GI Tract: A Case Study

A vomiting reflex is triggered by stimulation of chemoreceptors in the upper GI tract. Mechanoreceptors in the wall of the GI tract are, also, activated. Both are activated by contraction and distension of the gut as well as by damage/injury. There is a center in the CNS that controls the emetic response. It is in the parvocellular reticular formation in the lateral medullary region of the brain. Afferent nerves to this center come from ABD splanchnic and vagal nerves, vestibule labyrinthine receptors, the cerebral cortex and chemoreceptors trigger zone. The chemoreceptors trigger zone is exposed to emetic stimuli such as pregnancy hormones and drugs. The efferent branches of cranial nerves V, VII, IX, the vagal nerve, and sympathetic trunk