Electrical activity of GI smooth muscle 1.Resting potential 2.Slow wave or basic electric rhythm (BER) Basic electrical rhythm is the spontaneous rhythmic,subthreshold depolarization of the cell membrane in the gastrointestinal tractElectrical activity of GI smooth muscle 1. Resting potential 2.Slow wave or basic electric rhythm (BER) Basic electrical rhythm is the spontaneous rhythmic, subthreshold depolarization of the cell membrane in the gastrointestinal tract