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BIOC21H3 Study Guide - Franz Nissl, Neuroglia, Axon


Department
Biological Sciences
Course Code
BIOC21H3
Professor
Stefan Rusyniak

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LECTURES 10 & 11 NERVOUS TISSUES
Cells of the CNS
NEURON
GLIAL CELLS
MICROGLIA
EPENDYMAL
CELLS
Oligodendr-
ocyte
Astrocyte
Structure
- Cell body (soma or perikaryon), nucleus,
axon, dendrites, abundant Nissl substance
(RER), myelin
- Myelin
Protects and insulates nerve fiber
(axon)
Helps speed up transmission of
impulse salutatory conduction
Composition: 70-80% lipid, and
some protein made from a
cellular membrane
In the CNS, is generated by
oligodendrocytes
In the PNS, is generated by
Schwann cells
- Cell body
separate from
myelin
- Nucleus
- Unbranched
cytoplasmic
processes
- Largest neuroglial cells
- Smallest
neuroglial cells
- Oval cell bodies
- Believed to
originate in the
bone marrow
- Part of the
Mononuclear
Phagocyte System
(MPS)
- Originate from
monocytes
- Form a simple
columnar
covering the
ventricles of the
CNS
- In contact with
astrocytes
forms a barrier
- Not true
basement
membrane
- Have surface
cilia and
microbilli
Nucleus
Large, very pale nucleus (lots of
euchromatin) with a dense nucleolus
(Owl’s eye nucleus)
Oval
nucleus,
clear space
around
nucleus
Small, elongated
nucleus
Processes
- Cellular processes not normally visible
(not all neurons look the same)
- Many, short highly branched dendrites
- One axon transmits action potential to
other cells/neurons
Un-branched
cytoplasmic
processes
wrap around
nerve fibers
A single
Short, “spiny”
processes
processes appear to
have small spikes

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- Dendrites
Short afferent processes
Variable diameter along length it
changes
May display Nissl substance
Unmyelinated
Some have „dendritic spines
important for proper brain
development; highly elongated in
young people and shorten with age
- Axon
Axon Hillock is normally free of
any ribosomes or RER = poor
staining Initial Segment follows
Less Nissl substance, pale
Diameter affects speed of impulse
transmission diameter more
uniform throughout
More mature than dendrites
Can be myelinated (increases
action potential speed) or
unmyelinated (does not mean
“naked”)
Can have collateral braches
End in telodendria and terminal
boutons at the synapse
cell can thus
produce
several
internodes
Abundance
10% of cells in the CNS
90% of cells
in the CNS
90% of cells in the CNS
Not common or
easily identifiable
on slides
Different
Types
1) Unipolar: Other cell‟s axons terminate
on the cell body no dendrites, one
axon
2) Bipolar: A single dendrite enters the
1) Protoplasmic Astrocytes
Found mostly in gray
matter
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