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cells of the cns (2)
Neurons - specialized for:
a. excitation (or inhibition)
b. impulse conduction
2. Neuroglia (Glia) - interstitial cells
a. Astrocytes
b. Oligodendrocytes
c. Microglia (mesoglia)
d. Ependymal cells
grey matter
unmyelenated cell processes plus glial cells
IN CNS a cluster of nn cell bodies w/ similar fx
OUTSIDE CNS a cluster of nn cell bodies w/ similar fx
location of grey matter
a. central part of spinal cord
b. brain stem (portions)
c. cortical tissue (of brain)
White Matter
Long processes of neurons (predominantly myelinated) plus glial cells.
Functionally related processes are grouped in ______
Mixed Areas
Neuron cell bodies plus myelinated cell processes plus glial cells. Includes
portions of brain stem (medulla, pons, midbrain.)
what is the connective tissue in CNS?
** No C.T. fibers except some associated with capillaries.
T/F there is abundant capilaries in CNS
size of neuronal cell body (perikaryon)
4µm to 135 µm
describe nucleus of neuronal cell body (perikaryon)
- usually central except for the neurons of the autonomic nervous system (have eccentrically placed nuclei).
- lots of euchromatin.
- single, large nucleolus near the center of the nucleus.
What does the following describe:

-identified at the light microscopic level as blue patches (With H &
E stain).
- stacks of flattened cisternae of rough E.R. mixed with lots of free
- chromatolysis: followin
Nissl substance
Cell body (Perikaryon) contains
Golgi, mitochondria, microfilaments, microtubules.
pigments of Cell body (Perikaryon)
- lipofuscin (increases with age of cell).
- melanin: abundant in the substantia nigra of the midbrain.
axon hillock
proximal part of axon; a little thicker in diameter.
plasmamembrane of axon
cytoplasm of axon. Lacks Golgi and rER. Free ribosomes
are rare.
Axon. Describe size & branches
size varies from a fraction of a mm to several feet.

many have collateral branches which leave at right angles
- some have recurrent collaterals that curve back along originating
describe dendrites
a. much shorter than axons
b. branch dichotomously at right angles
c. contain ribosomes, Nissl, filaments, mitochondria, etc.
d. dendritic transport occurs but little is known of details
Multipolar neurons
i. many dendritic processes + 1 axon
ii. includes most neurons
Bipolar neurons
i. two processes: 1 dendrite + 1 axon
ii. location: inner ear, retina of eye
Unipolar neuron
i. 1 axon only
ii. location: retina of eye
Pseudounipolar neuron
i. modified unipolar: axonal process + dendritic process
ii. somatic sensory fibers
LARGE Neuron is also called?
How large?
Golgi Type I

perikaryon to 135µm diameter
axons to several feet
examples of Golgi type I
Pyramidal cells (cerebral cortex)
Purkinje cells (cerebellar cortex)
lower motor neurons
SMALL Neurons also called?
How small?
More prevelent than Golgi type I?
Golgi type II
1) perikaryon as small as 5µm
2) axons - a fraction of a mm. (usually unmyelinated)
3) vastly outnumber the Golgi type I cells
4) includes interneurons (internuncials)
Examples of Golgi type II
i. Stellate cell (cerebral cortex)
ii. Cell of Martinotti
iii. Granule cell
iv. Horizontal cell
Neuroglia includes:
A. Oligodendrocytes
B. Astrocytes
C. Ependymal Cells
D. Microglia
What is this describing:

1. Nucleus is spherical with medium to dense chromatin.
2. Numerous cytoplasmic processes project from the cells to wrap around
* The continued wrapping of the cytoplasmic processes forms a myelin
What is this describing:

1. nuclei are larger than other glial cells. Also, somewhat irregular in
2. contain many processes that project in several directions.
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3. the ends of the processes widen and spread ove
Astrocyte Feet
-widen and spread over the surfaces of
neurons and capillaries
-Most capillaries are
completely ensheathed by the astrocytic feet.
Function of Astrocytes
a. support
b. chemical transport (between capillaries and neurons).
Types of Astrocytes
a. fibrous - present in white matter
b. protoplasmic - present in gray matter
What is this describing:

Location: Line the ventricles of the brain and the central canal of the
spinal cord.

2. Structure:
a. cuboidal to columnar in shape
b. ciliated in the ventricles and non-ciliated elsewhere
Ependymal Cells
What is this describing:

1. small cells with dark, flattened nuclei.
2. origin & function are controversial
One School of thought believes there are two types of Microglia. Most microglia in CNS are neuroectodermal in origin, have no
known function, are called __________.
resting microglia.
One School of thought believes there are two types of Microglia. In damaged or
infected areas of the brain, a population of microglia known as __________
are identified that are derived from blood
monocytes and are therefore mesodermal in
reactive microglia
Other school of thought believes all microglia have _______ function
Neuropil at light microscopic level -
neuropil appears as a fine mottled area between
cell bodies of neurons.
Neuropil at electron microscopic level
1. conglomerate of cell bodies & cell processes of astrocytes along
w/processes of neurons (mostly unmyelinated).
2. fine intercellular spaces between cells and their processes.
3. glycosaminoglycans (hyaluronic acid, chondroitin and heparin sulfates)
present in spaces. Similar to ground substance of C.T.

Deck Info