Mass Movements by the Gastrocolic and Duodenocolic Reflexes

Initiation of Mass Movements by the Gastrocolic and Duodenocolic Reflexes 

The appearance of mass movements after meals is caused at least partially by gastrocolic and duodenocolic reflexes. These reflexes result from distension of the stomach and duodenum. They can take place, although with decreased intensity, when the autonomic nerves are removed therefore, it is probable that the reflexes are basically transmitted through the myenteric plexus, although reflexes conducted through the autonomic nervous system probably reinforce this direct route of transmission. 

It is likely that the hormone gastrin, which is secreted by the stomach antral mucosa in response to distension, also plays some role in this effect because gastrin has an excitatory effect on the colon and an inhibitory effect on the ileocecal valve, thus allowing rapid emptying of ileal contents into the cecum. This in turn elicits increased colonic activity. 

Irritation in the colon can also initiate intense mass movements. For example, a person who has an ulcerated condition of the colon (ulcerative colitis) frequently has mass movements that persist almost all of the time. 

Mass movements are also initiated by intense stimulation of the parasympathetic nervous system or simply by overdistension of a segment of the colon. 

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