The most important hormone that increases gallbladder contraction after a fatty meal is:

Ans. c. CCK (Ref: Ganong 23/e p443-446)Cholecystokinin (CCK) increases gallbladder contraction after a fatty meal.Cholecystokinin (CCK):Stimulation of pancreatic enzyme secretionQContraction of the gallbladderQRelaxation of the sphincter of OddiQGastrin:Produced by G cells in the antral portion of gastric mucosaQ.It mainly stimulates the secretion of gastric acid and pepsin from stomachQStimulates growth of mucosa of the stomach and the small and large intestinesQSecretin:It is produced by the S cells in the glands of the mucosa in the upper portion of the small intestine.It mainly increases the secretion of bicarbonateQ by the ductal cells of the pancreas and biliary tract.GIP:It is produced by K cells in the mucosa of duodenum and jejunum.It inhibits gastric secretion and motilityQ ('gastric inhibitory peptide').It also stimulates insulin secretion from the pancreasQAlso termed as 'glucose-dependent insulinotropic polypeptide'.Cholecystokinin (CCK)Secreted by the 'I' cells in the mucosa of the upper small intestine.Most important actions of Cholecystokinin (CCK)Stimulation of pancreatic enzyme secretionQContraction of the gallbladderQRelaxation of the sphincter of OddiQCCK also augments the action of secretin in producing secretion of an alkaline pancreatic juiceInhibits gastric emptying, exerts a trophic effect in the pancreas, increases the synthesis of enterokinase, and may enhance the motility of the small intestine and colon.Gastrin and CCK can also stimulate glucagon secretion.Two CCK receptors have been identifiedCCK-A receptors are primarily located in the peripheryQBoth CCK-A and CCK-B receptors are found in the brainQ.Both activate PLC, causing increased production of IP3 and DAG.The secretion of CCK is increased by the contact of the intestinal mucosa with the products of digestion, particularly peptides and amino acids, and also by the presence of fatty acids in the duodenum, containing more than 10 carbon atoms.