Ch 11 The Neuroglia

Neurons and Neuroglia Overview

  • Neurons

    • Functional units of the nervous system
    • Carry out electrical conduction (action potentials)
    • Fragile and require support

  • Neuroglia

    • Supportive cells of the nervous system
    • Make up roughly 50% of the nervous system
    • Not electrically excitable; do not conduct action potentials
    • Able to perform mitosis, unlike neurons which are mostly amitotic
    • Two categories based on location:
    • CNS (Central Nervous System): 4 types
    • PNS (Peripheral Nervous System): 2 types

Types of Neuroglia in CNS

  • Astrocytes

    • Most abundant type of neuroglia
    • Star-shaped (hence 'astro', meaning star)
    • Functions:
    • Nourish neurons
    • Connect neurons to blood vessels, facilitating nutrient and oxygen delivery
    • Promote interconnectivity among neurons, enhancing efficiency of the nervous system

  • Microglial Cells

    • Act as the immune defense in the CNS
    • Phagocytic nature: engulf foreign particles and debris
    • Cleanup function: eliminate dead cells, bacteria, and other unwanted substances

  • Ependymal Cells

    • Ciliated cells that line fluid-filled spaces in the CNS
    • Functions:
    • Produce and circulate cerebrospinal fluid (CSF)
    • Cilia help sweep CSF to ensure constant flow, preventing stagnation

  • Oligodendrocytes

    • Form myelin sheaths around axons in the CNS
    • Myelin insulation is crucial for rapid signal transmission

Types of Neuroglia in PNS

  • Schwann Cells

    • Myelinate axons in the PNS
    • Provide insulation effectively, similar to oligodendrocytes in CNS

  • Satellite Cells

    • Similar in function to astrocytes but located in the PNS
    • Help nourish and support neurons in peripheral nerves

Summary of Functions

  • Astrocytes: Connect/nourish neurons, facilitate synaptic connections.
  • Microglial Cells: Act as immune responders, engage in phagocytosis.
  • Ependymal Cells: Line cavities, produce/sweep CSF.
  • Oligodendrocytes: Form myelin sheaths in CNS.
  • Schwann Cells: Form myelin sheaths in PNS.
  • Satellite Cells: Support and nourish neurons in PNS.