See D. Wiggens, Sameness and Substance (1980).
Chemical released by neurons to stimulate neighbouring neurons, allowing impulses to be passed from one cell to the next throughout the nervous system. A nerve impulse arriving at the axon terminal of one neuron stimulates release of a neurotransmitter, which crosses the microscopic gap (see synapse) in milliseconds to the adjoining neuron's dendrite. Many chemicals are believed to act as neurotransmitters. The few that have been identified include acetylcholine, dopamine, and serotonin. Some neurotransmitters activate neurons; others inhibit them. Some mind-altering drugs act by changing synaptic activity.
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Substance may refer to: