DON FAWCETT / SCIENCE PHOTO LIBRARY DON FAWCETT / SCIENCE PHOTO LIBRARY
Synaptic junctions. False-colour scanning electron micrograph (SEM) showing the junction sites, also known as synapses, between motor nerve fibres (pale yellow) and skeletal muscle fibres (magenta). Synapses contain small vescicles loaded with neurotransmitters which are released in response to electrical impulses travelling from the neurones of the central nervous system. In the case of nerve fibres connected to skeletal muscle fibres the neurotransmitter involved is known as acetylcholine. This neurotransmitter is also released by those neurones that control the sweat glands and the heartbeat. Magnification unknown.
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