The end-plate zone of muscle contains neuromuscular junctions. This simplified account of their structure and function is designed to aid an understanding of repetitive nerve stimulation testing and single-fibre electromyography, detailed later in the book. The anatomy of the synaptic bulb containing acetylcholine-filled vesicles is described. These are discharged into the synaptic cleft by the process of exocytosis. Small quantities which occur spontaneously produce end-plate potentials but larger quantities following depolarisation of the synaptic bulb will generate a muscle action potential.