Pyramidal tracts

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The pyramidal tract is a descending white matter tract of the central nervous system that provides voluntary control of striated muscle movement. It is composed of two distinct tracts:

• Corticospinal tract, which mainly arises from the primary motor cortex in the brain. It receives additional contributions from the premotor, supplementary motor and the somatosensory cortex. This tract carries motor signals from upper motor neurons (UMN) of the cerebral cortex to the lower motor neurons (LMN) of the spinal cord, which further relay them to the muscles of the trunk and limbs.
• Corticonuclear (corticobulbar) tract, which also arises from upper motor neurons (UMN) in the primary motor cortex in the brain. Unlike the corticospinal tract, the lower motor neurons (LMN) of the corticonuclear tract are found in the motor cranial nerve nuclei of the brainstem, which innervate the muscles of the head, face and neck.

It’s important to note that according to the Terminologia Anatomica (TA), the term ‘pyramidal tract’ refers only to the corticospinal tract, while the corticonuclear tract is regarded as a separate entity. However, most of the literature uses it as an umbrella term for both the corticospinal and corticonuclear tracts.

Learn more about the pyramidal tract by watching the video below!

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Summary