Spinal Cord Tracts

Overview

• Spinal cord tracts are divided into ascending and descending tracts.
• Tracts comprise the white matter (due to myelin around axons), while gray matter is located centrally (comprising ventral and dorsal horns).

Ascending Pathways (Sensory Tracts)

• Function: Transport sensory information from the body.
• Color Code: Blue

Dorsal Column/Posterior Column

• Components: Fasciculus cuneatus and fasciculus gracilis.
  • Fasciculus cuneatus: Responsible for upper limb signals (T6 and above).
  • Fasciculus gracilis: Responsible for lower limb signals (below T6).
  • Function: Fine touch, vibration, proprioception.
  • Pathway: Ipsilateral through spinal cord, decussate in the medulla.
  • Lesion Impact: Loss of ipsilateral fine touch, vibration, proprioceptive sensation.

Anterolateral System

• Includes anterior and lateral spinothalamic pathways.
  • Anterior Spinothalamic Tract: Crude touch and pressure.
  • Lateral Spinothalamic Tract: Pain and temperature.
  • Pathway: Decussate within the spinal cord, then ascend.
  • Lesion Impact: Contralateral loss of crude touch, pressure, pain, and temperature (with exceptions as nerves may ascend one or two levels before crossing).

Unconscious Sensation Tracts

• Anterior and Posterior Spinal Cerebellar Tracts & Spinal Olivary Tract: Proprioceptive information of lower limbs to cerebellum.
• Cuneocerebellar and Rostral Spinal Cerebellar Tracts: Proprioceptive signals of upper limbs and neck to cerebellum.

Descending Pathways (Motor Tracts)

• Function: Responsible for muscle movement.

Pyramidal Tracts

• Components: Anterior and lateral corticospinal tracts.
  • Lateral Corticospinal Tract: Decussated fibers for voluntary limb movement.
  • Anterior Corticospinal Tract: Fibers decussate at spinal cord level they innervate.

Extrapyramidal Tracts

1. Rubrospinal Tract: Contralateral innervation, involved in fine motor control.
2. Reticulospinal Tracts:
   • Medial Reticulospinal Tract: Facilitates voluntary muscle contraction, increases muscle tone.
   • Lateral Reticulospinal Tract: Inhibits voluntary movement, reduces muscle tone, plays a role in automatic breathing.
3. Vestibulospinal Tract: Controls balance and posture.
4. Tectospinal Tract: Coordinates head movements with vision.

Key Points

• Ascending pathways are sensory and responsible for conscious sensation.
• Descending pathways are motor and responsible for voluntary and involuntary muscle movements.
• Tracts may have different laterality in their pathways (ipsilateral or contralateral).
• Lesions in different tracts lead to specific sensory or motor losses depending on the tract's function and pathway.