CNRI / SCIENCE PHOTO LIBRARY CNRI / SCIENCE PHOTO LIBRARY
Synapse. Scanning electron micrograph (SEM) of a neuromuscular junction showing a motor neurone (vertical line) terminating on skeletal muscle fibres (across bottom frame). The axon of a motor neurone terminates in several branching fibres, each of which ends in an end plate, a cluster of small swellings, or boutons. When activated, the boutons release neurotransmitter chemicals from small vesicles. The neurotransmitters diffuse across the gap, or synaptic cleft, separating the axon and muscle and bind with receptors in the muscle cell. Magnification: x940 when printed at 10 centimetres tall.
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