Back and Spinal Cord - LO 8

8. Understand the major structure of the nervous system. Detail the major structures of the central nervous system (CNS) and peripheral nervous system (PNS).

The nervous system is structured into a central nervous system (CNS) and peripheral nervous system (PNS). These systems are described separately but are functionally and anatomically continuous.

Terminology important to both CNS and PNS:

• Neuron: main unit of the nervous system

  • Composed of 3 main structures:

    • Cell body

    • Dendrite(s): process(es) that carry impulses to the neuronal cell body

    • Axon: process that carry impulses away from the neuronal cell body

      • Nerve fiber: composed of axon and surrounding connective tissue (CT)

Central Nervous System

• Composed of: brain and spinal cord

• Terminology:

  • Nucleus: cell bodies of neurons collection in CNS

  • Tract: nerve fiber collection in CNS

  • Gray matter: composed of cell bodies

  • White matter: composed of systems of interconnection (processes such as axons)

Peripheral Nervous System

• Composed of: nervous tissue outside of CNS

  • 12 pairs of cranial nerves and 31 pairs of spinal nerves

  • Spinal nerves typically form complex associations, called plexuses, from which named nerves arise

• Terminology:

  • Nerve: nerve fiber bundles, associated connective tissue, vasculature

  • Ganglion: cell bodies of neurons collection in PNS