The brain stem is the stalk of the brain below the cerebral hemispheres. It is the major route for communication between the forebrain and the spinal cord and peripheral nerves. It also controls various functions including respiration and regulation of heart rhythms.
Mostly enveloped by the cerebrum and cerebellum, the visible part of brainstem is shown in black.
The lower part of the brain stem is the medulla oblongata. The pons is a knob on the brainstem. Differentiation of the brain stem from the cerebrum is complex, both anatomically and taxonomically. Some taxonomies describe the brain stem as the pons, medulla and mesencephalon while others include diencephaletic regions.
The adult human brainstem emerges from parts of all three vesicles in the neural tube. The myelencephalon and metencephelon emerge from the rhombencephalon. The mesencephalon matures to become a vital link for nerve pathways related to movement. The prosencephalon gives rise to the diencephalon and to the telencephalon.