Peripheral and central chemoreceptors may both contribute to the increased ventilation that occurs as a result of which of the following?

The central chemoreceptors located on or near the ventral surface of the medulla cause an increase in ventilation in response to an increase in PacO2 and to a lesser extent to a decrease in aerial pH because the blood brain barrier is relatively impermeable to hydrogen ions. The peripheral chemoreceptors in the carotid bodies cause an increase in ventilation in response to an increase in PacO2 a decrease in aerial pH, and a decrease in PaO2. Neither the central chemoreceptors nor the carotid bodies are stimulated by a decrease in aerial blood pressure or O2 content.