Which substance present in blood regulates contractions of stomach

There are two such hormones: they are enteroglucagon and vasoactive intestinal peptide. The former is secreted by the amine precursor uptake and decarboxylation (APUD) cells of the ileum and colon and the latter from intrinsic neurones found throughout the gastrointestinal tract. The walls also respond to the wave of peristalsis that starts with the swallowing mechanism.