Four major hormones of GI tract are (i) Gastrin Acts on gastric gland and stimulates the secretion of HCl and pepsinogen (ii) Secretin Acts on exocrine pancreas and stimulates secretion of water and bicarbonate ions (iii) CCK (Cholecystokinin) Acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzyme and bile juice (iv) GIP (Gastric Inhibitory Peptide) Inhibits gastric secretion and mortality