Corticospinal tract

The corticospinal tract is a descending pathway from the cerebral cortex to spinal circuits. It supports voluntary movement, especially precise control of the limbs and fingers.

Primary motor cortex: The frontal-lobe cortical region that contributes strongly to voluntary movement control. Many corticospinal axons originate in this cortical region.
Cerebral cortex: The folded outer layer of the cerebral hemispheres, involved in perception, cognition, and voluntary action. The tract begins in cortical regions, including motor and premotor areas.
Upper motor neuron: A motor-control neuron whose cell body lies in the brain and whose axon influences lower motor neurons. Corticospinal neurons are a major upper-motor-neuron system.
Rubrospinal tract: A descending motor pathway from the red nucleus to the spinal cord, prominent in many nonhuman mammals. It provides a brainstem route for limb control distinct from the corticospinal pathway.
Pyramidal decussation: The crossing of most corticospinal fibers at the junction of the medulla and spinal cord. This crossing makes each cerebral hemisphere mainly control the opposite side of the body.
Internal capsule: A compact bundle of white-matter fibers connecting the cerebral cortex with lower brain regions. Corticospinal fibers pass through its posterior limb on their descent.
Babinski sign: An upward great-toe response to sole stimulation in adults, associated with corticospinal-system dysfunction. An abnormal response can indicate disruption of descending motor pathways.
Reticulospinal tract: Descending fibers from the reticular formation that influence posture, locomotion, and muscle tone. It contributes more broadly to posture and movement than precise corticospinal control.
Lateral corticospinal tract: The crossed, lateral portion of the corticospinal tract in the spinal cord. It carries most corticospinal fibers and contributes to skilled distal limb movement.
Cerebral peduncle: A large bundle of nerve fibers on the front of the midbrain connecting cortex with lower centers. The descending tract traverses the cerebral peduncle before reaching the pons.

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