1. HISTOLOGY OF NERVOUS SYSTEM

2. Nervous System The most complex system in the human body.
Formed by network more than 100 million neuron.
Each neuron has a thousand interconnection  a very complex system for communication.
Nerve tissue is distribute throughout the body, anatomically divide into : CNS & PNS.
Structurally consist : nerve cells & glial cells

3. Cells of Nervous System
NEURON
NEUROGLIA
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4. Structure of Neuron Principle cells of Nervous Tissue.
Consist of 3 parts :
CELL BODY (perikaryon/soma)
A single AXON
Multiple DENDRITES
5-150 µm

5. Cell Body (Perikaryon)
Central portion of the cell.
Generally are polygonal.
Different shape and size  characteristic regions of nervous system.
Contain :
Nucleus
Perinuclear cytoplasm

6. Ultrastructure of Neuron
Nucleus :
large, spherical to ovoid and centraly located.
a single prominent nucleolus.
Finely dispersed chromatin.

7. Ultrastructure of Neuron
Cytoplasm:
Abundant of R.E.R
Polyribosomes
Basic dyes (a+b) Nissl Bodies
lots of S.E.R.
Golgi bodies (perikaryon)
protein secreting cell

8. Ultrastructure of Neuron
Many mitochondria, most abundant in axon terminal
Extensive cytoskeleton  axonal transport
One centriole  do not undergo cell divisions

9. Dendrite and Axon Axon: Dendrites: Single process up to 100 cm
Originate from axon hillock
Devoid ribosome
Dilatation of distal portion axon terminal  end bulbs synapse
conducting impulse away from the soma
Axonal transport
Dendrites:
Multiple elongated processes
Cytoplasmic~perikaryon (devoid golgi complex)
Receiving stimuli

10. Neurons Classification
According to the size and shape of the processes: • Multipolar: the most abundant, Ex: pyramidal cells, Purkinje cells. • Bipolar: Ex: visual, auditory system. • Pseudounipolar: Ex: sensoryganglia.

11. Neurons Classification
According to the size and shape of the processes

12. Neurons Classification
According to their function:
Sensory Neuron (afferent):
Receive sensory input  conduct impulses to CNS
Motor Neuron (Efferent):
CNS  conduct impulses to muscles, glands and other neurons
Interneuron:
In the CNS as interconnectors, establish neuronal circuit between sensory and motor neuron

13. Neuron Grouping CORTEX: NUCLEI: GANGLION:
Neuron form six layers on the cerebrum.
Form three layers on the cerebellum.
NUCLEI:
In subcortical region (thalamus, midbrain, brainstem and spinal cord) neuron form irregular cluster  nuclei
GANGLION:
Cluster of neuron outside the CNS

14. Synapses Sites of impulse transmission.
Convert electrical signal into chemical signal
Permit neurons to communicate.
Types of synapses :
Axodentritic synapse.
Axosomatic synapse.
Axoaxonic synapse.
Dendrodentritic synapse.

15. Synapses

16. Neuroglial Cells Metabolic and mechanical support for neuron.
10 times abundant than neurons.
Neuroglial cells undergo mitosis.
Function: provide neurons with structural support and maintain local conditions for neuronal function.
Staining: silver or gold impregnation, histochemical technique.
Classification:
Oligodendrocytes
Astrocytes
Ependymal Cells
Microglia
Schwan cells 
CNS
PNS

17. Neuroglial Cells Astrocytes:
Pedicles binds to capillaries and to the pia mater form glial limitans.
Controlling the ionic & chemical environment of neurons
Energy metabolism
Form cellular scar tissue
Form the blood-brain barrier

18. Neuroglial Cells Protoplasmic astrocytes: Fibrous astrocytes:
Granular cytoplasm.
Envelop the surface of nerve cells and blood vessels.
Fibrous astrocytes:
Long processes.
Predominantly in white matter.

19. Neuroglial Cells Oligodendrocytes:
Produce myelin sheath. (electrical insulation) in CNS.
A single cell wrap several axons (40 to 50).
Form nodes of Ranvier

20. Neuroglial Cells Microglia:
Phagocytic cells, scattered throughout the CNS.
Derived from mesoderm.
Small cell bodies.
Their nuclei have elongated shape.
Short processes with small expansions –thorny appearance.
Functions: Clearing debris, Act as APC, protect the CNS from viruses and microorganism.

