Glial cells

• Glia cells origins

  Macroglia - ectoderm

  Schwann cells - neural crest

  microglia - mesoderm
• Glia

  central and peripheral NS

  do not conduct action potentials
• TYPE OF GLIA - astrocytes


  star like morphology

  ends with endfeet - connections with blood vessels and neurones

  
• GLIA - ASTROCYTE - fibrous


  ·       In white matter of brain

  ·       Brain and spinal cord divided into white and grey matter – (myelinated axons = white)

  ·       Have round cell body – few but long processes – connect to blood vessels and axons of neurones

  ·       Cell bodies arranged in rows = processes overlap

  
• protoplasmic astrocytes

  in grey matter

  processes contact blood vessels and neurones at synapses and soma

  MANY SHORT PROCESSES

  domains - little overlap of processes

  
• Radial glial cells

  present in developing brain

  two main processes - connection between ventricle wall and surface of developing brain

  function - scaffolding to assist with neuronal migration

  disappear after maturation

  
• RADIAL - Bergmann glia

  in mature brain - cerebellum

  cell body in purkinje cell layer

  few processes that extend to surface of cerebellum

  processes contact with synapses and blood vessels
• RADIAL - muller glial cells

  in retina

  longitudinal processes - contact with synapses and blood vessels
• RADIAL - Ependymal glial cells

  line ventricles (holes in brain) - not a neurone

  form choroid plexus

  FUNCTION - produce and move (have cilia) cerebrospinal fluid (CSF)
• Tanycytes

  line wall of 3rd ventricle

  long processes - extend into hypothalamus - maintain homeostasis

  processes contact neurones and blood vessels

  FUNCTION - regulation of food intake
• Function of Astrocytes

  • Uptake and buffering of extracellular K+
  • Remove glutamate from the synapse
  • Metabolic support to neurones
  • Regulate blood flow according to neuronal activity
  • Supply neurotransmitter precursors to neurones e.g. GABA and glutamate precursors
  • Protect neurones against toxic compounds e.g ammonium detoxification
  • Modulate neuronal activity
• overall function of astrocytes

  maintain homeostasis of the extracellular environment of the central nervous system to ensure optimum function of neurones
• Oligodendrocytes

  processes wrap around axons

  FUNCTION: produce myelin in CNS

  only in white matter

  each process myelinate a single axon

  
• Microglia

  small immune cells of CNS

  RESTING: short processes - constantly moving - detecting damage

  IF DETECTED: morphological change - activated

  phagocytose - kill off anything causing damage
• Schwann Cells

  FUNCTION: myelinate axons of peripheral nerves

  MYELINATING Schwann cell: entire cell wraps around axon - each cell myelinates one section of single axon

  NON MYELINATING: (Remak cells) ensheath multiple axons below 1 microM diameter into Remak fibres