brain stem

brain stem lower part of the brain , adjoining and structurally continuous with the spinal cord. The upper segment of the human brain stem, the pons, contains nerve fibers that connect the two halves of the cerebellum . It is vital in coordinating movements involving right and left sides of the body. Below the pons and continuous with the spinal cord is the medulla, which transmits ascending and descending nerve fibers between the spinal cord and the brain. The medulla also directly controls many involuntary muscular and glandular activities, including breathing, heart contraction, artery dilation, salivation, vomiting, and probably laughing. The nuclei of some of the nerves that originate in the brain are also located in the brain stem. Nerve fibers in the brain stem do not readily regenerate, hence injury may result in permanent loss of function. See also nervous system .

brain stem The part of the brain which still conforms with the organization of the spinal cord. The brain stem is divided into four regions anterior to posterior: diencephalon, mesencephalon, metencephalon, and myelencephalon.

brain stem Stalk-like portion of the brain in vertebrates that includes everything except the cerebellum and the cerebral hemispheres. It provides a channel for all signals passing between the spinal cord and the higher parts of the brain. It also controls automatic functions such as breathing and heartbeat, digestion, and respiration.