Supporting Cells of the Nervous System
There are several types of supporting cells that occur in
both the CNS and the PNS.
• None of them conduct impulses, instead they
“assist” neurons.
• As a group they are called neuroglia or “glial” cells,
(means “nerve glue”) found in between neurons.
Different cells do different jobs.
• In the CNS the cell is called the oligodendrocyte
• In the PNS the cell is the Schwann cell.
Supporting Cells of the Nervous System
Functions of neuroglia:
1)support, protect and separate neurons
2) act as phagocytes to clean up worn-out neuron
organelles.
3) Electrically insulate neurons by forming a myelin
sheath.
4) increase the speed of the action potential (electrochemical message) in those cells that have a myelin
sheath.
Supporting Cells of the Nervous System
Schwann cells• Additional functions- they make it possible for some
peripheral nerves that are damaged to regenerate
their axons. Peripheral neurons will not regenerate
if the cell body is damaged.
• NOTE: This only occurs in the PNS. CNS neurons do
not regenerate their axons at all.
Supporting Cells of the Nervous System
Schwann cell structure:
Schwann cells can also surround other
unmyelinated neurons in clusters to give them
insulation.
Supporting Cells of the Nervous System
Schwann cells structure:
• They do all this by making a myelin sheath around
many of the neuron processes in the PNS. They wrap
themselves very tightly around the process of a
neuron.
• The cytoplasm and nucleus is squeezed to the
surface of the wrapping called the neurolemma.
• The layer that lies against the axon is just many layers
of the fatty plasma membrane- called the myelin
sheath.
Supporting Cells of the Nervous System
Schwann cells structure:
• The myelin sheath is many Schwann cells,
wrapped up, side-by-side along a neuron
axon. This type of neuron is said to be
“myelinated”.
• The Schwann cells don’t touch each other, so
there are spaces between, called Nodes of
Ranvier. These allow for faster impulse
conduction.