Spinal Cord Structure and Function

Overview of the Spinal Cord

• Ventral Root & Dorsal Root
  • Dorsal Root Ganglion: A cluster of cell bodies where sensory information enters the spinal cord.
  • Ventral Root: Carries motor information away from the spinal cord.
  • Spinal Nerve: Formed from the merging of the dorsal and ventral roots.

Information Flow in the Spinal Cord

• Sensory Information
  • Entering through the dorsal root.
  • Specifically associated with the posterior (back) horns of the spinal cord.
• Motor Information
  • Exiting through the ventral root.
  • Related to the lateral and anterior horns of the spinal cord.

Spinal Cord Tracts

• Definition: Collections of fibers (axons) in the Central Nervous System (CNS).
• Two Main Types:
  • Ascending Tracts: Carry sensory information up the spinal cord to the brain.
  • Descending Tracts: Carry motor information down the spinal cord from the brain.

Naming of Tracts

• Tracts are typically named based on their origin and termination.
• Examples:
  • Ascending Tracts:
  • Spinothalamic Tract: Originates in the spinal cord and terminates in the thalamus (relays sensory information).
  • Lateral Spinocerebellar Tract: Originates in the spinal cord, terminates in the cerebellum (involved in proprioception).
  • Descending Tracts:
  • Corticospinal Tract: Originates in the cortex of the cerebrum, terminates in the spinal cord (responsible for voluntary motor control).

Neuronal Pathways

• Sensory Neuron Pathway:
  • Sensory neurons enter through back of the spinal cord, travel up through ascending tracts to specific locations in the brain (e.g., cerebellum or thalamus).
• Motor Neuron Pathway:
  • Motor commands originate from the cortex, descend through the corticospinal tract, exit the spinal cord via the ventral root to stimulate muscles.

Summary

• Sensory information is always ascending, while motor information is descending in the spinal cord.
• Understanding the organization of spinal cord tracts facilitates comprehension of how the body processes and responds to sensory and motor information.