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 It might be outdated or ideologically biased.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.
References in periodicals archive ?
There is some evidence justifying the introduction of olanzapine and risperidone as well, but more pronounced extrapyramidal side effects can be expected, in comparison with quetiapine.
Typical antipsychotics (eg; Haloperidol) are the drugs which have high affinity for dopamine D2 receptors and have high propensity to cause extrapyramidal side effects and raise prolactin levels.
An "atypical" label is used to distinguish antipsychotic drugs that are less likely to cause extrapyramidal side effects compared to "typical" antipsychotic drugs.
Being the first SGA (no acute extrapyramidal side effects at all, in contrast to all FGAs), it became the "mechanistic model" for all other SGA agents, which were introduced starting in 1993.
Compared to dopamine receptor antagonists, clozapine produces fewer extrapyramidal side effects, such as dystonia, parkinsonism and akinezia (3, 8).
He had joint limitations in the shoulders, elbows, and hands, with extrapyramidal side effects and pyramidal hypertonia of the upper limbs.
He was commenced on risperidone and dose increased to 2mg twice daily at which point he developed extrapyramidal side effects. As his symptoms persisted beyond one week and there was a positive family history, a diagnosis of bipolar affective disorder, currently manic episode without psychotic symptoms, was made.
Atypical antipsychotics such as olanzapine are more frequently prescribed because they are less likely to cause extrapyramidal side effects as compared with the typical antipsychotics such as haloperidol [51, 52].
(5) Ondansetron has been reported to cause extrapyramidal side effects in a considerable number of cases.
Systematic screening for anti-NMDAR encephalitis should also be considered in women with severe acute psychosis during the postpartum period, particularly in the setting of extrapyramidal side effects of antipsychotic agents.
This receptor occupancy profile with relatively higher affinity for the 5HT2A receptor compared with the D2 receptor is in part responsible for the antipsychotic characteristics and low incidence of extrapyramidal side effects of quetiapine.
In addition to the previously mentioned sedation and orthostasis, typical antipsychotics are much more likely to cause elevated prolactin levels and extrapyramidal side effects.

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