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Descending motor tracts

The tracts that carry movement commands down the cord. The corticospinal tract for voluntary movement, and the extrapyramidal tracts from the brainstem for posture, balance, tone and corrections.

Updated 2026-10-023 sources

Depth:

Why it matters

Every movement of the trunk and limbs is carried out by lower motor neurons in the ventral horn of the cord ^[1]. The descending tracts are how the brain tells them what to do: the corticospinal tract for voluntary commands, and the extrapyramidal system for the rest ^[1].

What it is

Voluntary commands travel from upper motor neurons in the primary motor cortex to lower motor neurons in the ventral horn ^[1]. Other descending connections between the brain and the cord are called the extrapyramidal system ^[1]:

The tectospinal tract runs from the midbrain to the cord and matters for postural movements driven by the superior colliculus, also called the tectum ^[1].
The reticulospinal tract connects the reticular system of the brainstem with the cord; it influences trunk and proximal limb muscles for posture and locomotion, contributes to muscle tone and influences autonomic functions ^[1].
The vestibulospinal tract connects the vestibular nuclei with the cord, so that posture, movement and balance can be adjusted using equilibrium information ^[1].
The rubrospinal tract carries corrective commands from the red nucleus of the midbrain ^[1].

How it works

Corrections come through the cerebellum: conflicts between the commands sent by the cerebrum and the body-position information from proprioceptors make the cerebellum stimulate the red nucleus, which sends corrective commands down the rubrospinal tract ^[1].

The extrapyramidal pathways are influenced by structures below the cortex. The basal nuclei, which help regulate movement started by the central nervous system, influence the extrapyramidal system and its feedback through the thalamus to the motor cortex ^[1].

Lower motor neurons that drive the axial muscles of the trunk lie in the medial ventral horn ^[1]. In this site's cross-sections the descending tract outlines come from the PAM50 white-matter atlas ^{[2, 3]}.

Excitatory synapse (filled arrowhead)
Inhibitory synapse (bar)
Modulatory (open circle)
Signal or data flow, not a synapse (dashed)
Midline crossing (decussation)

Figure 1. Lateral corticospinal tract. Upper motor neurons in the left motor cortex send axons down through the internal capsule, cerebral peduncle and pons; most cross at the pyramidal decussation and descend in the right lateral cord to the lower motor neurons of right-sided limb muscles.^[1] Schematic

The neuromuscular junction is strictly excitatory, so the muscle contracts when its motor neuron fires.^[1]
The anterior corticospinal tract (not drawn) controls the muscles of the trunk and is not entirely contralateral.^[1]

Simplified: One upper and one lower motor neuron stand for many; the synapse in the ventral horn is drawn as the end of the tract, without claiming its sign.

Text description of this diagram

Upper motor neurons in the left motor cortex send axons down through the internal capsule, cerebral peduncle and pons; most cross at the pyramidal decussation and descend in the right lateral cord to the lower motor neurons of right-sided limb muscles.
Primary motor cortex (left side, Cerebral cortex) to Internal capsule (left side, Deep brain); signal or data flow (not a synapse).
Internal capsule (left side, Deep brain) to Cerebral peduncle (left side, Midbrain); signal or data flow (not a synapse).
Cerebral peduncle (left side, Midbrain) to Pons (left side, Pons); signal or data flow (not a synapse).
Pons (left side, Pons) to Pyramid (left side, Medulla); signal or data flow (not a synapse).
Pyramid (left side, Medulla) to Lateral corticospinal (right side, Spinal cord); signal or data flow (not a synapse); crosses the midline at the pyramidal decussation.
Lateral corticospinal (right side, Spinal cord) to Lower motor neuron (right side, Ventral horn); signal or data flow (not a synapse); synapse in the ventral horn.
Lower motor neuron (right side, Ventral horn) to Limb muscle (right side, Muscle); excitatory synapse; neuromuscular junction.

When it does not behave

When the cerebellum does not work properly, coordination and balance are severely affected, because the corrections it sends through the rubrospinal tract are lost ^[1].

Common misconceptions

Misconception: All movement commands come from the motor cortex.

Brainstem tracts such as the reticulospinal and vestibulospinal tracts control posture, tone and balance, and the rubrospinal tract carries corrections ^[1].

Check yourself

Which tract adjusts posture using information from the inner ear's balance organs?

The vestibulospinal tract, from the vestibular nuclei ^[1].

How does the cerebellum send corrections to the cord?

Through the red nucleus and the rubrospinal tract ^[1].

References

Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 14.3 Motor Responses. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/14-3-motor-responses
Lévy S, Benhamou M, Naaman C, Rainville P, Callot V, Cohen-Adad J. White matter atlas of the human spinal cord with estimation of partial volume effect. NeuroImage. 2015;119:262-271. doi:10.1016/j.neuroimage.2015.06.040
De Leener B, Fonov VS, Collins DL, Callot V, Stikov N, Cohen-Adad J. PAM50: Unbiased multimodal template of the brainstem and spinal cord aligned with the ICBM152 space. NeuroImage. 2018;165:170-179. doi:10.1016/j.neuroimage.2017.10.041

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