BIOL 153 Lecture Notes - Peristalsis, Vagus Nerve, Pylorus
Document Summary
The initial response of the stomach to filling is to relax. Receptive relaxation is a reflex involving the swallowing center of the brainstem and vagus nerve that causes the stomach to relax when food is in the esophagus. Adaptive relaxation reflex is activated when the stomach is filling. Stretch receptors on the stomach wall respond, and cause the stomach to dilate. Plasticity of the stomach allows it to respond to stretch without greatly increasing its tension and contracting expulsively. In the wall of the stomach are pacemaker cells which slowly depolarize and repolarize at a rate of about 3 per minute (called the basic electrical rhythm or. On their own, the depolarization"s do not reach threshold and no muscle contraction occurs. When outside stimulus arrives (stretch is the most important of these), threshold is reached, action potentials are fired, and muscle contraction occurs.
