Brain stem
The brain stem is the 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 oblongata, 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.
Encyclopedia
The
brain stem is the 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 oblongata, 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.
The lower part of the brain stem is the medulla oblongata, grossly comprising the
medullary pyramids and the olivary bodies or
olives. The pons is a structure above the medulla. The reticular activating system is situated in between the medulla and metencephalon, and is considered to be at the "core."
Differentiation of the brain stem from the
cerebrum is complex, both anatomically and taxonomically. Some taxonomies describe the brain stem as the medulla and mesencephalon while others include diencephalic regions.
The adult human brainstem emerges from parts of all three vesicles in the neural tube.
Function
The brain stem is the stalk of the
brain below the
cerebral hemispheres. It is the major route for communication between the forebrain, the
spinal cord, and peripheral nerves. It controls various
autonomic functions such as respiration and the regulation of
heart rhythms as well as
perceptual functions such as the primary aspects of sound localization.
Afferent stimulus from the body passes from the spinal cord, through the pons, which routes the stimulus to the opposite side of the brain for processing. So, if a person suffers a right-side brain stroke, the left side of the body is normally impacted due to the cross-over of information in the pons.
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