Carotid Bodies

The carotid bodies are in an ideal position to monitor the oxygen content of the blood before it reaches the brain. Decrease in PO₂ (partial pressure of oxygen), as occurs at high altitudes or in pulmonary disease, activates the aortic and carotid chemoreceptors, increasing alveolar ventilation. The carotid bodies also respond to increased carbon dioxide (CO₂) tension or free hydrogen ions in the blood.

Diagram displaying right carotid artery and the position of the carotid body and its innervation.

The glossopharyngeal nerve (CN IX, perhaps with involvement of the vagus nerve) conducts the information centrally, resulting in reflexive stimulation of the respiratory centers of the brain that increase the depth and rate of breathing. The pulse rate and blood pressure also increase. With the increased ventilation and circulation, more oxygen is taken in and the concentration of CO₂ is reduced accordingly.