Optimum(redirected from optima)
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in physiology, the strength or frequency of a stimulus at which an organ or tissue functions at maximum level of activity. The optimum phenomenon was described in 1886 by N. E. Vvedenskii. Using a neuromuscular specimen from a frog, he demonstrated that increasing to a certain limit the frequency or strength of a stimulus intensifies tetanus—the prolonged, continuous contraction of the muscle. The optimum phenomenon occurs because each succeeding stimulus affects the muscle during a period of increased excitability induced by the previous stimulus.