A sneak peek at Nervous System Notes

The structural classification of neurons.

The structural classification of neurons is based on the number of processes found on a cell body.

  • Multipolar = several dendrites and one axon  (this is the most common) for example, spinal motor neurons
  • Bipolar = one main dendrite and one main axon.  An example of this would be the olfactory, inner ear and in the retina.
  • Unipolar = one process only (developed from bipolar) an example of this is the sensory neurons which take the info from the periphery to brain

Axon myelinated in the CNS and PNS.

Myelination is essentially where axons get wrapped in myelin (like a  sheath). This electrically insulates and now the axon can conduct quickly. The myelin sheath is made up of some protein but mainly fat (making it appear white).
In the CNS, the oligodendrocytes cells are the myelin sheaths around more than one axon. No neurolemma is formed as the cell bodies do not wrap around the axons, it is more like an encase
In the PNS, it is the Schwann cells that encircle PNS axons with each cell producing part of the sheath that surrounds the axons during fetal development. In the PNS, the schwann cells wrap around the Axons a lot, with them being the outer most layer while the inner layers are the myelin sheath.


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