Cephalic phase

The cephalic phase of gastric secretion occurs even before food enters the stomach, especially while it is being eaten. Preparation for digestion begins with the producing saliva and enzyme production. Mechanical and chemical digestion then starts to occur in the mouth as food is chewed, and mixed with saliva in the mouth, before being further broken down through mechanical and chemical processing in the stomach.

It results from the sight, smell, thought, or taste of food, and the greater the appetite, the more intense is the stimulation. Neurogenic signals that cause the cephalic phase of gastric secretion originate from the cerebral cortex and in the appetite centers of the amygdala and hypothalamus.They are transmitted through the dorsal motor nuclei of the vagi and then through the vagus nerve to the stomach. This phase of secretion normally accounts for about 20 percent of the gastric secretion associated with eating a meal.