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How do receptors monitor carbon dioxide levels in the blood?

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Compound eye — Senses Vespid wasps (Vespidae), similar to other insects, have compound eyes that consist of thousands of tiny optical units known as ommatidia, which contain light-sensitive photoreceptor cells.

The body monitors carbon dioxide levels through a feedback system involving two primary types of chemoreceptors that regulate breathing to maintain homeostasis.1

Peripheral Chemoreceptors

Located primarily in the carotid bodies in the neck and the aortic bodies near the aorta, these sensors monitor arterial blood. The carotid bodies are particularly sensitive to rapid fluctuations in the partial pressure of carbon dioxide. When carbon dioxide levels rise, type I cells in these organs release neuroactive substances—such as acetylcholine and catecholamines—which stimulate sensory nerves to signal the brain to increase ventilation.2

Central Chemoreceptors

Located near the ventral surface of the medulla in the brain, these receptors respond to changes in the partial pressure of carbon dioxide in their immediate environment. Carbon dioxide easily crosses into cells, where it increases acidity. While it is not fully understood if these receptors respond to the carbon dioxide itself or the resulting change in pH, they serve as a powerful stimulant for breathing.31

Together, these systems ensure that ventilation is adjusted to keep carbon dioxide at a precise, constant level, which also helps regulate blood pH.14