Gastro intestinal Reflexes
The motility of the bowel is regulated and controlled by reflexes which all work together. The two main reflexes are the gastro-colic reflex and the defaecation reflex.
A Gastro-colic reflex is when the distention of the stomach while eating or immediately after a meal which triggers mass movement in the colon. It is strongest after the first meal of the day – breakfast - and the urge to defaecate is often felt after this. It is a good time to use the toilet for a bowel movement even if desire is not felt.
A defaecation reflex is an involuntary response of the lower bowels to various stimuli and it can promote or even inhibit a bowel movement.
Clinical practice point. It is important to understand this for biofeedback treatments.
These reflexes are under the control of the central nervous system.
The two main defaecation reflexes are known as the intrinsic myenteric defaecation reflex and parasympathetic defaecation reflex.
Intrinsic myenteric defaecation reflex – stimulates contraction of the smooth muscle of the descending colon, sigmoid colon and rectum
Parasympathetic defaecation reflex - when triggered this reflex moves faeces from the descending colon, sigmoid colon into the rectum, and with this increase the internal sphincter starts to relax. The force triggered by the parasympathetic defaecation reflex can be powerful enough to result in defecation, despite conscious efforts to keep the external anal sphincter constricted
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