What Is the Corticospinal Tract?

The corticospinal system is the largest descending nerve fiber bundle in the human spinal cord. Its neurons are in the central anterior gyrus motor area of the cerebral cortex, and other areas of the cortex. Its fibers are gathered into a bundle at the hind foot of the ipsilateral inner capsule, descending to the bulbus to form a cone, and most of the lower end of the cone crosses to the contralateral side, forming the cortex Lateral spinal cord, which descends from the lateral cord of the spinal cord, and stops directly or indirectly at motor neurons in the anterior horn; a small portion of fibers that are not crossed in the pyramid form the cortical spinal cord anterior bundle, which also descends directly or indirectly from the anterior cord of the spinal cord. Anterior horn cells. The function of this bundle is to govern the voluntary movement of skeletal muscle, which together with the anterior horn motor neurons form a conductive pathway of voluntary movement.

The corticospinal system is the largest descending nerve fiber bundle in the human spinal cord. Its neurons are in the central anterior gyrus motor area of the cerebral cortex, and other areas of the cortex. Its fibers are gathered into a bundle at the hind foot of the ipsilateral inner capsule, descending to the bulbus to form a cone, and most of the lower end of the cone crosses to the contralateral side, forming the cortex Lateral spinal cord, which descends from the lateral cord of the spinal cord, and stops directly or indirectly at motor neurons in the anterior horn; a small portion of fibers that are not crossed in the pyramid form the cortical spinal cord anterior bundle, which also descends directly or indirectly from the anterior cord of the spinal cord. Anterior horn cells. The function of this bundle is to govern the voluntary movement of skeletal muscle, which together with the anterior horn motor neurons form a conductive pathway of voluntary movement.

Chinese name

Corticospinal tract

Location

Lower end of cone

Features

Cross each other

Category

biological

Injury treatment

Limb paralysis

Histological characteristics of the corticospinal tract

Cortical spinal cord staining method: Take the brain (medulla oblongata) and spinal cord neck, chest, waist, and sacral sections for frozen cross-sections. After sectioning with Luxol FastBlue staining, gray matter can be seen in the medulla oblongata and spinal cord. Blue, clear state, the bulbar cone is stained with dark blue, which is clearly distinguished from the surrounding structure. Then the dark blue positive fibers labeled with Luxol FastBlue in the cone cross the dorsal side after crossing the cone to the gray matter of the spinal cord. The ventral side of the cord descends deep, and in the spinal cord neck, chest, and lumbar posterior cords, the dark blue Luxol FastBlue-positive fibers have a clear border, and gradually disappear after the spinal cord segment.

Luxol FastBlue (LFB) is a copper-phthalocyanine dye with dyeing properties. If it is counterstained by neutral red or tar violet, it can still show the nucleus and Nissl bodies of neurons. Myelin staining has a certain strengthening effect. LuxolFastBlue stains the myelin sheath with a bright color and a certain specificity. It is a better specific marker for identifying nerve myelin sheaths and can be used to display nerve conduction bundles rich in myelin sheaths, such as cortical spinal cord bundles. The corticospinal tract is composed of most of myelinated fibers and part of myelinated fibers. Myelin is an important component of myelinated nerve fibers. 30% of its dry weight is protein and 70% is lipidoid. Proteolipid or lipoprotein. Protein lipids are easily soluble in organic solvents and will be lost during the tissue preparation process without special treatment.

Three anatomical features of the corticospinal tract

It is not yet possible to determine the position of all the starting cells in the human corticospinal tract. The corticospinal tract completely crosses to the contralateral side in the medulla oblongata, and descends along the ventral side of the posterior cord, reaching the lumbar energy segment of the spinal cord. Most of them are the lateral cortical spinal cord bundle, which runs on the dorsal side of the lateral cord, and descends to reach the energy node; the uncrossed cortical spinal cord anterior bundle, which travels on the anterior cord only reaches the upper thoracic spinal cord; the uncrossed cortical spinal cord, Walk on the ventral side of the lateral cord. The corticospinal tracts of rats are distributed in the posterior horn base and central zone within the gray matter of the spinal cord. The monkey's cortical spinal tracts originate from the corticospinal tract fibers of the central anterior gyrus into the central zone and the anterior and posterior horn base gray matter; The fibers mainly stop at the posterior horn, especially the natural nucleus of the posterior horn. Cats show that the corticospinal tract can end in the thin nucleus, wedge nucleus, and gray matter in the posterior and central horns of the spinal cord. No such terminal is found in the anterior horn.

The direct effect of the corticospinal tract on motor neurons is also very small, mainly controlling the motor neurons that govern the distal muscles of the limbs. The cortical spinal cord exercises indirect control over most motor neurons. They can reach motor neurons through other descending systems. For example, the red nucleus has single and double synapses with the cortical spinal cord. The corticospinal tract can also affect intermediate neurons that mediate spinal cord reflexes or affect the spinal cord reflexes through the sensory afferent system.