Phase 1 is the cephalic phase: neural control of the GI tract. This is when we see, smell, think of food and our mouth waters. It’s us thinking about food and getting hungry. The parasympathetic branch stimulates digestion (think rest and digest from skye’s class, easy to remember). The sympathetic nervous system would be more of energy expenditure while parasympathetic is storage.
Phase 2 is the gastric phase: mechanical, endocrine, and neural control. This is when food enters the stomach, and its activated by stomach distension (when the stomach fills up and stretches because of the food that’s in it) as well as chemicals in the food. This stimulates nerves as well as hormones that help regulate digestion (endocrine factors). The gastric phase also has something called short reflexes. They’re neural reflexes that don’t go to the brain. It connects one part of the GI tract to another part so signals can be transmitted quickly. Long reflexes also happen in the gastric phase. They go via the medulla and the vagus nerve that can go to other parts of the GI tract but they are processed through the brain. Gastrin is a hormone that comes from G cells (involved in endocrine control). Note: ALL THREE OF THESE PHASES CAN BE INHIBITED
Phase 3 is the Intestinal phase: mechanical, endocrine, and neural control. This phase is stimulated by partially digested food that enters the small intestine. We see inhibition (negative feedback) the more acidic the intestine, the less contents are going to be ejected into the intestine. Hormonal control: gastrin released in the stomach and stimulatory effects of others.
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