13.3 Neuroglia

• Four types of neuroglia in CNS are astrocytes, oligodendrocytes, microglia, and ependymal cells. Two types of neuroglia in PNS are satellite cells and schwann cells 
• Neuroglia. Cells by size, intracellular organization, presence of cytoplasmic processes, staining properties 
• Neuroglia. Astrocytes. Largest and most numerous, poorly understood
• Neuroglia. Astrocytes. Control interstitial environment. Large number of cytoplasmic processes, pedicels, increase surface area around neurons
• Neuroglia. Astrocytes. Maintain the blood brain barrier. Cytoplasmic processes cover capillaries within CNS, interrupted only by neuroglia
• Neuroglia. Astrocytes. Maintain the blood brain barrier. Chemicals secreted maintain blood brain barrier (BBB) that isolates CNS from general circulation 
• Neuroglia. Astrocytes. Form a three dimensional-framework for the CNS. Microfilaments in astrocytes extend across the cell, providing strength in framework for support at neurons of brain and spinal cord
• Neuroglia. Astrocytes. Repair damaged nervous tissue. Repair, stabilize, produce scar tissue
• Neuroglia. Astrocytes. Guide neuron development. Direct growth and interconnection of developing neurons through secretion of chemicals (neurotropic factors)
• Neuroglia. Oligodendrocytes. Have slender fewer shorter cytoplasmic extensions, smaller cell bodies
• Neuroglia. Oligodendrocytes. Processes contact neurons and tie axons together
• Neuroglia. Oligodendrocytes. Improving neuron performance by wrapping axons in myelin, material with insulating properties
• Neuroglia. Oligodendrocytes. Large areas wrapped in myelin are internodes
• Neuroglia. Oligodendrocytes. Small gaps between myelin sheaths produced by adjacent oligodendrocytes are called myelin sheath gaps or nodes of ranvier
• Neuroglia. Oligodendrocytes. Region dominated by myelinated axons is white matter
• Neuroglia. Oligodendrocytes. Region dominated by cell bodies, dendrites, unmyelinated axons is gray matter 
• Neuroglia. Microglia. Smallest, slender cytoplasmic process with many fine branches
• Neuroglia. Microglia. Appear early in development through division of mesodermal stem cells
• Neuroglia. Microglia. Migrate to CNS as it forms, remain in nervous tissue
• Neuroglia. Microglia. Are phagocytic cells of CNS, engulfing cellular waste
• Neuroglia. Microglia. Protect CNS
• Neuroglia. Microglia. Only 5% of neuroglia, but when infected/injured, they increase
• Neuroglia. Ependymal cells. Ependyma is cellular layer lining ventricles of brain and central canal of spinal cord
• Neuroglia. Ependymal cells. Ependyma. Cerebrospinal fluid (CSF) provides protective cushion and transport 
• Neuroglia. Ependymal cells. Ependymal cells are cuboidal to columnar in form
• Neuroglia. Ependymal cells. May act as receptors monitoring CSF
• Neuroglia. Ependymal cells. Have cilia and microvilli to help
• Neuron cell bodies in the PNS are clustered together in structures called ganglia
• Axons are bundled together and wrapped in connective tissue forming peripheral nerves 
• Neuroglia. Satellite cells. Surround neuron cell bodies in peripheral ganglia
• Neuroglia. Satellite cells. Regulate exchange of nutrients/wastes between cell body and extracellular fluid
• Neuroglia. Satellite cells. Isolate neuron from stimuli not intended to pass from neuron to neuron
• Neuroglia. Schwann cells. Covers peripheral axons, (un)myelinated
• Neuroglia. Schwann cells. Axolemma is the plasma membrane of axon
• Neuroglia. Schwann cells. Neurolemma is cytoplasmic converting provided by schwann cell
• Specifically, what cells help maintain the blood brain barrier (BBB)?

  Astrocyte.
• What is the name of the membranous coating formed by oligodendrocytes around CNS axons?

  Myelin.