Tetanus , tetanic muscle contraction ( dr. Greek. Τέτανος - numbness, cramp) - a state of prolonged contraction, continuous muscle tension that occurs when high-frequency nerve impulses arrive at it through a motor neuron. In this case, relaxation between successive single contractions does not occur, and their summation occurs, leading to a persistent maximum muscle contraction.
There are dentate and smooth tetanus. In dentate tetanus, each subsequent nerve impulse acts on the muscle that has begun to relax, and incomplete summation of contractions occurs. With a smooth tetanus with a larger amplitude, the impact of the pulse occurs at the end of the shortening period, which leads to a complete summation of contractions.