Tracts of spinal cord in lateral white column

Ascending tracts

1. Lateral spino thalamic tract:
   • It lies medial to the preceding. The fibres arise from the dorsal horn of the opposite side cross the median plane and ascend through the medulla.
   • It ascends as the spinal lemniscus and reaches the ventral portion of the lateral nucleus of the thalamus from where they are relayed to cerebral cortex.
   • The tract conveys impulses of pain and temperature.
2. Dorsal spino-cerebellar tract:
   • This is situated at the periphery of the lateral column. Medially, it is in contact with the crossed pyramidal tract.
   • It begins about the second or third lumbar segment and passes into the cerebellum through the restiform body.
   • Its fibres arise from the nucleus dorsalis of the same side.
3. Ventral spino-cerebellar tract:
   • It is a crescentic, flattened band that is situated at the periphery of the lateral white column below the preceding.
   • The fibres arise from the nucleus dorsalis and adjoining dorsal horn of the same and opposite sides.
   • The tract extends from the upper lumbar region to the upper part of the pons, then into the anterior cerebellar peduncle to reach the cerebellum.
   • These tracts carry the impulses of the proprioceptive sensibility from the locomotor apparatus to cerebellum, essential for adjustments of muscle tonus and synergic control during the performance of the voluntary movements.
4. Spino-tectal tract:
   • It is placed medial to the ventral spino-cerebellar tract and the lateral spino-thalamic tract.
   • The fibres arise from the dorsal horn of the opposite side, cross the median plane; ascend to the mid brain where they terminate in the anterior quadrigeminal body.
   •  This is an afferent pathway for spino-visual reflexes, resulting in movements of eye toward the source of stimulation.

Descending tracts

1. Cortico-spinal or Crossed pyramidal tract:
   • It is a motor tract in the lateral white column.
   • Its fibres are the axons of the pyramidal cells of the motor area of the cerebral cortex of the opposite side.
   • The fibres descend through the internal capsule and crura cerebri enter the medulla oblongata, decussate and appear on the inferior face of the medulla as inferior pyramids.
   • They descend into the lateral column and end by synapses around the motor cells of the ventral horn. This is the motor pathway that controls all voluntary actions involving skeletal muscles.

• Rubro-spinal tract:
  • This is ventral to the preceding and appears as a triangular area on section.
  • Its fibres arise from the red nucleus of the midbrain and descend in the lateral column to end around the motor cells of the ventral horn of the cord.
  • Through this tract the ventral horn cells are brought under the control of cerebellum and corpus fstriatum.
  • The former exercises synergic control while the latter controls the automatic associated movements.
• Tecto-spinal tract:
  • This is ventral to the preceding.
  • The fibers arise from the tectum or upper part of midbrain consisting of anterior and posterior colliculi and immediately decussate (in the midbrain) descends in the lateral white column of spinal cord to end in the ventral horn cells of the spinal cord.
  • This serves as an efferent pathway for visuospinal and auditospinal reflexes.