This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 3, Subject name: Physiology
Concerning the central chemoreceptors, True is: 
Select and explain. 
A. They are located near the dorsal surface of the medulla, B. They respond to both the PCO2 and the PO2 of the blood, C. They are activated by changes in the pH of the surrounding extracellular fluid, D. For a given rise in PCO2, the pH of cerebrospinal fluid falls less than that of blood
C: They are activated by changes in the pH of the surrounding extracellular fluid
Answer: C: They are activated by changes in the pH of the surrounding extracellular fluid 
Explanation: The central chemoreceptors are located near the ventral surface of the medulla; They do not respond to the PO2 of blood; for a given rise in PCO2 , The CSF pH falls more than that of blood because the CSF has less buffering. The bicarbonate concentration of the CSF can affect the output of the Central Chemoreceptors by buffering the changes in pH.