Extrapyramidal System

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extrapyramidal system

[¦ek·strə‚pir·ə′mid·əl ′sis·təm]
(neuroscience)
Descending tracts of nerve fibers arising in the cortex and subcortical motor areas of the brain.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Extrapyramidal System

 

a group of brain structures in the hemispheres and brainstem involved in the central control of movements without the participation of the corticospinal, or pyramidal, system.

From the standpoint of evolution the extrapyramidal system is the most ancient system of motor control. It consists of the basal ganglia, red and interstitial nuclei, tectum, substantia nigra, reticular formation of pons varolii and medulla oblongata, nuclei of the vestibular system, and cerebellum. Some structures of the extrapyramidal system do not proceed directly to the spinal motor centers. Others are connected by conducting pathways to the segmental levels of the spinal cord, where they serve as an essential switching station for impulses traveling from the brain to moto-neurons. The impulses that travel along the fibers of the extrapyramidal system can reach the motoneurons through direct mono-synaptic connections or by switching in the various interneurons of the spinal cord.

The extrapyramidal system plays an important role in the coordination of movements, locomotion, and maintenance of posture and muscle tone. It is closely associated with the control of truncal muscles and proximal portions of the limbs. It is also involved in emotional manifestations, for example, laughing and crying. Injury to the pyramidal system decreases muscle tone and impairs motor functions (causing, for example, hyperkinesia and parkinsonism).

REFERENCES

Kostiuk, P. G. Struktura i funktsiia niskhodiashchikh sistem spinnogo mozga. Leningrad, 1973.
Shapovalov, A. I. Neirony i sinapsy supraspinal’nykh motornykh sistem. Leningrad, 1975.

A. I. SHAPOVALOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Significant adverse effects like drowsiness, sedation, dizziness, headache or extrapyramidal effects were not observed in both the groups.
Trihexyphenidyl, which is an anticholinergic, was found to be frequently prescribed with olanzapine because it was used in managing the extrapyramidal effects associated with haloperidol.
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Abdominal pain is usually spasmodic due to disordered motility and metoclopramide should be considered if severe, although its extrapyramidal effects in young children warrant caution.
What was possibly more surprising was we did not see a significant change in extrapyramidal effects," Dr.
Todd et al., for example, found that SCH23390 (a selective antagonist of dopamine [D.sub.1] receptors) and haloperidol (an antagonist of dopamine [D.sub.2] receptors) reduced the volume of water consumed but increased chewing behavior, which led the authors to conclude that schedule-induced polydipsia could be a good model to evaluate neuroleptic drugs owing to its sensitivity to the extrapyramidal effects produced by these substances.

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