Lecture Notes: The Role of Glial Cells in the Nervous System

Overview of Glial Cells

• Glial Cells are support cells for neurons.
• They are smaller but more numerous than neurons.

Types of Glial Cells in Central Nervous System (CNS)

1. Astrocytes

• Role and Importance
  • Most abundant neuroglia.
  • Deliver nutrients from capillaries to neurons.
  • Capture excess salts and neurotransmitters.
  • Involved in cell signaling.
  • Recent research links astrocytes to conditions like schizophrenia.
• Blood-Brain Barrier
  • Composed of capillary walls and astrocyte foot processes.
  • Protects neurons from direct blood interaction.
  • Astrocytes facilitate nutrient and oxygen delivery to neurons.

2. Microglia

• Function
  • Clean up damaged or dead neurons.
  • Act as macrophages; consume dead cell parts.
  • Monitor neural health.
• Research Insights
  • Potential immune presence in the brain being researched.
  • Microglia markers found in areas of cell damage in the brain.

3. Ependymal Cells

• Structure and Role
  • Resemble epithelial cells, often ciliated.
  • Line central canals of the brain and spinal cord.
  • Help circulate cerebrospinal fluid (CSF).

4. Oligodendrocytes

• Function
  • Secrete myelin sheaths around axons (called fibers in the brain).
  • Facilitate faster conduction of nerve impulses.

Types of Glial Cells in Peripheral Nervous System (PNS)

1. Schwann Cells

• Role of Myelin
  • Secrete myelin fibers for fast conduction along axons.
  • Myelin sheaths wrap around axons, not dendrites.
  • Damage to myelin is significant, as seen in multiple sclerosis.
• Nodes of Ranvier
  • Gaps between Schwann cells that enhance nerve impulse speed.

2. Satellite Cells

• Function and Knowledge
  • Encircle the cell body.
  • Exact role is not fully understood, but presumed to support the cell body.

Detailed Insight on Myelin

• Myelin Sheath Composition
  • Made of glycolipid, a fatty structure.
  • Provides insulation to axons, enhancing electrical signal speed.
  • Schwann cells, a living cell with nucleus and organelles, secrete and wrap myelin around axons multiple times.