Anatomy of Spinal Cord Tracts

General Overview

• Spinal cord tracts divided into:
  • Ascending tracts (sensory)
  • Descending tracts (motor)
• Tracts make up white matter (due to myelin)
• Gray matter located centrally (ventral and dorsal horns)

Ascending Pathways

• Transport sensory information from the body
• Colored blue in diagrams

Dorsal (Posterior) Column

• Fasciculus Cuneatus
  • Fine touch, tactile sensation, vibration, proprioception
  • Signals from upper limb (T6 and above)
• Fasciculus Gracilis
  • Fine touch, tactile sensation, vibration, proprioception
  • Signals from lower limb (generally below T6)
  • Mnemonic: 'L' in gracilis reminds of lower limbs
• Function: Run ipsilaterally and decussate in medulla
  • Spinal cord injury leads to ipsilateral loss of fine touch, vibration, proprioception

Anterolateral Pathways

• Anterior Spinothalamic Tract
  • Crude touch and pressure
• Lateral Spinothalamic Tract
  • Pain and temperature
• Function: Decussate within spinal cord then travel to brain
  • Lesion causes contralateral loss of sensation
  • Note: Nerves may ascend 1-2 vertebral levels before decussating

Unconscious Sensation Pathways

• Anterior and Posterior Spinocerebellar Tracts & Spino-olivary Tract
  • Transmit proprioceptive information of lower limbs to cerebellum
• Cuneocerebellar and Rostral Spinocerebellar Tracts
  • Transmit proprioceptive information of upper limbs and neck to cerebellum

Descending Pathways

• Responsible for muscle movement
• Colored red in diagrams

Pyramidal Tracts

• Anterior and Lateral Corticospinal Tracts
  • Involved with voluntary movement of the limbs
  • Lateral Corticospinal Tract
    • Decussated fibers (originating from one hemisphere, traveling contralaterally)
  • Anterior Corticospinal Tract
    • Decussate at the level they innervate

Extrapyramidal Tracts

• Rubrospinal Tract
  • Provides contralateral innervation, fine motor control
• Reticulospinal Tracts
  • Medial Reticulospinal Tract: Facilitates voluntary contraction; increases muscle tone
  • Lateral Reticulospinal Tract: Inhibits voluntary movement; reduces muscle tone; role in automatic breathing
• Vestibulospinal Tract
  • Controls balance and posture
• Tectospinal Tract
  • Coordinates head movements with vision