This document provides an overview of nervous tissue, including: - The nervous system is classified as the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, while the PNS includes nerves and ganglia. - Nervous tissue contains two main cell types: neurons, which transmit nerve impulses, and neuroglia, which provide structural and functional support to neurons. Neuroglia include oligodendrocytes and astrocytes in the CNS, and Schwann cells and satellite cells in the PNS. - Neurons contain a cell body, dendrites for receiving signals, and an axon for transmitting signals

1. NERVOUS TISSUE
DR POONAM SINGH
DEPARTMENT OF ANATOMY
NAIHS

2. OBJECTIVES
• Classification of the nervous system
• Components of nervous tissue
• Classification of neurons & neuroglia
• Describe myelination

3. CLASSIFICATION / DIVISION
NERVOUS
SYSTEM
CNS
BRAIN
SPINAL
CORD
PNS
SOMATIC
SPINAL
NERVES
CRANIAL
NERVES
ANS
SYMP
PARASYMP

4. INTRODUCTION – NERVOUS TISSUE
• Tissue specialized for communication
• Has well developed property of irritability & conductivity
• Ectoderm – Neuroectoderm

5. COMPONENTS
CELLS
NEURONS NEUROGLIA
CNS
OLIGODENDROCYTE
ASTROCYTES
MICROGLIA
EPENDYMAL
PNS
SCHWANN CELLS
SATELLITE CELLS
CONNECTIVE TISSUE
Structural
organization of
nervous system

6. NEUROGLIA
• Structural & functional support to the neurons.
• > than neurons ( about 5 – 10 time more)
• Dev from spongioblast
• Cannot carry impulse

7. CLASSIFICATION (according to their location)
• NEUROGLIA IN CNS
1. Astrocytes
2. Oligodendrocytes
3. Ependymal cells
4. Microglia
• NEUROGLIA IN PNS
1. Satellite cells
2. Schwann cells

8. NEUROGLIA
• Blood- brain- barrier
• Phagocytose foreign substance
• Produce CSF
• Form myelin sheath around axons

9. Astrocytes
•Create supportive framework for neurons
•Largest, most numerous
•Star shaped with dendrite like processes
•Foot processes form sleeve around capillaries
• create “blood-brain barrier”
• Two types :-
1. Protoplasmic astrocyte
2. Fibrillary astrocyte

10. Oligodendrocytes
• Smaller than astrocytes
• Create myelin sheath around axons of neurons
in the CNS.
• Myelinated axons transmit impulses faster
than unmyelinated axons

11. Ependymal cells
• line ventricles of brain & central canal of spinal
cord
• produce & help circulate CSF (cerebrospinal
fluid)

12. • Microglia
• Smallest glial cells
• “Brain Macrophages”
• Phagocytize cellular wastes & pathogens representative of
macrophage monocyte defense system
• Mesenchymal in origin

13. Schwann cells
• Surround all axons of neurons in the
PNS creating a Neurilemma around
them.
•creates myelin sheath around most
axons of PNS
Satellite cells
• support groups of cell bodies of
neurons within ganglia of the PNS

14. NEURONS
• Structural & functional units of the nervous system.
• > 100 billion
• Specialized for reception, integration, transformation & transmission of
impulse.

15. Structure of a Typical Neuron
Cell body / Nerve cell
1. Cell membrane
2. Cytoplasm
3. Nucleus
Processes/ Nerve fiber
Axon & dendrite

16. Cytoplasm
1. Neurofibrils
2. Microtubules
3. Nissl bodies
4. Mitochondria
5. Golgi apparatus
6. Lysosomes
7. Pigments
Neurofibrils filamentous strands of proteins
Nissil bodies composed of RER which contains RNA concerned with protein synthesis
Main characteristic feature of cytoplasm
NO CENTRIOLES

17. S No DENDRITES AXON
1 CAN BE > 1 SINGLE
2 BRANCH PROFUSELY FEW BRANCHES
3 BRANCHES AT AC
ANGLE
AT RT ANGLES –
COLLATERALS
4 BRANCHES TAPER DO NOT TAPER
5 SPINES NO SPINES
6 NISSL GRANULES NISSL GRANULES -
7 IMPULSES – CELL
BODY
IMPULSES AWAY
8 NO COVERING COVERING +

18. Nerve FiberDefinition: axon of nerve cell
bundles of axons  AKA Tracts in CNS
Coverings:
Epineurium
wraps entire nerve
Perineurium
wraps fascicles of tracts
Endoneurium
wraps individual axons
2 types of nerve fibers

19. MYELINATION
Process of forming a myelin sheath around
a nerve to allow nerve impulse to move
more quickly
1. Axon lying near a schwann cell
2. Invaginates the schwann cell
3. Mesaxon formed by further
invagination by the axon
4. Mesaxon elongates & begins to wind
round the axon
5. Makes several turns around the axon
6. Lipids are deposited between the
layers of mesaxon
7. The myelin sheath is formed
( layers of mesaxon + lipids)
NEURILEMMA/ NEURILEMMAL SHEATH
A thin layer of schwann cell cytoplasm &
cell membrane of schwann cells

20. STRUCTURE OF MYELINATED PERIPHERAL NERVE
Each Schwann cell myelinates only
1mm of axons
Leaving Gaps in the myelin sheath
where axon is exposed to the
exterior
NODES OF RANVIER (short gap in
MS between 2 segments)

21. UNMYELINATED FIBRE
• Remak’s fibers
• Axons are devoid of myelin
sheath
• Mesaxon does not spiral
around them

22. CLASSIFICATION OF NEURONS
BASED ON
1.POLARITY
2.FUNCTION
3.RELATIVE LENGTH OF AXONS & DENDRITES
4. SHAPE OF THE CELL BODY

23. BASED ON POLARITY
1.UNIPOLAR
2.BI POLAR
3.MULTI POLAR
4.PSEUDO UNIPOLAR

24. MORPHOLOGICAL CLASSIFICATION
( Based on polarity)
• UNIPOLAR
- Single process
- Rare in vertebrates
• BIPOLAR
- Spindle shaped
- Single axon & dendrite
- Eg:- Retina, Spiral ganglion, Olfactory neurons

25. MORPHOLOGICAL CLASSIFICATION
( Based on polarity)
• PSEUDOUNIPOLAR
- Single process- Branches into axon & dendrite
- Eg:- Spinal ganglion, Mesencephalic nucleus
• MULTIPOLAR
- Single axon, > One dendrite
- Most common
- Eg:- Cerebral cortex, Anterior horn, Autonomic ganglion

26. FUNCTIONAL CLASSIFICATION
1. Sensory neurons
2. Motor
3. Interneurons / Intercalated
ACCORDING TO LENGTH OF AXONS
1. Golgi I type
2. Golgi II type

27. • In addition:- (Based on
the shape of the cell
body)
--Pyramidal cells
-- Purkinje / Pyriform cells
-- Stellate cells
-- Glomerular cells
-- Fusiform cells
-- Amacrine cells

28. NERVE T.S ( H&E )

29. NERVE T. S. (OSMIC ACID)

30. NERVE L.S. (H&E)

31. THANK YOU