Either of a pair of collections of neurons (i.e. nuclei, sense 2) in the medulla oblongata in the brain that control the regularity of breathing. They are an important subcentre of the ventilation centre in the brain, and constitute the dorsal respiratory group. The neurons receive information from stretch receptors in the bronchial tubes and chemoreceptors in the carotid bodies and generate impulses that pass down the phrenic nerve to the diaphragm, causing it to contract (see inspiration). They alter the basic breathing rhythm in response to the physiological requirement of the body for oxygen.