Point 11 Intro Pathway Deficit Note Clinical Taste Overview Problems Contents Anatomy

READ ON ONLY IF YOU ARE INTERESTED. NOT ON EXAM! There are chemoreceptors in the carotid and aortic bodies that affect respiration. The afferent information from the carotid and aortic bodies travel in C.N.s IX (carotid body; cell bodies in INFERIOR GANGLION IX) and X (aortic body; cell bodies in INFERIOR GANGLION X). The receptors in the carotid and aortic bodies respond to a decrease in arterial oxygen tension (P02) and an increase in arterial carbon dioxide (PCO2). For instance, an increase in PCO2 will result in an increase in the number of impulses traveling over C.N.s IX and X to the caudal nucleus solitarius. Neurons in nucleus solitarius project to the phrenic nucleus, which consists of a group of neurons in the ventral horn of the spinal cord from C3-C5. Axons arising from the phrenic nucleus comprise the phrenic nerve that innervates the diaphragm. Cells in nucleus solitarius also project to neurons in the spinal cord that innervate the intercostal muscles. Therefore, an increase in PCO2 will result in an increase in the depth and rate of breathing, while a decrease in PCO2 will have the opposite effect. This is NOT a course in respiratory or cardiovascular physiology! However, it is extremely important for you to remember that the brain stem, especially the medulla, is an important region for the control of respiration and cardiovascular functions. BILATERAL lesions of the caudal nucleus solitarius will result in major respiratory and cardiovascular problems that result in death.