12.3

• neuroglia

  support and protect neurons

  makes up half the volume of the nervous system

  many types in CNS and PNS
• astrocytes (CNS)

  • large cell bodies with many processes
  • maintains blood brain barrier
  • creates 3D framework for CNS
  • repairs damaged nervous tissue
  • guides neuron development
  • controls interstitial movement
• ependymal cells (CNS)

  • forms epithelium that lines central canal of spinal cord and ventricles of the brain
  • produces and monitors cerebrospinal fluid (CSF)
  • possesses cilia that help circulate CSF
• oligodendrocytes (CNS)

  • small cell bodies, few processes
  • forms myelin sheath (insulator)
  • insulates myelinated axons
  • increases speed of action potentials
  • whitens nerves
• microglia

  • smallest and least numerous neuroglia
  • fine-branched processes
  • migrates through nervous tissue
  • cleans cellular debris, wastes, and pathogens
• nodes of Ranvier

  • lie between internodes
  • where axons may branch
  • faster way to transmit information (node to node)
• satellite cells (PNS)

  • surrounds ganglia (clusters of neuronal cell bodies)
  • regulates interstitial fluid around neurons
• schwann cells (neurolemmocytes) (PNS)

  • forms myeline shealth and indented folds of plasma membrane around axons
• neurolemma (PNS)

  • outer surface of Schwann cell
  • one schwann cell = sheath one axon
  • multiple schwann cells = entire axon is sheathed
• wallerian degeneration

  • any injury to the axon or nerve cell, it continuously deteriorates axon distal to injury deteriorates
  • schwann cells form path for new growth by wrapping around the new axon
  • in CNS, limited by astrocytes
  • produces scar tissues
  • releases chemicals that block regrowth