Lecture on Spinal Tracts: Sensory and Motor Pathways

Introduction

• Focus: Sensory and motor tracts of the spinal cord.
• Nervous System Breakdown:
  • Central Nervous System (CNS): Brain, brain stem, spinal cord.
  • Peripheral Nervous System (PNS): Spinal nerves (somatic and autonomic fibers).
• Interaction with Environment:
  • Information travels to the brain for processing and reaction.
  • Example given: Petting an animal.

Pathways of the Spinal Cord

• Ascending Pathway: Sensory information travels from the environment to the brain.
• Descending Pathway: Motor information travels from the brain to the body.

Ascending (Sensory) Pathways

Spinothalamic Pathway

• Functions: Crude touch, pain, temperature.
• Location: Anterior and lateral (ventrolateral) in spinal cord.
• Journey:
  • Entry through dorsal ramus, root ganglion, and dorsal horn.
  • Cross to contralateral side (decussation at entry point).
  • Travel to thalamus and then somatosensory cortex.

Dorsal Column Medial Lemniscus (DCML) Pathway

• Functions: Fine touch, vibration, proprioception.
• Location: Dorsal side of spinal cord.
• Subdivisions:
  • Fasciculus Cuneatus: Upper body and arms.
  • Fasciculus Gracilis: Lower body and legs.
• Journey:
  • Entry through dorsal horn.
  • Ascend to medulla, cross to contralateral side.
  • Travel to thalamus and somatosensory cortex.

Clinical Relevance: Sensory Pathways

• Damage effects:
  • Spinothalamic Pathway: Symptoms on contralateral side.
  • DCML Pathway: Symptoms on ipsilateral side due to different decussation points.

Descending (Motor) Pathways

Corticospinal Tracts

• Functions: Voluntary motor control.
• Journey:
  • Start from motor cortex.
  • Travel through internal capsule and cross at medullary pyramids.
  • Continue down to anterior horn cells, becoming spinal nerves.

Clinical Relevance: Motor Pathways

• Damage effects:
  • Motor symptoms: Ipsilateral if spinal cord damage, contralateral if brain damage.

Clinical Syndromes

Brown-Séquard Syndrome

• Symptoms:
  • Ipsilateral loss of motor function and proprioception.
  • Contralateral loss of pain and temperature sensation.

Syringomyelia

• Symptoms:
  • Bilateral loss of pain and temperature due to central canal expansion.
  • Often presents with a 'cape-like' distribution of sensory loss.

Conclusion

• Summary:
  • Different pathways have distinct functions and regions in the spinal cord.
  • Clinical relevance is determined by decussation points.
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