Final answer:
Central chemoreceptors stimulate ventilation to increase due to elevated levels of carbon dioxide in the blood, which in turn, raises hydrogen ion concentration and lowers pH, triggering respiratory regulation.
Step-by-step explanation:
The student's question asks about the stimuli for increased ventilation by central chemoreceptors. Central chemoreceptors in the medulla oblongata and CSF stimulate ventilation due to increased carbon dioxide (CO₂) levels. When the level of CO₂ in the blood rises, it diffuses across the blood-brain barrier into the extracellular fluid of the brain. This leads to an increase in hydrogen ions (H+) and a decrease in pH. The central chemoreceptors respond to this change by signaling the respiratory centers in the brain, which in turn initiate an increase in the rate and depth of breathing to expel more CO₂, thereby regulating the pH and CO₂ levels in the blood and CSF.