Chemoreceptors in respiration. Illustration showing a woman and the chemoreceptors (chemosensors, small, blue, oval) in the chest and brain that are involved in the regulation of breathing. Chemoreceptors are sensory receptors that receive a chemical signal and convert (transduce) it into a nerve signal. Certain chemoreceptors, known as acid-sensing ion channels (ASICs), detect the level of carbon dioxide (CO2) in the blood and send signals to the respiratory centre in the medulla of the brain in order to increase breathing rate and lung volume when CO2 levels are high. Chemosensitive cells are shown in the heart's aortic arch, the carotid arteries in the neck, and the respiratory centre in the brain. For this illustration with labels, see image C027/7791.