Neuromuscular junction

NEUROMUSCU

LAR JUNCTION

Presented by:VARNAKA C H 1ST BNYS

INDEX

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

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

Structure

• 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

• 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

Neuromuscular transmission

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

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

Release of acetly choline

Action of acetly choline

Development of end plate potential

Devolpment of miniature end plate potential

Destruction of acetyl choline

Neuromuscular blockers

Drugs which prevent transmission of impulse across neuromuscular junction

significance..? useful in surgical and

trauma care

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

Neuromuscular stimulators

Inactivate Ach esterase

Repeated stimulation from

Ach

Continuous contraction of muscle fiber

Drugs stimulating neuromuscular transmission

•Significance…..? Treating weak or paralyzed muscles

Motor unit

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

• 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

Recruitment of motor units

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

• Force of contraction increases

Applied physiology

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

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

terminal

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

THANK YOU