A 38-year-old man was brought by his wife as his snoring becomes louder soon after falling asleep, and is then interrupted by a long silent period during which no breathing (apnea) occurs. He was diagnosed as having Obstructive sleep apnea. Individuals with OSA awaken when the aerial hypoxemia and hypercapnia stimulate both peripheral and central chemoreceptors. The activity of the central chemoreceptors is stimulated by which of the following?

The response to hypoxia is mediated entirely by peripheral chemoreceptors; the response to hypercapnia and acidemia is mediated mainly (75%) by central chemoreceptors and paly (25%) by peripheral chemoreceptors. Central chemoreceptors are stimulated by a fall in pH of the cerebrospinal fluid (CSF) and the brain interstitial fluid. The magnitude of the stimulation is propoionate to the rise in hydrogen (H+) concentration. A rise in aerial PCO2 stimulates the central chemoreceptors.