Neuromuscular Junctions Flashcards
Where is the cell body of the alpha motor neurone found?
Ventral horn of spinal cord
What are the 4 parts of a skeletal NMJ?
Terminal bouton
Synaptic vesicles
Synaptic cleft
End plate region (folded)
What are active zones of the terminal bouton?
Regions that vesicles containing neurotransmitter substances bind to before exocytosis
How is ACh formed in the bouton?
[comprises, site, enzyme]
Combined with acetyl CoA
In cytoplasm
By enzyme choline acetyltransferase
What type of receptors on the post-synaptic membrane are activated by the diffused ACh?
Nicotinic ACh receptors
Influx of which ion causes exocytosis of ACh into the synaptic cleft?
Ca++
What is the structure of the nicotinic ACh receptors on the muscle end plate?
Glycoprotein pentamer
α1)2 β1 δ ε
What is the end plate potential, e.p.p?
Depolarisation of muscle end plate
INflux of Na+, efflux of K+
What is a quantum of neurotransmitter?
Amount of ACh contained in each vesicle
What is a miniature e.p.p? (m.e.p.p)
Electrical response to one quantum of neurotransmitter
- e.p.p is a summation of m.e.p.ps
What must happen before a muscle contracts?
e.p.p must exceed the threshold and trigger an action potential
How does an action potential cause contraction of the skeletal muscle?
Enters T tubules
Triggers release of Ca++ from closely related sarcoplasmic reticulum
Ca++ interacts with troponin to form cross bridges…
Which enzyme is responsible for the termination of the e.p.p generated by ACh on the end plate membrane?
Acetylcholinesterase (AChE)
How does AChE work?
Hydrolyses ACh to choline + acetate
Name 5 conditions wherein there is defective NMJ transmission
Neuromyotonia
Lambert-Eaton Myasthenic Syndrome (LEMS)
Myasthenia gravis (MG)
Botulin toxin
