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summation sum·ma·tion (sə-mā'shən)
The process by which multiple or repeated stimuli can produce a response in a nerve, muscle, or other part that one stimulus alone cannot produce.
in physiology, the additive effect of several electrical impulses on a neuromuscular junction, the junction between a nerve cell and a muscle cell. Individually the stimuli cannot evoke a response, but collectively they can generate a response. Successive stimuli on one nerve are called temporal summation; the addition of simultaneous stimuli from several conducting fibres is called spatial summation.