Respiratory centers are a collection of brainstem nuclei located in both the medulla and pons. They receive afferent information on the partial pressures of arterial oxygen, arterial carbon dioxide, and blood pH. This information is then used to regulate breathing rate, so that homeostasis can be maintained. The respiratory centers can be organized into four divisions: the inspiratory, pneumotaxic, apneustic, and expiratory centers, but only the pneumotaxic and apneustic centers are found within the pons.