Extrapyramidal system

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Extrapyramidal system
Spinal cord tracts - English.svg
Medulla spinalis. (Extrapyramidal tracts are labeled as a group in red, at bottom left.)
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Latin systema extrapyramidale
NeuroNames 2070
Anatomical terms of neuroanatomy

In anatomy, the extrapyramidal system is a part of the motor system network causing involuntary actions. [1] The system is called extrapyramidal to distinguish it from the tracts of the motor cortex that reach their targets by traveling through the pyramids of the medulla. The pyramidal tracts (corticospinal tract and corticobulbar tracts) may directly innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn cells or certain cranial nerve nuclei), whereas the extrapyramidal system centers on the modulation and regulation (indirect control) of anterior (ventral) horn cells.

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Extrapyramidal tracts

The extrapyramidal tracts are chiefly found in the reticular formation of the pons and medulla, and target lower motor neurons in the spinal cord that are involved in reflexes, locomotion, complex movements, and postural control. These tracts are in turn modulated by various parts of the central nervous system, including the nigrostriatal pathway, the basal ganglia, the cerebellum, the vestibular nuclei, and different sensory areas of the cerebral cortex. All of these regulatory components can be considered part of the extrapyramidal system, in that they modulate motor activity without directly innervating motor neurons.

The extrapyramidal tracts include parts of the following: [2] [3]

See also

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<span class="mw-page-title-main">Pyramidal tracts</span> The corticobulbar tract and the corticospinal tract

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<span class="mw-page-title-main">Rubrospinal tract</span> Part of the nervous system

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<span class="mw-page-title-main">Fastigial nucleus</span> Grey matter nucleus in the cerebellum

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<span class="mw-page-title-main">Cranial nerve nucleus</span>

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<span class="mw-page-title-main">Vestibulospinal tract</span> Neural tract in the central nervous system

The vestibulospinal tract is a neural tract in the central nervous system. Specifically, it is a component of the extrapyramidal system and is classified as a component of the medial pathway. Like other descending motor pathways, the vestibulospinal fibers of the tract relay information from nuclei to motor neurons. The vestibular nuclei receive information through the vestibulocochlear nerve about changes in the orientation of the head. The nuclei relay motor commands through the vestibulospinal tract. The function of these motor commands is to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.

<span class="mw-page-title-main">Alpha motor neuron</span> Large lower motor neurons of the brainstem and spinal cord

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<span class="mw-page-title-main">Medial vestibulospinal tract</span>

The medial vestibulospinal tract is one of the descending spinal tracts of the ventromedial funiculus of the spinal cord. It is found only in the cervical spine and above.

<span class="mw-page-title-main">Spinal cord</span> Long, tubular central nervous system structure in the vertebral column

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<span class="mw-page-title-main">Blocq's disease</span> Loss of memory of specialized movements causing the inability to maintain an upright posture

Blocq's disease was first considered by Paul Blocq (1860–1896), who described this phenomenon as the loss of memory of specialized movements causing the inability to maintain an upright posture, despite normal function of the legs in the bed. The patient is able to stand up, but as soon as the feet are on the ground, the patient cannot hold himself upright nor walk; however when lying down, the subject conserved the integrity of muscular force and the precision of movements of the lower limbs. The motivation of this study came when a fellow student Georges Marinesco (1864) and Paul published a case of parkinsonian tremor (1893) due to a tumor located in the substantia nigra.

References

  1. Yuan, Rui; Di, Xin; Taylor, Paul A.; Gohel, Suril; Tsai, Yuan-Hsiung; Biswal, Bharat B. (30 April 2015). "Functional topography of the thalamocortical system in human". Brain Structure and Function. 221 (4): 1971–1984. doi:10.1007/s00429-015-1018-7. PMC   6363530 . PMID   25924563.
  2. Costanzo, Linda S. (30 July 2010). Physiology. LWW. ISBN   978-0781798761.
  3. Creative Commons by small.svg  This article incorporates text available under the CC BY 4.0 license.Betts, J Gordon; Desaix, Peter; Johnson, Eddie; Johnson, Jody E; Korol, Oksana; Kruse, Dean; Poe, Brandon; Wise, James; Womble, Mark D; Young, Kelly A (July 22, 2023). Anatomy & Physiology. Houston: OpenStax CNX. 14.3 Motor responses. ISBN   978-1-947172-04-3.