Chapter 13 Lecture Notes

Introduction to the Central Nervous System (CNS)

Regions of the Spinal Cord:
- Cervical Enlargement: Increases neural traffic through brachial plexus (arms).
- Lumbar Enlargement: Allows neural traffic through lumbar plexus (legs).
- Conus Medullaris: End point of the spinal cord, around L1 to L2.
- Cauda Equina: Nerve bundle from L3 to S5, looks like a horse’s tail.
Meningeal Layers:
- Pia Mater: Innermost, adheres to the CNS surface.
- Arachnoid Mater: Between pia mater and dura mater, circulates cerebrospinal fluid in the subarachnoid space.
- Dura Mater: Outermost, tough protective layer.
- Spaces:
  - Subarachnoid Space: Contains cerebrospinal fluid.
  - Epidural Space: Contains adipose tissue for cushioning.
Spinal Cord Stabilization:
- Dura mater follows nerve roots, anchoring spinal cord.
- Denticulate ligaments stabilize laterally.
- Terminal filum and coccygeal ligament stabilize vertically.

Gray Matter: Inside (horns), horizontal information.
White Matter: Outside (columns), vertical information.
Roots:
- Dorsal Root: Sensory input, has ganglion.
- Ventral Root: Motor output, no ganglion.

Spinothalamic Pathway:
- Anterior Tract: Carries crude touch and pressure, decussates immediately in spinal cord, ascends contralaterally.
- Lateral Tract: Carries pain and temperature, similar decussation and ascension as anterior.
Posterior Column Pathway:
- Carries: Fine touch, vibration, pressure, proprioception.
- Subdivisions:
  - Fasciculus Gracilis: Info from T7 and below.
  - Fasciculus Cuneatus: Info from T6 and above.
- Decussates in Medulla Oblongata, enters medial lemniscus.
Spinocerebellar Pathway:
- Carries proprioceptive information directly to cerebellum.
- Posterior Tract: Ascends ipsilaterally.
- Anterior Tract: Decussates twice, still processed ipsilaterally in cerebellum.