====== Spinal cord tracts ======

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===== Descending (Motor) Tracts =====

^ No. ^ Pathway                             ^ Function                          ^ Side of Body ^ Notes ^
| 1   | [[Anterior corticospinal tract]]        | Skilled movement                  | Opposite *   | Fibers cross at the anterior white commissure to synapse on alpha motor neurons or interneurons. Some fibers remain ipsilateral. Identifiable only in cervical and upper thoracic levels. |
| 2   | [[Medial longitudinal fasciculus]]      | ?                                  | Same         | Likely involved in coordination of head, neck, and eye movements. No primary motor output defined. |
| 3   | [[Vestibulospinal tract]]               | Facilitates extensor muscle tone  | Same         | Critical for posture and balance; acts on axial and extensor muscles. |
| 4   | Medullary (ventrolateral) [[reticulospinal tract]] | Automatic respiration?        | Same         | Involved in muscle tone and automatic movements; may contribute to respiratory rhythm. |
| 5   | [[Rubrospinal tract]]                   | Facilitates flexor muscle tone    | Same         | Minimal role in humans; more relevant in quadrupeds. May support fine motor adjustment. |
| 6   | Lateral corticospinal ([[pyramidal]]) [[tract]] | Skilled voluntary movement     | Same         | Primary motor tract; decussates at pyramids in medulla. Controls fine distal movements. |

*The terminal fibers of this uncrossed tract usually cross in the anterior white commissure to synapse on alpha motor neurons or on internuncial neurons. A minority of the fibers do remain ipsilateral. Also, an anterior corticospinal tract is easily identified only in the cervical and upper thoracic regions.


see the [[intermediolateral gray nucleus]] is only present from T1 to≈ L1 or L2 where
there are sympathetic [thoracolumbar outflow] nuclei). It is schematically divided into ascending
and descending halves; however, in actuality, ascending and descending paths coexist on both sides.
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The figure also depicts some of the laminae according to the scheme of Rexed. Lamina II is equiv-
alent to the substantia gelatinosa. Laminae III and IV are the nucleus proprius. Lamina VI is located in
the base of the posterior horn.