carotid body

a small area of specialized reddish-coloured tissue situated one on either side of the neck where the common CAROTID ARTERY branches to form the internal and external carotids. It is sensitive to chemical changes in the blood, containing CHEMORECEPTORS that respond to oxygen, carbon dioxide and hydrogen levels. If the oxygen level falls, impulses are transmitted to the respiratory centres in the brain, resulting in an increase in the rate of respiration and heartbeat.