Neural regulation of mechanical digestion- CNS voluntary, ANS & ENS controlled involuntary movements

• The gastrointestinal [GI] tract is basically a muscular tube that contains and processes food as it moves from the mouth to the anus. • Mechanical digestive functions consist of both voluntary and involuntary muscle contractions and relaxation including: • Chewing and swallowing food. • Mixing and moving food throughout the GI tract. • Elimination of feces. • The propulsive and mixing movement of the smooth muscles in the digestive system are regulated by: • Hormonal feedback loops. • Neural feedback loops. Neural control of the mechanical movements in the GI tract comes from the: • CNS. • ANS (long) reflexes. • ENS (local) reflexes. • The CNS controls voluntary swallowing movements. • The presence of food is the stimulus for voluntary digestive movements. • ANS (long) neural reflexes include a CNS control center in the spinal cord or brain. • ANS neurons regulate involuntary smooth muscular movements. • The stimulus for many involuntary digestive movements is distension. • The response is either increased or decreased contraction of the muscularis. • ENS (or local) reflexes utilize the plexuses embedded in the wall of the GI tract. • ENS reflexes also control involuntary movements of the muscularis. • Mastication, or chewing, is a voluntary process, regulated by the CNS, and performed by muscles above and below the mandible. • Skeletal muscles elevate the mandible, closing the mouth and moving the mandible side to side to chew. • During chewing, food is: • Cut and ground by teeth. • Manipulated by the tongue, lips and cheeks. • Pushed toward the oropharynx.

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