Glia cells.
<P>
<Li> Ependymal cells are ciliated to circulate cerebrospinal fluid.
<Li> Oligodendrocytes  (in the CNS) and Schwann cells (in the PNS) form
myelin sheaths around axons.
<Li> Microglia protect the nervous system from microorganisms.
<Li> Astrocytes  perform  many functions, helping to form a blood-brain
barrier in the CNS.