Similarities between the Oxygen Sensors of the Carotid Body and the Pulmonary Vascular Bed
Aerobic organisms, including man, usually live within a fairly narrow range of oxygen tensions. The partial pressure of oxygen, PO2, in the arterial circulation of normal individuals ranges from near 100 mm Hg, at sea level, to approximately 40 mm Hg in normal individuals at an altitude equivalent to the summit of Everest . Survival at higher or lower PO2 levels is not possible for more than brief periods. To achieve such tight control of oxygenation, man, and most aerobic organisms, is equipped with chemoreceptors which sense the oxygen level in the arteries or alveoli and, if hypoxia is detected, elicit a coordinated, multi-system response which attempts to correct hypoxemia or alveolar hypoxia. In humans, there are central chemoreceptors in the brain and peripheral chemoreceptors in the arterial vasculature (the carotid and aortic bodies). The carotid body monitors arterial oxygenation and increases its rate of sinus nerve discharge progressively as arterial PO2 is reduced from 150–50 mm Hg . It is responsible for virtually all of the increase in ventilation which occurs with hypoxemia in man, as demonstrated by the observation that patients lose hypoxic ventilatory drive following bilateral resection of the carotid bodies . The afferent signal from the carotid body is relayed to the brainstem by cranial nerve IX and stimulates the respiratory center in the brainstem, resulting in an increased volume and rate of respiration which optimizes arterial oxygen content.
KeywordsPulmonary Artery NADPH Oxidase Carotid Body Oxygen Sensor Mitochondrial Electron Transport Chain
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