neuromuscular junction
TRANSCRIPT
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