There are two main cell types in the nervous system: neurons and neuroglia. Neurons are excitable cells that conduct nerve impulses, while neuroglia provide support and insulation. Neuroglia, also called glial cells, make up about half the volume of the central nervous system and include astrocytes, oligodendrocytes, microglia, ependymal cells, and Schwann cells. Astrocytes help nourish neurons and form the blood-brain barrier, while oligodendrocytes and Schwann cells create myelin sheaths around axons. Neurons consist of a cell body, dendrites that receive signals, and an axon that conducts signals away.

1. NEUROGLIA
(GLIA)
& NEURON
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PREPARED BY,
Mr. Vipin Chandran

2. CELLS OF THE NERVOUS SYSTEM
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Two types of cells make up the nervous
system:
1. Neuroglia:
• Make up about half the volume of CNS.
• They were “glue” that held nervous tissue
together.
2. Neurons
• Excitable cells that conduct impulses
• It respond to stimulus and convert it into action
potential.

3. 1.NEUROGLIA OR GLIA
• Neurolgia are smaller than neuron.
• They are 5 to 25 times more numerous.
• Glia do not generate or propagate action
potentials.
• Glia means ‘glue’
• They can multiple and divide in the
mature nervous system
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4. TYPES OF
NEUROGLIA
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1. Astrocytes
2. Microglia
3. Ependymal cells
4. Oligodendrocytes
5. Schwann cells
6. Satellite cells
First 4 types are found in the CNS and
remaining two present in PNS

5. 1. ASTROCYTES
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• Star shaped glia (greek: astron-star)
• Found only in CNS
•Largest and most numerous type of glia
•Tiny delicate points extend through brain
tissue attaching neurons and tiny blood
capillaries
•‘Feed’neurons by taking up glucose from
blood, converting to lactic acid and giving
to neurons
• It contain microfilament that give strength
to neuron.

6. •Endothelial cells creates “blood brain barrier”
which restricts movement of substance between
blood and interstitial fluid of the CNS.
• It help to maintain chemical environment for
generation of nerve impulse.
•It also play role in learning and memory.
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7. 2. MICROGLIA
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•Small, usually stationary cells found in CNS
• Also known as Brain’s immune cells
•In inflamed or degenerating brain tissue,
microglia enlarge, move about, and
carry on phagocytosis
•They engulf and destroy micro
organism and tissue debris
•Although named as glia, are
functionally and developmentally
unrelated to nervous system cells

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9. 3. EPENDYMAL CELLS
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• They are cuboidal to columnar cells arranged in
single layer posses microvilli and cilia.
•Thin sheets that line fluid filled cavities in
brain and spinal cord.
•It produce, monitor, and assist circulation of
CSF.

10. 4. OLIGODENDROCYTES
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•Smaller than astrocytes and have fewer
processes
•Oligo-few, dendro-branch, cyte-cell :
meaning "cells with fewer branches"
•Some lie clustered around nerve cell body,
some arranged in rows between nerve fibre
in brain and spinal cord
•Help hold nerve fibre together
•Important function : produce fatty
myelin sheath around nerve fibre of CNS

11. Oligodendroc
yte
Axon
Nucleus
Myelination in the
Central Nervous
System
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12. 5. SCHWANN CELLS
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• Found only in PNS
• Also called as ‘Neurolemmocytes’
•Like oligodendrocytes, they
form myelin sheath around
axons.
•Support nerve fibre and form myelin sheath
around them
•Many schwann cells wrap around single
neuron
•Myelin sheath is formed by layers of
Schwann cell membrane containing

13. •Microscopic gaps in the sheath,
between adjecent Schwann cell-
Node of Ranvier or myelin sheath
gaps
•The myelin sheath and gaps in nerve
fibre are important for transfer of nerve
impulses
•Schwann cell’s nucleus and cytoplasm
are squeezed to perimeter to form
neurilemma.
•neurilemma important for
regeneration of injured nerve fibres.
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14. Node of
Ranvier
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15. •Nerve cells with many Schwann
cells attached and having thick
myelin sheath -White fibre or
Myelinated fibre
•Several nerve fibres held by single
Schwann cell and does not wrap
around to form thick myelin sheath –
Grey fibre or Unmyelinated fibre
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16. 6. SATELLITE
CELLS
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• It surrounds cell bodies of neurons of PNS
ganglia.
• It regulate exchange of materials between
neuronal cell bodies and interstitial fluid.

17. Node of
Ranvier
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18. 2. NEURONS
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•The human brain estimated to
contain about 100 million , or 10% of
total neurons of nervous system
• Neuron consist of:
i. Cell body
ii. Axon
iii. Dendrites
iv. Axon ends

19. I. CELL BODY
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• Largest part of a nerve cell
•Contain nucleus, cytoplasm and
various organells like mitochondria
and golgi apparatus
•Also called as "perikaryon" or “soma” ;
meaning surrounding the nucleus
•Plasma membrane encloses the whole
neuron.
•RER and attached ribosomes provide
proteins for neuron.
• Some of the proteins are processed.

20. •Neurotransmitters are
proteins packaged in
vesicles that aid
neurotransmission
•Other proteins used
for repair of neuron
•Mitochondria replicate
themselves in the cell
body: some transported
to end of axon to
provide energy for signal
transduction
• Cluster of RER termed
Nissl Bodies
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21. II. DENDRITES
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•Branch extensively from
cell body like tiny tree
• Greek word : tree
•Distal end of sensory
neurons called receptors :
receive stimuli that initiate
nerve signals
•some dendrites in brain
have knoblike dendritic
spines: serve as
connection point of other

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23. III. AXON.
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•Extend from tapered portion of cell body called
axon hillock
•Conduct impulse away from cell body.
•Axon has side branches called Axon collaterals
•Distal ends of axon form branches called
telodendria and each terminate in a synaptic knob

24. •Site of communication between two
neuron and a effectors cell is called
synapse.
•Both synaptic end bulb and varicosities
contains tiny membrane enclosed sacs
called synaptic vesicles that store
chemical neurotransmitters.
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26. CLASSIFICATION OF NEURON
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Structural classification
1. Multipolar
2. Bipolar
3. Unipolar
Functional Classification
1. Afferent neurons (Sensory)
2. Efferent neurons (Motor)
3. Interneurons (Association)

27. STRUCTURAL CLASSIFICATIONL
Classified according to number of
extensions from cell body
 1. Multipolar neurons: one axon but
several dentrites, most of the neurons in
brain and spinal cord are multipolar.
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28. 2. BIPOLAR NEURONS: One Axon
And One Heavily Branched Dentrite,
Least Numerous Kind And Found In
Retina , Inner Ear And Olfactory
Pathway
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29. 3. Unipolar neuron : single process
extending from the cell body, which
branches into central process
(towards CNS) and peripheral process
(away from CNS), process forms a
single axon and conducting impulse
away from dentrite, they are always
sensory neurons.
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30. FUNCTIONAL CLASSIFICATION
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Classified based on direction of
conduction of nerve impulse.
1.Afferent neuron: to
spinal cord or brain
2.Efferent neuron: away
from brain or spinal
cord to muscle or
gland
3.Interneurons:
mainly located
within the CNS
between sensory
and motor neuron.

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