Chapter 13 Lecture Notes

Introduction to the Nervous System

• Previously introduced basic nervous tissues
• Focus on the Central Nervous System (CNS): brain and spinal cord

Topics Covered

1. Spinal Cord
2. Spinal Nerves
3. Spinal Cord Tracts
   • Ascending (sensory)
   • Descending (motor)
4. Spinal Reflexes

Spinal Cord Anatomy

• Cervical Enlargement: for brachial plexus (arms)
• Lumbar Enlargement: for lumbar plexus (legs)
• Conus Medullaris: end of the spinal cord
• Cauda Equina: bundle of spinal nerves resembling a horse's tail

Meningeal Layers

• Pia Mater: innermost layer, shrink-wrapped to spinal cord
• Arachnoid Mater: circulates cerebrospinal fluid
• Dura Mater: tough outer layer

Spaces

• Subarachnoid Space: contains cerebrospinal fluid
• Epidural Space: contains adipose tissue for cushioning

Spinal Cord Stabilization

• Denticulate Ligaments: stabilize laterally
• Filum Terminale: stabilizes vertically
• Adipose Tissue: provides cushioning
• Dura Mater: follows nerve roots, forms epineurium

Cadaver Sections

• Show root layout and meningeal layers
• Distinction between ventral (motor) and dorsal (sensory) roots

Grey Matter vs White Matter

• Grey Matter: Interior, consists of horns
• White Matter: Exterior, consists of columns (information flow)

Spinal Nerves

• Ventral Root: outgoing motor signals
• Dorsal Root: incoming sensory signals
  • Dorsal Root Ganglion: contains sensory neuron cell bodies

Spinal Cord Pathways

• Ascending Pathways (Sensory):
  • Spinothalamic Pathway: Divided into anterior (crude touch) and lateral (pain and temperature)
    • Contralateral ascension
  • Posterior Column Pathway: Fine touch, vibration, pressure, proprioception
    • Ipsilateral ascension, decussates in medulla
  • Spinocerebellar Pathway: Proprioception, cerebellum processes same side body information
    • Anterior tract decussates twice, Posterior tract does not decussate

Vocabulary

• Ipsilateral: Information ascends on same side
• Contralateral: Information ascends on opposite side
• Decussate: Crossing over from one side to the other

Conclusion

• Reviewed spinal cord anatomy
• Covered major sensory ascending pathways
• Next lecture: Descending motor pathways and spinal cord reflexes