Regulation of the cardiovascular system, the respiratory system and the gastrointestinal tract (GIT) is represented in the lower brain stem. These control systems require precise coordination and are closely integrated, which is reflected in the anatomy and physiology of the neural substrates of these control systems. Included in this integration are the final autonomic pathways, the enteric nervous system and the spinal autonomic circuits. The circuits in the medulla oblongata are under the control of the upper brain stem, hypothalamus and telencephalon. Neurons involved in regulation of arterial blood pressure and respiration are situated in rostrocaudally organized columns of neurons in the ventrolateral medulla (VLM). The rostral VLM is a sympathetic cardiovascular premotor nucleus mediating reflexes to sympathetic cardiovascular preganglionic neurons such as arterial baroreceptor, arterial chemoreceptor and other reflexes. The caudal raphe nuclei of the medulla oblongata are involved in thermoregulation and regulation of energy balance. The respiratory pattern in cardiovascular neurons is generated by the "common cardiorespiratory network" in the VLM. Neural control of the GIT by the lower brain stem is exerted by multiple reflex circuits consisting of vagal afferents from the GIT, neurons in the nucleus tractus solitarii and parasympathetic preganglionic neurons projecting to the GIT.