True Hormones

The 4 true hormones are Gastrin, CCK, Secretin, and GPI.
Gastrin, stimulates acid secretion, pepsinogen secretion, the pancreas, bile, gallbladder, and the intestine.

CCK stimulates pancreatic enzymes and bicarbonate secreation, gallbladder contraction, and release of bile into small intestine, inhibits gastric emptying due to byproducts of fats or proteins in small intestine. It also inhibits gastric acid secreation.

Secretin stimulates pancreatic secreation of bicarbonate and water, released by acid in the small intestine, it inhibits gastrci emptying and secretion of acid, increases biliary secretion of bicarbonate and water.

Gastric Inhibitory Peptide induces insulin secretion it also plays a role in fatty acid metabolism.

B.
The neurotransmitters transmit information quickly from one area of the body to another. They send messages in the form of hormones in the bloodstream and those hormones then regulate the functions of the GI tract.