Gray and White Matter in the Central Nervous System

Overview

• The central nervous system (CNS) includes the brain and spinal cord.
• CNS is composed of two types of matter: gray matter and white matter.
  • Gray Matter: Contains most of the neuron somas.
  • White Matter: Contains most of the myelinated axons.
• The naming is based on the appearance of tissue when prepared.

Structure and Distribution

Spinal Cord

• Gray Matter: Mostly on the inside, forming an "H" or butterfly shape.
• White Matter: Mostly on the outside, surrounding the gray matter.
• Illustration: Cross-sections of the spinal cord show gray matter inside and white matter outside.

Brain

• Gray Matter
  • Mostly on the outside of the brain.
  • Forms a layer known as the "cortex."
    • Cerebral Cortex: Covers the cerebrum.
    • Cerebellar Cortex: Covers the cerebellum.
  • Also forms "nuclei": Deep gray matter areas within the brain.
• White Matter
  • Mostly on the inside of the brain, beneath the cerebral cortex.
  • Also found in the brain stem.

Tracts

• Collections of axons traveling together in the CNS.
• Tracts carry similar types of information from one part of the CNS to another.

Functions of the CNS

• Composed of numerous neurons with diverse functions.
• Neurons are involved in:
  • Motor, sensory, and autonomic functions (similar to PNS involvement).
  • Higher functions of the nervous system, including cognition, emotion, and consciousness.

Key Points

• Gray matter is composed mainly of neuron somas.
• White matter is composed mainly of myelinated axons.
• The distribution pattern of gray and white matter differs between the brain and spinal cord.
• The cerebral cortex and certain brain areas are crucial for higher nervous system functions.