Retroperistalsis
（重定向自Reverse Peristalsis）
Retroperistalsis is the reverse of the involuntary smooth muscle contractions of peristalsis. It usually occurs as a precursor to vomiting. Local irritation of the stomach, such as bacteria or food poisoning, activates the emetic center of the brain which in turn signals an imminent vomiting reflex. Food then moves in the opposite direction, often from the duodenum into the stomach.