ABSTRACT
This chapter deals with stimulation using current pulses and alternating current, and demonstrates that excitation requires the sudden removal of a critical charge from the membrane of an excitable cell. G. G. Weiss and L. Lapicque were the first to enunciate the fundamental law of excitation, which states that the shorter the duration of the current pulse, the higher the current required stimulating. Anodal stimulation is well known that positive-polarity pulses will stimulate excitable tissue. Before discussing the response to a train of pulses or alternating current, it is necessary to establish the concept of refractoriness. With the knowledge that both anodal and cathodal current can stimulate and that the refractory period of a cell will allow repetitive excitation, it is easy to see that sinusoidal alternating current can stimulate excitable tissue. The skeletal muscle response to a single stimulus is called twitch; the response to a train of stimuli is called a tetanic contraction or tetanus.
