The wall of the active part of the stomach secretes among others hydrochloric acid. This serves to denature proteins, to activate digestive enzymes and kill bacteria. This secretion has an accelerator: It is an enzyme called gastrin which is secreted by the pyloric region. The production of gastrin is governed by three factors: 1. Nerve impulses (nervus vagus), anxiety, nervousness, injury, burns, ingestion of drugs such as cortisone and reserpine, cigarettes, coffee and tea promote the production of gastrin. 2. The concentration of hydrochloric acid. If the latter is excessive, gastrin production ceases, otherwise, it increases. 3. The nature of food: protein-rich food or plant fibers, highly spicy food, too hot or too cold, alcohol and poisons produce increased gastrin secretion. Excess gastrin production increases acidity in the stomach which is often the cause of gastites or ulcers which, in turn, disrupt the secretion of gastrine. Medications called antacids, for instance magnesium oxide, aluminum oxide or sodium hydrogencarbonate neutralize excess hydrochloric acid: Find ionic equation for the reaction of each antacid with hydrochloric acid!