Basic Neuroanatomy

Oligodendrocytes

• Responsible for the formation of myelin in the central nervous system
  • Myelin provides electrical insulation that allows for saltatory conduction, the speed of which is determined by the length of the internodal myelin segments. Larger axonal diameters conduct faster than smaller diameters.
  • Oligodendrocytes have condensed, rounded nuclei and unstained cytoplasm.

Oligodendrocytes vs. Oligodendroglioma

Astrocyte-Oligodendrocyte crosstalk

• Communication occurs by direct cell-cell gap junctions, as well as secreted signaling molecules.
• The importance of astrocyte-oligodendrocyte communication is made apparent in primary astrocytopathies such as Alexander disease, and osmotic demyelination syndrome.
  

Ependymal cells

• Produces and facilitates the movement of cerebrospinal fluid (CSF).
• Lines the ventricles and central canal of the spinal cord.
• Resembles simple cuboidal or columnar epithelium with some cilia and microvilli on histopathology.

Microglia

• The primary immune cell of the central nervous system.
  • Responsible for antigen presentation,
  • Activates in response to tissue damage and ischemic injury. Once activated, becomes a motile, phagocytic cell (adept for neuronophagia) which forms reactive oxygen species and secretes cytokines and proteases.
• The smallest and rarest glial cell.
• Derived from bone marrow/monocytes and enter the CNS in the perinatal period.
  • All other glial cells and neuronal cells are derived from neural tube cells.

Neuronal cells

• Responsible for receiving, integrating, and propagating information to other cells.
• Contains three parts; dendrites, cell body, and axon(s).
  • Dendrites
    • Receive information from other neurons at synapses.
    • Changes in dendritic spines are critical for neural plasticity that occurs during development and learning.
  • Cell body
    • The main synthetic and trophic center of the cell, it contains the nucleus and most organelles.
    • Easily identified by a large central and euchromatic nucleus with a prominent nucleolus.
    • Basophilic clumps of polyribosomes are called Nissl bodies.
  • Axons
    • Conducts information to muscles, glands, or neurons.
    • Axons terminate at synapses.
• There are a few named neurons to be aware of:
  • Pyramidal Cells: The prototype cerebral neuron, present in the cortex and hippocampus, with large triangular cell bodies.
  • Stellate Cells: Described as GABAergic inhibitory interneurons that control Purkinje cell activity in the cerebellum.

• • Purkinje cells: Large distinct neurons in the cerebellum with a prominent pink cell body and extensive dendritic tree.
    • These degenerate in various cerebellar degeneration syndromes (e.g. alcohol, chronic phenytoin use, or anti-Yo paraneoplastic syndromes).