscular cleft A nerve impulse reaching the end of the motor nerve stimulates the release of the neurotransmitter acetylcholine which diffuses across the synaptic cleft and binds to the receptor sites on the motor end plate

NEUROMUSCULAR JUNCTION: 

NEUROMUSCULAR JUNCTION This causes an increase in permeability of sarcolemma to sodium and sodium diffuses into muscle fibre resulting in a depolarisation called the end-plate potential (EPP) This EPP is usually large enough to exceed the threshold that is the signal to start the contractile process.

Nerve synthesized Ach vesicle stimulation of nerve migration of vesicle on the surface of nerve Ruptured and discharge Ach into cleft . Ach R in end plate of Ms respond by opening of Na+ channel Depolarization of Ms . End plate potential is created Contraction : 

Nerve synthesized Ach vesicle stimulation of nerve migration of vesicle on the surface of nerve Ruptured and discharge Ach into cleft . Ach R in end plate of Ms respond by opening of Na+ channel Depolarization of Ms . End plate potential is created Contraction

Mechanism of neuromuscular Block Depolarising or Non-competitive Block. Non-depolarising or Competitive Block .: 

Mechanism of neuromuscular Block Depolarising or Non-competitive Block. Non-depolarising or Competitive Block .

Depolarising or Non-competative Block. Drug occupies the alpha subunit of a receptor binding site to produce depolarization ,and remain attached for longer than acetylcholine ,rendering the receptor insensitive to further stimulation .: 

Depolarising or Non-competative Block. Drug occupies the alpha subunit of a receptor binding site to produce depolarization ,and remain attached for longer than acetylcholine ,rendering the receptor insensitive to further stimulation .

Non-depolarising or Competative Block . Drug competes with acetylcholine to occupy the receptor –binding site but does not produce any initial stimulation or depolarisation.: 

Non-depolarising or Competative Block . Drug competes with acetylcholine to occupy the receptor –binding site but does not produce any initial stimulation or depolarisation.

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Depolarising or Non- Competative Block. Non- depolarising or Competative Block Muscle Fasciculation seen . No muscle fasciculation . Ms is unresponsive to electrical or mechanical stimuli, repolarisation does not happen until phase 2 block develop. Relaxed muscle remain responsive to electrical or mechanical stimuli . Relaxed muscle remain responsive to electrical or mechanical stimuli . Slow in onset and slow dissociation at receptors Block is not reversed by Neostigmine or other anticholinesterase . Reversed by anticholinesterase .

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No fade and no post-tetanic facilitation seen Fade and post- tetanic facilitation seen and followed by exhaustion . Potentiated by Isoflurane ,respiratory alkalosis ,hypothermia and magnesium Potentiated by volatile agent, acidosis ,Mg and hypokalemia. Antagonised by acidosis and non- depolarising . Effect reduced by suxamethonium Repeated or continuous use leads to phase 2 block . Mild cooling antagonises their effects ,but further cooling below about 33 C potentiate them

THANK YOU : 

THANK YOU