When a nerve impulse comes to the end of the axon and reaches a terminal button, the terminal button releases a chemical courier called a neurotransmitter. Neurotransmitters are chemicals that carry messages across the synapse to a dendrite (and sometimes the cell body) of a receiving neuron. Like a boat that ferries passengers across a river, these chemical messengers move toward the shorelines of other neurons. The chemical mode of massage transmission that occurs between neurons is strikingly different from the means by which communication occurs inside neurons: Although messages travel in electrical from within a neuron, they move between neurons through a chemical transmission system.
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