Transcription: Vomiting can be triggered by nerve signals from the digestive system, balance organs or chemical sensors activated by stimulants or toxins in the bloodstream. These nerve signals can also be triggered by a purely psychological reaction of disgust. The nerve signals activate the vomiting center in the brain stem, which sends nerve impulses to the stomach, the esophagus and muscles in the abdominal region. In a response called reverse peristalsis, waves of muscular contraction in the stomach and esophagus sends stomach contents up the digestive tract and out through the mouth. Simultaneous contr ...