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Pyramidal and extrapyramidal tracts
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These motor signals are carried through two tracts, the pyramidal and extrapyramidal tracts.
Neurons in the extrapyramidal tract do not directly innervate lower motor neurons, but instead help coordinate muscle movement by indirectly activating or inhibiting groups of lower motor neurons through interneurons.
The pyramidal pathway is the primary pathway that carries out motor commands for voluntary movement. And it can be broken down into two main tracts, the corticospinal tract and the corticobulbar tract.
At the level of the medulla, these fibers divide, and 90% of them form the lateral corticospinal tract which cross over to the opposite side of the medulla at the pyramidal decussation, while the remaining 10% of them form the anterior corticospinal tract which does not cross over just yet, and both tracts then travel through the spinal cord.
Pyramidal tracts are long nerve pathways in the brain that transmit signals from the cerebral cortex to the spinal cord, through the medullary pyramids. They control the voluntary motor function of the body and face. Neurons in the pyramidal tract are composed of upper motor neurons that directly innervate lower motor neurons in the anterior horn of the spinal cord. In contrast to the pyramidal tracts, the extrapyramidal tracts do not start in the cerebral cortex. Instead, their upper motor neurons are located within nuclei in the brain stem and they send their axons down the spinal cord and are involved in the control of movement and coordination.
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