Which of the following does NOT respond to pO2 levels?

The central chemoreceptors primarily respond to changes in carbon dioxide (pCO2) levels and the resultant changes in pH of the cerebrospinal fluid rather than directly to pO2 levels. They play a critical role in the regulation of breathing by detecting the concentration of carbon dioxide in the blood; an increase in pCO2 leads to a decrease in pH, which triggers an increase in ventilation.

In contrast, peripheral chemoreceptors (located in the carotid bodies and aortic bodies) respond to reductions in pO2 levels, while baroreceptors are sensitive to changes in blood pressure, and medullary chemoreceptors also indirectly respond to changes in pCO2 rather than pO2. By differentiating the specific roles of these receptors, it's clear that central chemoreceptors are unique in their lack of direct response to pO2, focusing instead on pCO2 and pH regulation.