Lecture Notes: Spinal Cord Structure and Function

Overview

• Understanding the spinal cord structure and function.
• Focus on spinal nerves, tracks (nerve fibers connecting brain to body), reflexes, and nerve plexus.

Spinal Cord Structure

• Spinal cord connects brain to peripheral nervous system.
• Consists of ascending (sensory) and descending (motor) tracts.
  • Ascending Tracts: Carry sensory information to the brain.
  • Descending Tracts: Carry motor commands from the brain.
• Spinal Nerves: Total of 31 pairs emerge laterally from the cord.
  • Cervical and lumbar regions are thicker due to nerve cell bodies and tracks.

Spinal Cord Anatomy

• Extends from the brainstem to L1 or L2 (conus medullaris).
• Cauda Equina: Bundle of nerve roots, resembles a horse's tail.
• Spinal cord stops growing sooner than the vertebral canal, allowing for CSF sampling/ injections.

Nerve Anatomy

• Spinal nerves exit through intervertebral foramen.
  • Sacral nerves exit through sacral foramina.
• Cervical Nerves: Eight pairs, despite seven vertebrae.
  • C1 nerve exits above C1 vertebra; C8 exits below C7.
• Dermatome map shows skin areas served by each spinal nerve.

Microscopic Structure

• Dorsal and Ventral Roots:
  • Dorsal root: Carries sensory fibers (blue color, sensory).
  • Ventral root: Carries motor fibers (brings motor commands out).
  • Dorsal Root Ganglion: Contains sensory neuron cell bodies.

Rami

• After exiting the spinal column, nerves split into rami
  • Rami carry both sensory and motor fibers.
  • Larger anterior rami serve front body and extremities.

Internal Spinal Cord Structure

• Grey Matter: Inner core (cell bodies, integration of reflexes).
• White Matter: Outer core (tracks for nerve fibers).
• Butterfly Shape: Grey matter divided:
  • Posterior Horn: Sensory nuclei.
  • Lateral Horn: Autonomic nuclei.
  • Anterior Horn: Somatic motor nuclei.
• Central Canal: Carries cerebrospinal fluid.

Reflexes and Functional Aspects

• Reflexes: Automated responses, crucial for bodily functions.

Summary

• Understanding the arrangement and function of spinal cord elements helps in grasping nervous system operations.
• Important for diagnosing and treating spinal injuries and diseases.