What is the neuromuscular junction?
Synapse between LMNs and muscle fibres
Which horn of the spinal cord contains motor neurons?
Anterior (ventral horn)
What is a motor end plate?
The muscle-end of the neuromuscular junction
Each motor neuron may supply (one / many) muscle(s).
Each muscle is supplied by (only one / many) motor neuron(s).
Which neurotransmitter passes into the synaptic cleft of the NMJ in response to an action potential?
Which ions are involved in the wave of depolarisations along a nerve axon?
Which ion triggers the release of neurotransmitter into the synaptic cleft of the NMJ?
Which enzyme clears up remaining ACh from the synaptic cleft?
Which toxin occupies ACh receptors in the synaptic cleft, preventing muscle contraction?
'flying death', poison arrows etc.
Which receptor is blocked by tubocurarine?
What happens as a result?
Muscle paralysis (inc. respiratory)
Which poison inhibits acetylcholinesterase, causing muscle paralysis and death?
What cannot be released if there is a problem with the Ca2+ channels of the pre-synaptic neurons involved in NMJs?
What is botulism?
Infection by Clostridium botulinum
Which produces Botulinum toxin
What is the effect of botulinum toxin?
Blocks ACh release at pre-synaptic terminal
How do the following nerve agents affect the neuromuscular junction?
c) Botulinum toxin?
a) ACh receptor antagonists
b) Acetylcholinesterase inhibitor
c) Blocks secretion of ACh at pre-synaptic terminal
Name an autoimmune disease which affects the neuromuscular junction at the
b) pre-synaptic end?
a) Myaesthenia gravis
b) Lambert-Eaton syndrome
What is the main symptom of Lambert-Eaton syndrome?
What condition is Lambert-Eaton syndrome associated with?
Small cell lung cancer
What antibodies are produced in Lambert-Eaton syndrome?
Ca2+ channel antibodies
So not as much ACh is released into NMJ, causing muscle weakness
The drug 3-4-diaminopyridine is used to treat symptoms of Lambert-Eaton syndrome.
How does it work?
Blocks K+ channels
So action potential lasts for longer, more Ca2+ has the chance to enter the pre-synaptic terminal and more ACh can be secreted into the NMJ
What is a rare post-synaptic disorder causing muscle weakness and fatigue?
Myaesthenia gravis is an ___ disease.
When does the incidence of myaesthenia gravis peak?
What is the pathophysiology of myaesthenia gravis?
Autoantibodies BIND TO ACh receptors of neuromuscular junction
Resulting in muscle weakness and fatigability
Which antibodies are seen in 90% of patients with myaesthenia gravis?
ACh receptor antibodies
Which immune organ undergoes hyperplasia in myaesthenia gravis?
Particularly in young people
(Men / women) tend to develop myaesthenia gravis.
What is the course of weakness seen in myaesthenia gravis?
Which muscles tend to be affected in myaesthenia gravis?
Bulbar muscles (chewing, speaking, swallowing)
What tends to cause death in late myaesthenia gravis?
Respiratory muscle weakness