Like other excitable cells, gastrointestinal smooth muscle cells maintain a electrical potential difference across their membranes. These partial depolarizations are equivalent to fluctuations in membrane potential of 5 to 15 mV. The frequency of slow waves depends on the section of the digestive tube - in the small intestine, they occur 10 to 20 times per minute and in the stomach and large intestine 3 to 8 times per minute. Slow wave activity appears to be a property intrinsic to smooth muscle and not dependent on nervous stimuli. Importantly, slow waves are not action potentials and by themselves do not elicit contractions.
Spike potentials are true action potentials that elicit muscle contraction.
They result when a slow wave passes over an area of smooth muscle that has been primed by exposure to neurotransmitters released in their vicinity by neurons of the enteric nervous system . One can now step back and understand how a particular pattern of motility is achieved. When a slow wave passes over this area of sensitized smooth muscle, spike potentials form and contraction results. The contraction moves around and along the gut in the coordinated manner because the muscle cells are electrically coupled through gap junctions.