Glial Cells in the Nervous System

Glial Cells Overview

• Glial cells, derived from the Greek word "glia" (meaning "glue"), support neurons in the central nervous system (CNS).
• Essential for neuron health, glial cells outnumber neurons approximately 10:1.
• While mainly found in the brain and spinal cord, some glial cells are located in the peripheral nervous system (PNS).

Functions of Glial Cells

• Provide physical support to neurons by surrounding and holding them in place.
• Manufacture vital nutrients and chemicals needed for neuron function.
• Absorb toxins and waste materials harmful to neurons.
• Guide the development and migration of neurons during brain formation.
• Myelinate axons via oligodendrocytes, enhancing electrical signal transmission.
• Respond to nerve activity, aiding in regulating synaptic functions and communication between neurons.
• Influence learning and memory by modulating neuronal communication.
• Most brain tumors, such as gliomas, originate from mutations in glial cells.

Types of Glial Cells

• Astrocytes:

  • Star-shaped cells supporting neurons and maintaining homeostasis.
  • Deliver nutrients to neurons and regulate ions in extracellular fluid.
  • Form part of the blood-brain barrier, protecting the brain from harmful substances.
  • Active in response to nerve activity, modulating communication.

• Microglia:

  • Function as immune cells in the CNS, acting as scavengers for dead or damaged cells.
  • Involved in phagocytosis to digest harmful substances.
  • Activated during neuroinflammation, contributing to diseases like Alzheimer's.

• Oligodendrocytes:

  • Responsible for forming myelin sheaths around CNS axons for efficient signal transmission.
  • Can myelinate multiple axons simultaneously.

• Ependymal Cells:

  • Line ventricles in the brain and the spinal cord's central canal.
  • Produce and circulate cerebrospinal fluid (CSF), cushioning the brain.

• Radial Glia:

  • Act as scaffolding during brain development, guiding new neurons to final positions.
  • Can differentiate into various cell types, including neurons and astrocytes.

• Satellite Cells:

  • Found in PNS ganglia, providing structural and nutrient support to neurons.
  • Regulate the chemical environment around neurons.

• Schwann Cells:

  • Generate myelin in the PNS, insulating axons to enhance conduction speed.
  • Facilitate nerve repair and regeneration after injury.

Electrical Activity of Neurons

• Neurons generate electrical impulses and release neurotransmitters for communication.
• Resting potential is established by an uneven ion distribution, primarily maintaining sodium (Na⁺) outside and potassium (K⁺) inside.

Nerve Activation Steps

• Resting Potential: Neuron at rest exhibits a negative charge (~-70 mV).
• Action Potential: Stimulation opens ion channels, resulting in a positive charge (+40 mV) and triggering an impulse.
• Restoration: The neuron returns to resting state through sodium and potassium balance restoration.

Myelin Sheath

• A fatty layer formed by glial cells that insulates axons and accelerates nerve impulse transmission.
• Damage to the myelin sheath can lead to conditions like multiple sclerosis, disrupting communication between the brain and muscles.

This quiz explores the essential roles and functions of glial cells in the central nervous system. Discover how these non-neuronal cells support neurons and contribute to their health and functionality. Test your knowledge of the importance of glial cells in the brain and spinal cord!