Neuroglial Cells and Their Functions

Neuroglial Cells: Support Cells of the Nervous System

Terminology

• Nerve:
  • Found only in the Peripheral Nervous System (PNS).
  • Groups of axons wrapped together in connective tissue.
• Ganglia:
  • Found only in the Peripheral Nervous System (PNS).
  • Collections of cell bodies of neurons grouped together in masses.
  • Example: Sympathetic trunk ganglia.

Neuroglial Cells Overview

• Support cells for neurons.
• Critical for protecting the health and life of neurons, which need to last a lifetime.

Neuroglial Cells of the Peripheral Nervous System (PNS)

Schwann Cells

• Composed of a fatty myelin sheath.
• Function:
  • Wrap around axons to insulate and protect them.
  • Increase the speed of nerve impulses.
• Structure:
  • Schwann cell nucleus.
  • Myelin sheath.
• Nodes of Ranvier:
  • Gaps or nodes between Schwann cells (myelin sheath).
• Saltatory Conduction:
  • Electrical impulse jumps from one node of Ranvier to the next.
  • Much faster than the electrical signal traveling the entire length of the axon.

Neuroglial Cells of the Central Nervous System (CNS)

Ependymal Cells

• Function:
  • Circulate cerebrospinal fluid (CSF).
  • Allow fluid exchange between the brain, spinal cord, and CSF.
• Cerebrospinal Fluid (CSF):
  • Specialized clear fluid found in the brain and spinal cord.
  • Functions:
    • Protects the brain and spinal cord.
    • Enables the brain to float, preventing it from hitting the skull.
• Ventricles of the Brain:
  • Spaces or holes inside the brain that produce CSF.
  • Ependymal cells circulate CSF throughout the brain and spinal cord acting almost like a filtering system.

Oligodendrocytes

• Act as insulation for axons in the Central Nervous System (CNS).
• One cell can cover multiple neurons via extensions.

Astrocytes

• Control the chemical environment of neurons.
• Neurons require a very specific chemical environment to function and conduct electrical impulses.
• Wrap around blood capillaries.
• Blood-Brain Barrier:
  • Created by astrocytes wrapping around capillaries.
  • A physical barrier that only allows certain substances to pass through.

Microglial Cells

• Protect the CNS by phagocytizing dead cells and pathogens.
• Function:
  • Eat up any dead cells.
  • Eliminate pathogens inside the brain and spinal cord.

Summary of Neuroglial Cells in the CNS

• Capillaries: Supply blood to the brain and spinal cord.
• Astrocytes: Wrap around capillaries, forming the blood-brain barrier.
• Oligodendrocytes: Wrap around axons, providing insulation.
• Microglia: Clean up dead cells and pathogens.
• Ependymal Cells: Circulate cerebrospinal fluid within the brain and spinal cord.