21. Neuroglial Cells Ependymal Cells:
Low columnar ciliated epithelial cells  line the ventricles of the brain & central canal spinal cord.
Formation of choroid flexus  produce CSF.
Facilitates the movement of CSF.

22. Neuroglial Cells Schwann cells: Analogue to Oligodendrocyte.
Produce myelin sheath in the PNS.

23. Nervous System is anatomically divided in to:
Central nervous system (CNS).
Peripheral nervous system (PNS).

24. The CNS Consist of : Cerebrum Cerebellum Spinal cord
No connective tissue soft, gel like
When sectioned :
White matter
Gray matter
Covered by meninges

25. Cerebrum Gray Matter: White Matter:
Contains neuronal cell bodies, dendrites and glial cells
Six layers composed of neuron
White Matter:
Contains myelinated axons and myelin-producing oligodendrocytes

26. Cerebellum Gray Matter: White Matter: Three layers:
Outer molecular layer
Central layer of large Purkinje cells
Inner granule layer
White Matter:
The same as cerebrum
19/06/2018

27. Spinal Cord Gray Matter (central) shape of “H”
Central canal lined by Ependymal cells
Legs of the “H” form :
Anterior horns
Posterior horns
Neurons : large and multipolar
White Matter (peripheral)

28. The PNS
Bundles of nerve fibers (axons) outside the CNS & surrounded by connective tissue.
Main component:
Peripheral nerves
Ganglia
Nerve endings

29. Nerve Fibers Consist of axons enveloped by a special sheath.
Group of fibers constitute the peripheral nerve.
Two types:
Myelinated fiber
Unmyelinated fiber

30. Nerve Fibers Myelinated fibers:
A single Schwann cell wraps around single axon form myelin sheath  nodes of Ranvier.
Unmyelinated fibers:
A single Schwann cell envelopes several axon.
Fibers enveloped within simple clefts of Schwann cells

31. Conduction Velocity Depend on the extent of Myelination:
Unmyelinated fibers
No nodes of Ranvier continuous conduction.
Slower conduction
Myelinated fibers:
Gap of myelin sheath (nodes of Ranvier )  saltatory conduction.
Faster conduction.

32. Connective Tissue Investments
Epineureum:
Dense collagenous Con. Tissue with thick elastic fiber
Prevent damage by overstreching
Perineureum :
Dense con. Tissue
Isolates neural environment (blood-nerve barrier)
Endoneureum:
Loose con. Tissue
Regulation of microenvironment of nerve fiber

33. Peripheral Nerve (H&E)

34. Ganglia
Ovoid structure containing neuronal cell bodies, glial cells supported by connective tissue.
Function : Relay stations to transmit impulses.
Types:
Sensory ganglia
Autonomic ganglia

35. Ganglia Cranial ganglia: Associated with the cranial nerve
Sensory Ganglia (cell bodies of sensory neuron)
Unipolar cell bodies enveloped by cuboidal capsule cells
Cranial ganglia: Associated with the cranial nerve
Spinal ganglia: Associated with the spinal nerve
Autonomic Ganglia (cell bodies of postganglionic autonomic nerves)
Multipolar neuron enveloped by satellite cells.
Some are located within certain organ (intramural).

36. Dorsal Root Ganglia

37. Autonomic Nervous System

38. Autonomic Nervous System
Sympathetic System
Parasympathetic System
The nuclei located in the thoracic and lumbar segment of spinal cord.
Preganglionic fibers leave the CNS by way of ventral roots.
The chemical mediator postganglionic fibers is norepinephrine.
The nuclei located in the medulla and midbrain and in the sacral portion of spinal cord.
Pre ganglionic fibers leave the CNS trough cranial nerve III, VII, IX and X and also trough II, III, IV sacral nerve
The ganglion located near the effector organs.
The chemical mediator pre and postganglionic fibers is acethilcholine.

39. Regeneration of CNS??
Regeneration nerve fibers in CNS is not possible, because:
An endoneureum is not present
Oligodendrocytes do not proliferate
Astrocytes deposit scar tissue (plaque)

40. THANK YOU 