Britannica Sources used in this answer

How does carbon dioxide in arterial blood affect carotid body activity?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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.

The carotid body acts as a peripheral chemoreceptor that monitors arterial blood composition. When the partial pressure of carbon dioxide in arterial blood rises, the activity of the carotid body increases linearly.1

The carotid body is sensitive to these fluctuations and responds more effectively to rapid changes in carbon dioxide levels than to slow ones. As metabolic rates increase, the resulting oscillations in carbon dioxide levels are detected by the carotid body, allowing the brain to adjust ventilation accordingly.1

At the cellular level, it is believed that hypercapnia—an excess of carbon dioxide—triggers the release of neuroactive substances, such as acetylcholine or catecholamines, from type I cells. These substances then stimulate the sensory nerve fibers that communicate with the brain's respiratory centers. Notably, the mechanisms used by the carotid body to sense carbon dioxide appear to be distinct from those used to detect hypoxia.1