Part of the vertebrate brainstem, derived from the hindbrain, that is continuous with the spinal cord. Its function is to regulate the autonomic pathways controlling breathing, heartbeat, blood pressure, digestive movements, and other involuntary processes. Nerve signals from the peripheral nervous system via the spinal cord are relayed by the medulla to the midbrain and forebrain, and the medulla gives rise to many of the cranial nerves. Dorsal respiratory neurons in the medulla send nerve impulses to control breathing movements of the diaphragm (see ventilation centre). These neurons receive impulses from chemoreceptors on the surface of the medulla that respond to the pH of their surroundings, which reflects the partial pressure of carbon dioxide in the blood. They also have inputs from oxygen-sensitive chemoreceptors in the major blood vessels, and from higher centres in the brain. The medulla’s cardiovascular control centre regulates the autonomic nervous system that governs heart rate and blood pressure. It integrates inputs from the medulla’s pH chemoreceptors and the oxygen sensors in the great vessels, as well as from pressure receptors (baroreceptors) in the aorta and carotid artery, and from higher brain centres responsible for stress or emotions.