Changes

*** Secreting chemokines

*** Secreting chemokines

***  Playing an important role in the entry of inflammatory cells to the CNS.

***  Playing an important role in the entry of inflammatory cells to the CNS.

** When astrocytes are lost or destroyed, the neurones become very vulnerable in the face of inflammation.

** When astrocytes are lost or destroyed, the neurons become very vulnerable in the face of inflammation.

==Oligodendrocytes==

==Oligodendrocytes==

*Myelination in the PNS is achieved by the Schwann cell, a derivative of neural crest cells, which bud off from the neuroepithelium at a very early stage of neurogenesis.  

*Myelination in the PNS is achieved by the Schwann cell, a derivative of neural crest cells, which bud off from the neuroepithelium at a very early stage of neurogenesis.  

*During development, Schwann cells engage many small axons.  

*During development, Schwann cells engage many small axons.  

*As axonal diameter increases, Schwann cells eventually relate with only a single axon c.f [[Neurones - Anatomy & Physiology#Oligodendrocytes|oligodendrocytes]].  

*As axonal diameter increases, Schwann cells eventually relate with only a single axon c.f [[Neurons - Anatomy & Physiology#Oligodendrocytes|oligodendrocytes]].  

**This single axon is enveloped in a trough by the Schwann cell processes that engulf it.  

**This single axon is enveloped in a trough by the Schwann cell processes that engulf it.  

**As the processes come together, an inner mesaxon is formed.  

**As the processes come together, an inner mesaxon is formed.  

===Axoplasmic Transport===

===Axoplasmic Transport===

*Neurones are very large cells and most of a neurones cytoplasm is present in its processes while most of the cells RNA is located in cell body (Nissl substance).  

*Neurons are very large cells and most of a neurons cytoplasm is present in its processes while most of the cells RNA is located in cell body (Nissl substance).  

*These cells have therefore evolved mechanisms to transport large macromolecules and organelles up and down processes.

*These cells have therefore evolved mechanisms to transport large macromolecules and organelles up and down processes.