In the physiological bicarbonate blood buffer system (CO2 + H2O <=> H2CO3 <=> H+ + HCO3-), how does the body immediately compensate for acute metabolic acidosis (excess H+)?
Answer and explanation
Correct answer: B. The respiratory center increases alveolar ventilation (hyperventilation) to blow off CO2
In metabolic acidosis, excess H+ drives the equilibrium: H+ + HCO3- -> H2CO3 -> H2O + CO2. Central and peripheral chemoreceptors detect the lower pH and stimulate rapid hyperventilation (Kussmaul breathing). Exhaling CO2 reduces arterial PCO2, driving the equilibrium further to the left and restoring the [HCO3-]/PCO2 ratio and blood pH toward normal (respiratory compensation).
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