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Encyclopedia > Precentral gyrus

The precentral gyrus (a.k.a. motor strip) is a prominent structure on the surface of the posterior frontal lobe. It is the site of the primary motor cortex (Brodmann area 4). The frontal lobe is an area in the brains of vertebrates. ... Early work on motor cortex function Back in the 1940s, Canadian neurosurgeon Wilder Penfield wanted to know which bits of epileptics brains he could suck out without them noticing. ...


Precentral Gyrus

The precentral gyrus lies in front of the postcentral gyrus - mostly on the lateral (convex) side of the cerebral hemispheres - from which it is sepparated by the central sulcus. Its anterior border is represented by the precentral sulcus, while inferiorly it borders to the lateral fissure (Sylvian fissure). Medially, it is contiguos with the paracentral lobule. The postcentral gyrus is a prominent structure in the parietal lobe of the human brain and an important landmark. ... Á cerebrum is a part of the brain. ... Central sulcus of the human brain. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Precentral sulcus of the human brain. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Lateral sulcus The lateral sulcus (also called Sylvian fissure or lateral fissure) is one of the most prominent structures of the human brain. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ...


The internal pyramidal layer (layer V) of the precentral cortex contains giant (70-100 micrometers) pyramidal neurons (a.k.a. Betz cells), which send long axons to the contralateral motor nuclei of the cranial nerves and to the lower motor neurons in the ventral horn of the spinal cord. These axons form the corticospinal tract. The Betz cells' along with their long axons are referred to as the upper motor neuron (UMN). Location of the Cerebral cortex Slice of the Cerebral cortex, ca. ... Neurons (also spelled neurones or called nerve cells) are the primary cells of the nervous system. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... Motor neurons are classified as either upper motor neurons or lower motor neurons. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain, and the spinal cord. ... Motor neurons are classified as either upper motor neurons or lower motor neurons. ...


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 (motor homunculus). The arm and hand motor area is the largest and occupies the part of precentral gyrus, located inbetween the leg and face area. Hartsoekers homunculus The concept of a homunculus (Latin for little man, sometimes spelled homonculus) is often used to illustrate the functioning of a system. ...


As they travel down through the cerebral white matter, the motor axons move closer together and form part of the posterior limb of the internal capsule. They continue down into the brainstem, where some of them, after crossing over to the contralateral side, distribute to the cranial nerve motor nuclei. (Note: a few motor fibers synapse with lower motor neurons on the same side of the brainstem). After crossing over to the contralateral side in the medulla oblongata (pyramidal decussation), the axons travel down the spinal cord as the lateral corticospinal tract. Fibers that do not cross over in the brainstem travel down the separate ventral corticospinal tract and most of them cross over to the contralateral side in the spinal cord, shortly before reaching the lower motor neurons. White matter is one of two categories of tissue in the nervous system. ... An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, which conducts electrical impulses away from the neurons cell body or soma. ... The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... Synapses allow nerve cells to communicate with one another through axons and dendrites, converting electrical signals into chemical ones. ... Motor neurons are classified as either upper motor neurons or lower motor neurons. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The medulla oblongata is the lower portion of the brainstem. ... The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain, and the spinal cord. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain, and the spinal cord. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain, and the spinal cord. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... Motor neurons are classified as either upper motor neurons or lower motor neurons. ...


Branches of the middle cerebral artery provide most of the arterial blood supply for the primary motor cortex. The medial aspect (leg areas) is supplied by branches of the anterior cerebral artery. Early work on motor cortex function Back in the 1940s, Canadian neurosurgeon Wilder Penfield wanted to know which bits of epileptics brains he could suck out without them noticing. ...


Lesions of the precentral gyrus result in paralysis of the contralateral side of the body (facial palsy, arm-/leg monoparesis, hemiparesis) - see upper motor neuron. Paralysis is the complete loss of muscle function for one or more muscle groups. ... Hemiparesis is the paralysis of one side of the body. ... Motor neurons are classified as either upper motor neurons or lower motor neurons. ...


See also


 
 

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