Neuromuscular junction. Fluorescent confocal light micrograph of the junction between a nerve cell and a muscle (not seen). The axon of the nerve cell (neuron) has been tagged with a blue dye. The axon ends at end plates, which form junctions called synapses with the muscle cells. The end plates have been dyed red here by tagging them with the snake venom alpha-bungarotoxin, which binds to them. When a nerve signal reaches the synapse, it causes the synaptic vesicles to rupture, releasing the neurotransmitter acetylcholine. The protein synaptophysin, found in the vesicles, is dyed green. Acetylcholine binds to receptors on the muscle cells, causing them to contract. Magnification: x120 when printed 10cm wide.