NMJ Flashcards
Where is the NMJ found?
The junction between the CNS and the muscle cell itself
What are alpha motor neurons and what gives rise to them?
Neurons that receive information from upper motor neurons of the brain, the dorsal root gives rise to AMN
What is a motor unit and what does it do?
Alpha motor neuron + muscle = motor unit
Communicates with muscle fibre at NMJ
What are interneurons and where are they found?
Neurons with short projections that don’t travel out of where the cell body is. They control activity of cells in precise locations. They are found between afferent and efferent neurons.
What is acetylcholine’s role at the end plate?
ACh binds to a receptor on a post synaptic membrane - the end plate. Ligand gates ion channels open –> Na+ and K+ channel opens –> Na+ influx, K+ efflux –> depolarisation of end plate to -20mV
What is myasthenia gravis and how is it treated?
An autoimmune disease which makes antibodies against nACH receptors, when they bind they interfere with function and degrade NMJ.
Treated with neostigmine which inhibits acetylcholinesterase which increases the concentration of ACh at the NMJ
What are the 3 types of anticholinesterase drugs?
1) Thyostigmine - used in glaucoma
2) Neostigmine - used in myasthenia gravis
3) DDT and Sarin - pesticides/poison gas
What is calcium’s role with the release of ACh?
Calcium is involved with depolarisation of the cell as the action potential invades:
AP opens gated Ca2+ channels –> Ca2+ enters nerve terminal –> vesicles fuse with presynaptic membrane –> ACh is released
Why is ACh needed at the NMJ?
A large depolarisation is needed to reach threshold which is why ACh is released
What does botulinum toxin do?
Blocks the release of ACh which stops small contractions from happening and smooths the skin
What does hemicholinium do?
Blocks choline uptake
What does tubocurine do?
Blocks the receptor which gives non depolarising muscle paralysis
What does suxamethonium do?
Blocks depolarising agents
