kemoreceptorer

Chemoreceptors, or kemoreceptorer, are sensory receptors that detect chemical changes in the environment or body fluids. In humans, they are key for monitoring respiratory gas tensions and acid–base status, helping regulate breathing and homeostasis. The main systems are peripheral chemoreceptors, located in the carotid and aortic bodies, and central chemoreceptors in the brainstem.

Peripheral chemoreceptors consist of glomus (type I) cells in the carotid bodies at the bifurcation of the carotid arteries and, to a lesser extent, in the aortic bodies along the aortic arch. The carotid bodies are especially sensitive to decreases in arterial PO2, increases in PCO2, and drops in pH. When stimulated, glomus cells depolarize and release neurotransmitters such as dopamine, acetylcholine, and norepinephrine onto afferent fibers of the glossopharyngeal nerve (CN IX) that project to the brainstem respiratory centers. The aortic bodies convey similar information via the vagus nerve (CN X). The resulting signals increase ventilatory drive to restore blood gas balance.

Central chemoreceptors are located in the ventrolateral medulla near the brainstem surface. They primarily sense pH changes in the cerebrospinal fluid, which reflect arterial CO2 levels. CO2 diffuses across the blood–brain barrier and, through pH changes, modulates neuronal activity to adjust ventilation. Central chemoreceptors are relatively insensitive to arterial oxygen levels.

Clinical relevance includes altered chemoreceptor sensitivity in chronic lung disease, altitude adaptation, and certain metabolic disorders. Abnormal chemoreception can contribute to respiratory instability in sleep disorders and other conditions.