the primary chemoreceptor for co2 is located at medulla oblongata.
where is the primary chemoreceptor for co2 located?
medulla oblongata
emesis is a defense mechanism controlled by the area postrema of the medulla oblongata. there are various sources of input to the vomiting center. receptors on the floor of the fourth ventricle of the brain represent the chemoreceptor trigger zone. the chemoreceptor trigger zone contains dopamine d2 receptors, serotonin 5-ht receptors, opioid receptors, acetylcholine receptors, and receptors for substance p. stimulation of different receptors are involved in different pathways leading to emesis. in the final common pathway, substance p, which activates the neurokinin-1 receptor, appears to be involved. additionally, the vagal and enteric nervous system inputs transmit information regarding the state of the gastrointestinal system. irritation of the gi mucosa by chemotherapy, radiation, distention, or acute infectious gastroenteritis activates the 5-ht receptors of these inputs. it is now widely known that cytotoxic chemotherapeutic agents cause a detectable increase in blood levels of serotonin (5-ht) and its major metabolite, 5-hydroxyindoleacetic acid (5-hiaa). the presence of these chemicals in the blood activate 5-ht receptors in the chemoreceptor trigger zone, in turn releasing substance p, which activates nk receptors to cause an emetic response (vomiting).
chemotherapy-induced nausea and vomiting
paraganglion





























a paraganglion (pl. paraganglia) is a group of non-neuronal cells derived of the neural crest. they are named for being generally in close proximity to sympathetic ganglia. they are essentially of two types: chromaffin or sympathetic paraganglia made of chromaffin cells and nonchromaffin or parasympathetic ganglia made of glomus cells. they are neuroendocrine cells, the former with primary endocrine functions and the latter with primary chemoreceptor functions.
paraganglion