<P> Chemoreceptors that regulate the depth and rhythm of breathing are broken down into two categories . </P> <Ul> <Li> central chemoreceptors are located on the ventrolateral surface of medulla oblongata and detect changes in pH of cerebrospinal fluid . They have also been shown experimentally to respond to hypercapnic hypoxia (elevated CO, decreased O2), and eventually desensitize . These are sensitive to pH and CO . </Li> <Li> peripheral chemoreceptors: consists of aortic and carotid bodies . Aortic body detects changes in blood oxygen and carbon dioxide, but not pH, while carotid body detects all three . They do not desensitize . Their effect on breathing rate is less than that of the central chemoreceptors . </Li> </Ul> <Li> central chemoreceptors are located on the ventrolateral surface of medulla oblongata and detect changes in pH of cerebrospinal fluid . They have also been shown experimentally to respond to hypercapnic hypoxia (elevated CO, decreased O2), and eventually desensitize . These are sensitive to pH and CO . </Li> <Li> peripheral chemoreceptors: consists of aortic and carotid bodies . Aortic body detects changes in blood oxygen and carbon dioxide, but not pH, while carotid body detects all three . They do not desensitize . Their effect on breathing rate is less than that of the central chemoreceptors . </Li>

Where is the primary chemoreceptor for co2 located