Brain stem

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Brain: Brain stem
Image:Gray682.png
Superficial dissection of brain-stem. Lateral view.
Latin	truncus encephali
Gray's	subject #187
NeuroNames	ancil-218
MeSH	A08.186.211.132

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. (See also nervous system)

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.

[edit] Function

The brain stem is the stalk of the brain below the cerebral hemispheres. It is the major route for communication among 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.

[edit] See also

Cranial nerve nucleus

[edit] References

Anthoney, Terence (1994). Neuroanatomy and the Neurologic Exam: A Thesaurus of Synonyms, Similar-Sounding Non-Synonyms, and Terms of Variable Meaning. Boca Raton, Florida: CRC-Press. ISBN 0-8493-8631-4.