The GI tract also receives input from the peripheral nervous system that act at the plexi to increase or decrease excitability of the smooth muscle. Most of the input is excitatory with little inhibitory input. In contrast to the vascular smooth muscle, parasympathetic innervation is excitatory while sympathetic is inhibitory. Only the entrance and exit points or the GI tract have skeletal muscle. Therefore once food enters the tract if is involuntary.
Propulsion is termed peristalsis and mixing, the pyloric pump or segmentation.
Chewing and swallowing Voluntary reflex with involuntary components. Pressure from food in mouth activates mechanoreceptors in mouth that reflexly inhibits muscles in jaw causing relaxation. Chewing is not necessary for digestion but assists with swallowing. Swallowing is initiated by passing food to back of mouth with the tongue. This originates in the esophagus and is stimulated by distension.