Summary of Spinal Cord Structure and Function

GROSS FEATURES OF SPINAL CORD

  • Composed of grey matter (neurons, glial cells) and white matter (myelinated axons).
  • Grey matter forms an H-shape; contains horns (posterior, anterior, lateral).

INTERIOR STRUCTURE

  • Grey matter connected by grey commissure (contains central canal).
  • White matter divided into anterior median fissure and posterior median septum.
  • Major regions include posterior funiculus, anterior funiculus, and lateral funiculi.

NUCLEI IN GREY MATTER

  • Anterior Horn: Contains alpha (α) and gamma (γ) motor neurons.
  • Organized into medial, lateral, and central groups.
    • Medial: Dorsomedial and Ventromedial nuclei (innervate neck/trunk).
    • Lateral: Contains various nuclei mainly for limb musculature.

LAMINAR ORGANIZATION

  • Contains ten layers (laminae) recognized by Roman numerals I-X.
  • Associated with specific nuclei and functions:
    • Lamina I: Posteromarginal nucleus (pain, touch).
    • Lamina II: Substantia gelatinosa (pain, temperature).
    • Lamina III-IV: Nucleus proprius.
    • Lamina VII: Includes intermediolateral (sympathetic) and intermediomedial (parasympathetic) nuclei.
    • Lamina VIII-IX: Varies, includes various motor nuclei.

TRACTS OF SPINAL CORD

  • Tracts: Collections of nerve fibers connecting grey matter; classified as ascending (sensory) or descending (motor).

DESCENDING TRACTS

  • Corticospinal Tract: Controls voluntary muscle movement; divided into lateral and anterior tracts.
  • Extrapyramidal Tracts: Includes Rubrospinal, Vestibulospinal, Reticulospinal, Tectospinal (control reflexes, posture).

ASCENDING TRACTS

  • Carry sensory information:
    • Fasciculus Gracilis: Proprioception from lower body.
    • Fasciculus Cuneatus: Proprioception from upper body.
    • Spinothalamic Tract: Pain and temperature sensation.
    • Spinocerebellar Tracts: Body posture and equilibrium maintenance.