Extrapyramidal System

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extrapyramidal system

[¦ek·strə‚pir·ə′mid·əl ′sis·təm]
Descending tracts of nerve fibers arising in the cortex and subcortical motor areas of the brain.

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).


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


References in periodicals archive ?
Atypical antipsychotics have fewer extrapyramidal side effects because of a weak dopamine D2 receptor binding affinity or a strong antagonistic effect on serotonin 5-HT2a receptor (6).
Antipsychotic agents are usually first-line pharmacological therapies for delirium, but these agents are sometimes ineffective in this setting, and are associated with adverse events such as prolongation of the QT interval, and with extrapyramidal side effects such as akathisia, tremors, and, less frequently, the neuroleptic malignant syndrome, Dr.
Olanzapine, risperidone, and quetiapine are associated with a higher risk of weight gain, and aripiprazole and ziprasidone have been linked to a higher risk of extrapyramidal side effects.
This edition has updates to antipsychotic dosages; restructured information on antipsychotic-induced extrapyramidal side effects and their management; more on dosing recommendations for patients with renal or hepatic impairment; pharmacogenomics information for dementia drugs; new drugs and preparations, such as Forfivo, Gralise, Horizant, and Trokendi XR; more on vilazodone; the addition of synthetic cannabinoids to the drugs of abuse; updates on the psychotropic usage of natural health products; and patient handouts.
In my opinion, most of the SGAs, which included in order of appearance: Risperdal, Zyprexa, Seroquel, Geodon, Abilify, and Invega, reduced the risk of extrapyramidal side effects like tremors and stiffness.
Notably, there were no extrapyramidal side effects (EPS) and no cognitive impairment, side effects that are often observed following treatment with other antipsychotic drugs at high doses.
In addition to covering classes of psychiatric medications, the book also covers agents for treating extrapyramidal side effects, drugs of abuse, treatments for substance use disorders, new unapproved treatments for psychiatric disorders, and herbal and natural products.
Akinesia, and other extrapyramidal side effects of antipsychotics without tremors with accompanying low mood or dysphoria can also mimic depression, and termed as 'akinetic depression' (20).
Data from preclinical and Phase 1 studies demonstrated that the compound may retain the efficacy of currently available typical and atypical antipsychotic drugs while achieving a much higher safety profile as evidenced by a lack of metabolic or extrapyramidal side effects.
However, Didriksen and Christensen (1993) argued that the suppression of schedule-induced polydipsia by dopamine blockers is not due to the induction of extrapyramidal side effects, because that suppression was not antagonized by scopolamine (an anticholinergic drug used to counteract neuroleptic-induced dystonia) or by diazepam (a benzodiazepine used to counteract akathisia).
9) The dose threshold for extrapyramidal side effects was highly variable in the above studies, making a cut-off of appropriate metoclopramide dosing very difficult.
These drugs have a tendency to produce fewer extrapyramidal side effects while treating more of the negative symptoms of schizophrenia.

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