Neuromuscular mechanisms of primary peristalsis.

Primary peristalsis of the esophagus is initiated by the act of swallowing. Control of the orderly contraction must take into account coordination of the activity in the esophageal body with the sphincters at either end, integration of activity between the striated and smooth muscle portions of the esophagus, and the central and peripheral neural and muscular control mechanisms present. Peristalsis in the striated section is directed by sequential vagal excitation arising in a brainstem "Central Program Generator." Peristalsis in the smooth muscle section involves the interaction of central and peripheral neural mechanisms and probably the interaction between these neural mechanisms and smooth muscle properties. Coordination of activity between the striated and smooth muscle portions has similar multifaceted neural and mechanical components. In the smooth muscle, 2 main neural mechanisms, a cholinergic excitatory one and a nonadrenergic, noncholinergic (NANC) inhibitory one interact together and with central and local influences to regulate the amplitude, velocity, and direction of propagation of the peristaltic contraction.