Muscle: Neuromuscular Junction
At the neuromuscular junction, the motor neuron forms a flat branching plate called a 'motor end plate' (see picture). The myelin sheath stops just short of the branching presynaptic terminal.
Synaptic vesicles containing neurotransmitter (acetylcholine) are present in the presynaptic terminal . Stimulation of the nerve, causes release of acetylcholine into the synaptic cleft.
This diffuses across to the postsynaptic terminal, where it binds to acetylcholine receptors.
This results in depolarisation of the muscle fibre, causing it to contract.
The acetylcholine is then broken down by an enzyme called acetylcholinesterase, which is associated with the basement membrane of the synaptic cleft. This prevents continued stimulation of the muscle fibre.