Figure 3 - Schematic representation of esophageal contractions.

Swallowing (a) evokes a peristaltic wave of contraction that migrates smoothly from the striated to smooth muscle esophagus. Simultaneous electrical activation of all vagal efferent neurons (b) produces simultaneous contractions in the striated muscle esophagus, which would be expected based on the direct innervation of this muscle by the vagal efferent neurons. However, in the smooth muscle segment a peristaltic wave is induced. This is because intrinsic neurons activated by vagal efferent nerve stimulation are capable of evoking a peristaltic contraction without the need for centrally mediated sequencing. (Source: Goyal and Paterson,² with permission from the American Physiological Society.)