The production of gastric juices in the human digestive system is constant but their secretion is also simulated. The Neutral and hormonal mechanisms generally regulate the secretion of gastric juices from the gastric glands. The three phases in the simulation of gastric secretion are the Cephalic phase, the Gastric phase and the Intestinal phase. Psychological factors like sadness or fear can also affect the secretion of gastric enzymes.