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Chapter 8

BPK 205 Chapter Notes - Chapter 8: Schwann Cell, Neuroglia, Myosatellite Cell

Biomedical Physio & Kines
Course Code
BPK 205
Parveen Bawa

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6. Draw and label the main (gross) structures of the central nervous system. In a few
sentences describe what you have drawn.
The central nervous system consists of the brain and the spinal cord. The spinal cord is
divided into the cervical, thoracic, lumbar, sacral, and coccygeal regions. The brain stem
(medulla, pons, and midbrain) leads into the diencephalon (thalamus, hypothalamus),
which is capped by the cerebral cortex.
7. What are glial cells? What are their functions? Separate these cells clearly for the PNS
and CNS [two pages, should take you ~ 25 minutes to write with no figure].
Glial cells are non-excitable cells of the nervous system. They do not carry any
information unlike neurons. They are considered support cells that keep the neurons alive
and healthy.
There are two types of glial cells only found in the PNS. These are Satellite cells and
Schwann cells.
Schwann cells form the myelin sheath of neurons that cover the axons. The Schwann
cells form internodes along the axon. This myelin sheath speeds up nerve signals that
travel along the axons. It also help regenerate axons in two different ways. One is by
providing trophic factors that promote axon regeneration, and the other is by providing
physical support to hold up axons.

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Satellite cells act as support cells for ganglia (neural cell structures found only in the
PNS) in neurons. They help maintain the physical structure of the nucleus, soma and
There are different glial cells that are found in the Central Nervous System than in the
Peripheral Nervous System. Included are the Microglia, Astrocytes, Oligodendrocytes,
and Ependymal Cells.
Microglia are modified immune cells that act as phagocytes. They are activated due to
injury or infection. Their job is to eliminate bacteria and other foreign molecules.
Astrocytes have various functions.
-They give physical support to neurons (like satellite glial cells of the PNS).
-They act as buffers (ex. Absorbing extra potassium ions to maintain a constant
extracellular environment)
-Regenerate and repair axons (similar to Schwann cells in the PNS)
-Guide neurons during development
-Maybe supply nutrients and remove wastes from neurons
-Helps form a blood, brain barrier
Oligodendrocytes cells form myelin in neurons of the brain (like Schwann cells in PNS).
One cell may wrap around multiple axons. They contain trophic factors which inhibit
regeneration and repair due to injury.
Ependymal Cells are epithelial cells which form the Ependyma, which is the epithelial
lining of the Cerebrospinal fluid vesicles in the brain and central canal of the spinal cord.
These vesicles transport cerebrospinal fluid, and help keep the brain in homeostasis. This
is a possible future source of stem cells for stem cell research
8. What is myelin, how is it formed in the PNS? [Figure + < half a page; maximum 15
Myelin is multiple layers of cell membrane wrapped around the axons of neurons. They
form the internode section of axons. It functions to speed up transfer time of action
potentials, and regenerate/repair injured axons (trophic factors, and physical support) in
the PNS.
In the PNS, myelin is formed by glial cells called Schwann cells. The Schwann cells
wrap themselves over and over again over sections of axon. The nucleus of Schwann
cells get pushed to the side to make room for these layers that wrap around the axon.
There can be very many internodes of myelin on one axon.
9. What is the difference between the cells which form myelin in the PNS and the CNS?
[< half a page, no figure, at the most 10 minutes]

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Cells that form myelin in the PNS are glial cells called Schwann cells. Schwann cells
help regenerate and repair injured axons in two different ways. One is by providing
trophic factors that regenerate axons. The other is by providing physical support for the
*Schwann cells only wrap around on axon at a time
Cells that form the myelin in the CNS are called Oligodendrocytes. Oligodendrocytes do
not help to regenerate/repair injured axons. They inhibit any repair or regeneration of
axons due to injury. Because of this, neurons in the CNS (brain and spinal cord) are
known to not be regenerated once they are destroyed.
*Oligodendrocytes wrap around multiple axons at a time
10. What are the functions of astrocytes in the CNS? {~ half a page, 10 minutes with no
The functions of astrocytes include:
Providing physical support for neural cells
Regeneration and repair of injured axons
Buffering. For example, buffering against K+ ions building up in extracellular fluid
Guides developing neuron cells
Carries away waste products
Acts as a blood brain barrier
11. Draw a typical neuron, label its various parts, tell me the main function of each
anatomical part. [Figure + < half a page of writing; 15 minutes total]
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