This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Central Chemoreceptors are most sensitive to which of the following changes in blood? \nSelect and explain. \nA. |p CO2, B. |p CO2, C. |H +, D. |p O2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Central chemoreceptors are stimulated mainly by the |H+ concentration caused by increased pCO2 levels. Since H+ cannot easily cross the blood brain barrier, increase in the blood H+ concentration have little effect in stimulating central chemo receptors. Increase in blood p CO2 causes CO2 to diffuse the blood brain barrier with ease where it reacts with water to form carbonic acid. This carbonic acid in turn dissociates into H+ and bicarbonate ions. This H+ ions then have a potent stimulatory effect on the central chemo receptors. This question asks about the changes in blood that stimulates the central chemo receptors. So the correct answer is |p CO2 levels as H+ concentration in blood has little effect in stimulating the central chemo receptors. Ref: Textbook Of Medical Physiology By Khurana, Page 458', 'role': 'assistant'}]