Final answer:
The vagus nerve (CN X) monitors the aortic body and arch chemoreceptors and baroreceptors. It is instrumental in the autonomic control of various thoracic and upper abdominal organs and contributes to cardiovascular and respiratory regulation.
Step-by-step explanation:
The cranial nerve that monitors the aortic body and arch chemo- and baroreceptors is the vagus nerve (CN X). While baroreceptors from the carotid arteries have axons in the glossopharyngeal nerve, those from the aorta are connected to the vagus nerve. The vagus nerve, as the tenth cranial nerve, is responsible for the autonomic control of organs in the thoracic and upper abdominal cavities.
The role of the vagus nerve is not limited to baroreceptor signaling; it also encompasses many parasympathetic functions, including reducing heart rate, relaxing bronchial tubes, and activating digestive function through the enteric nervous system, as managed by the brain stem nuclei such as the solitary nucleus and the dorsal motor nucleus of the vagus nerve.
In addition, the vagus nerve and its associated brain stem nuclei also receive critical chemoreceptor signaling related to the levels of oxygen, carbon dioxide, and hydrogen ions (pH) in the blood, further contributing to cardiovascular and respiratory homeostasis.