Three other types of cells round out the team. Delta cells are part of the feedback loop in the pancreas; remember that almost all biologic processes have a built-in "off switch" like this. These cells produce somatostatin, which, among other actions, turns off the alpha and beta cells. PP cells may sound like code for preschool bathrooms, but these cells contain pancreatic polypeptide and prevent pancreatic enzymes from being secreted into the gut after a protein meal, fasting and exercise. Finally, a few epsilon cells contain the hormone ghrelin, which stimulates our hunger and very often causes us to eat like a bear in a stream of salmon.