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| Precentral gyrus | |
|---|---|
 Precentral gyrus a prominent gyrus of thefrontal lobe | |
| Details | |
| Identifiers | |
| Latin | gyrus precentralis |
| TA98 | A14.1.09.119 |
| TA2 | 5458 |
| FMA | 61894 |
| Anatomical terms of neuroanatomy | |
Theprecentral gyrus is a prominentgyrus on the surface of the posteriorfrontal lobe of thebrain. It is the site of theprimary motor cortex that in humans iscytoarchitecturally defined asBrodmann area 4.
The precentral gyrus lies in front of thepostcentral gyrus - mostly on the lateral (convex) side of eachcerebral hemisphere - from which it is separated by thecentral sulcus.Itsanterior border is represented by theprecentral sulcus, whileinferiorly it borders to thelateral sulcus (Sylvian fissure).Medially, it is contiguous with theparacentral lobule.
Theinternal pyramidal layer (layer V) of the precentralcortex contains giant (70-100 micrometers)pyramidal neurons calledBetz cells, which send longaxons to the contralateral motor nuclei of thecranial nerves and to thelower motor neurons in the ventral horn of thespinal cord. These axons form thecorticospinal tract. The Betz cells along with their long axons are referred to asupper motor neurons (UMN).
There is a precise somatotopic representation of the different body parts in the primary motor cortex, with the leg area located medially (close to the midline), and the head and face area located laterally on the convex side of the cerebral hemisphere (cortical homunculus). The arm and hand motor area is the largest and occupies the part of precentral gyrus, located inbetween the leg and face area.
The precentral gyrus is specialised for sending signals down to the spinal cord for movement.[1] As they travel down through the cerebralwhite matter, the motor axons move closer together and form part of theposterior limb of theinternal capsule. They continue down into thebrainstem, where some of them, after crossing over to the contralateral side, distribute to the cranial nerve motor nuclei. (Note: a few motor fiberssynapse with lower motor neurons on the same side of the brainstem). After crossing over to the contralateral side in themedulla oblongata (pyramidal decussation), the axons travel down the spinal cord as thelateral corticospinal tract. Fibers that do not cross over in the brainstem travel down the separateventral corticospinal tract and most of them cross over to the contralateral side in the spinal cord, shortly before reaching the lower motor neurons.
Branches of themiddle cerebral artery provide most of the arterial blood supply for theprimary motor cortex. The medial aspect (leg areas) is supplied by branches of theanterior cerebral artery.
Lesions of the precentral gyrus result inparalysis of the contralateral side of the body (facial palsy, arm-/legmonoparesis,hemiparesis) - seeupper motor neuron. New research has identified this as the part of the brain that makes sure our words are being properly articulated. This knowledge could help treatspeech disorders and neural disorders in the future, the researchers say.[2]
This article incorporatestext available under theCC 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 6, 2023).Anatomy & Physiology. Houston: OpenStax CNX. 12.3 The function of nervous tissue.ISBN 978-1-947172-04-3.