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How do central chemoreceptors respond when carbon dioxide levels rise?

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A pine grosbeak with pink and gray plumage perches on a branch, eating red berries among autumn foliage. — Chemoreception Animals, such as this pine grosbeak, use chemoreception to respond to chemicals that can be tasted and smelled in their environments. Many of these chemicals affect behaviors such as food preference and defense.

Central chemoreceptors, located near the ventral surface of the medulla, play a critical role in the human respiratory system by responding to rising levels of carbon dioxide in the blood.1

When the partial pressure of carbon dioxide increases, it leads to a nearly linear increase in ventilation. Carbon dioxide influences this process by increasing the acidity of the fluid surrounding cells and by diffusing into cells, where it also increases intracellular acidity. While it remains unclear whether these receptors respond specifically to intracellular or extracellular changes, their activation serves as a powerful stimulant for breathing.1

Although these receptors are thought to be situated in the medulla, specific chemoreceptor cells have not been conclusively identified through microscopic examination. Some researchers suggest that the respiratory response in this region may result from direct interference with the excitatory and inhibitory inputs provided by nearby vasomotor neurons, which are involved in the regulation of blood pressure.1