Nervous System Overview
Central Nervous System
- Brain
- Spinal Cord: ends at L3 at birth and L1 at maturity
Peripheral Nervous System
- Cranial nerves
- Peripheral nerves
Autonomic Nervous System
- Sympathetic system
- Parasympathetic nervous system
Spinal Cord Structure
- Conus medullaris: Termination of the spinal cord
- Filum terminale: Residual fragment of spinal cord that extends from the conus medullaris to the sacrum
- Thecal sac: Dura-surrounded sac that extends from the spinal cord and contains cerebrospinal fluid, nerve roots, and the cauda equina
- Cauda equina: Nerve roots and filum terminale that extend from the spinal cord and are surrounded by dura
Spinal Cord Layers
- Dura mater (outermost)
- Arachnoid
- Pia mater (innermost)
Functional Tracts
Ascending Tracts (Sensory)
- Dorsal columns (posterior funiculi): deep touch, proprioception, vibration
- Lateral spinothalamic tract: pain and temperature
- Ventral spinothalamic tract: light touch
Descending Tracts (Motor)
- Lateral corticospinal tract: main voluntary motor, upper extremity motor pathways are more medial (central)
- Ventral corticospinal tract: voluntary motor
Nerve Root Anatomy
Cervical Spine
- Nerve roots exit above the corresponding pedicle
- C5 nerve root exits above the C5 pedicle
- There is an extra C8 nerve root
Thoracic Spine
- Nerve roots travel below the corresponding pedicle
- T1 exits below T1 pedicle
- T12 exits below T12 pedicle
Lumbar Spine
- Nerve roots travel below the corresponding pedicle
- L1 exits below L1 pedicle
- L5 exits below L5 pedicle
Key Clinical Note: Both discs affect same nerve root in cervical spine, different than lumbar spine
Three-Column Theory
Anterior Column
- Anterior longitudinal ligament (ALL)
- Anterior 2/3 of vertebral body and annulus
Middle Column
- Posterior longitudinal ligament (PLL)
- Posterior 1/3 of vertebral body and annulus
Posterior Column
- Pedicles
- Facets
- Ligamentum flavum
- Spinous process
- Posterior ligamentous complex (PLC)
Posterior Ligamentous Complex Components
for stability
- Ligamentum flavum
- Interspinous ligament
- Facet capsule
- Supraspinous ligament