Notes on the Spinal Cord and Nervous System

Specific Learning Objectives

• Peripheral Nervous System (PNS)

  • Comprises the somatic nervous system and motor division of the autonomic nervous system.

• Anatomy of the PNS

  • Includes peripheral ganglia, spinal nerves, cranial nerves, and associated structures of the central nervous system (CNS).

• Main Regions of the Brain

  • Identification and understanding of significant areas in the brain.

• Functions of the Brain

  • Description of the various roles of different brain regions.

The Spinal Cord

• Location & Structure
  • Extends from the foramen magnum to the first or second lumbar vertebrae.
  • Divided into regions:
  • Cervical
  • Thoracic
  • Lumbar
  • Sacral
  • Coccygeal
  • Total of 31 pairs of spinal nerves.

Meninges

• Protective Layers
  • Dura Mater: Tough outer layer, includes the subdural space.
  • Arachnoid Mater: Middle layer, with a subarachnoid space containing cerebrospinal fluid (CSF) and blood vessels.
  • Pia Mater: Innermost layer with many small blood vessels.

Organization in the Spinal Cord

• Grey Matter

  • Composed of cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia.
  • Contains:
    • Somatic motor neurons in the ventral horn.
    • Autonomic motor neurons in the lateral horn.

• White Matter

  • Comprises myelinated axons organized into nerve tracts.

• Sensory and Motor Pathways

  • Sensory neurons enter through dorsal roots, while motor neurons exit through ventral roots.
  • Spinal nerves are mixed, containing both sensory and motor paths.

Nerve Coverings

• Connective Tissue Layers
  • Endoneurium: Surrounds individual axons (contains Schwann cells).
  • Perineurium: Surrounds a fascicle of axons.
  • Epineurium: Surrounds several fascicles and forms the external layer of the nerve.

Organization of Spinal Nerves

• Cervical Region: 8 pairs (7 vertebrae)
• Thoracic Region: 12 pairs (12 vertebrae)
• Lumbar Region: 5 pairs (5 vertebrae)
• Sacral Region: 5 pairs (5 fused bones = 1 bone)
• Coccygeal Region: 1 pair

Compendium Questions

1. Identify the major parts of the brain.
2. Discuss the main lobes, sulci, and gyri of the cerebrum.
3. What structure connects the two cerebral hemispheres?
4. Analyze the advantage of the convoluted structure of the cerebrum.
5. Differentiate between white matter and grey matter.
6. Describe the roles of the thalamus and hypothalamus.
7. Outline the functions of the brainstem.
8. Identify the functional areas of the cerebrum.
9. What information does the cerebellum process and how?
10. Where does the spinal cord begin and end in adults?
11. Where do sensory and motor nerve roots enter and exit the spinal cord?
12. What are the divisions of the autonomic nervous system (ANS) and their CNS origins?
13. Distinguish between somatic motor and autonomic motor neuron pathways.
14. Define ganglia and their significance.
15. Explain the effects of various ANS parts on the body.