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HISTOLOGY OF NERVOUS
SYSTEM
و من احياها
Page 1 الفريق الطبي الاكاديمي
This file contain DOCTOR SPEECH & SLIDE
Done By :-
Gharam AL-Khalaileh
Yaqeen yousef
و
HISTOLOGY OF NERVOUS
SYSTEM
و من احياها
Page 2 الفريق الطبي الاكاديمي
We have in neurosysem two type of cell:
1- Neuron that carry action potential.
2- Supported cell for neuron.
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
Glial cell like a connective tissue for the neuron.
Brain and spinal cord the only organs consist of one type of cell in the body .
Cells of Nervous System
HISTOLOGY OF NERVOUS
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Structure of Neuron
• Principle cells of Nervous Tissue.
• Consist of 3 parts :
• CELL BODY (perikaryon/soma)
• A single AXON
• Multiple DENDRITES
• 5-150 µm
Neuron is an active cell ( the most active cell
in the body ). Its cromatin not condense , also it has
very basophilic nucleolus.
Rest cell , their chromatin dense ( we cannot
see nucleolus )..
Cell Body (Perikaryon)
• Central portion of the cell.
• Generally are polygonal.
• Different shape and size characteristic regions
of nervous system.
• Contain :
• Nucleus
• Perinuclear cytoplasm
Cells that produce protein has :
- Rough ER.
- Pretend nucleolus.
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Ultrastructure of Neuron
Nucleus :
• large, spherical to ovoid and
centraly located.
• a single prominent nucleolus.
• Finely dispersed chromatin.
Cytoplasm:
• Abundantof R.E.R
• Polyribosomes
• Basic dyes (a+b) Nissl Bodies
• lots of S.E.R.
• Golgi bodies (perikaryon)
protein secreting cell
HISTOLOGY OF NERVOUS
SYSTEM
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Page 5 الفريق الطبي الاكاديمي
• Many mitochondria, most abundant
in axon terminal
• Extensive cytoskeleton axonal
transport
• One centriole do not undergo
cell divisions
Dendrite and Axon
• Axon:
• Single process up to 100 cm
• Originate from axon hillock
• Devoid ribosome
• Dilatation of distal portionaxon terminal
end bulbs synapse
• conducting impulse away from the soma
• Axonal transport
• Dendrites:
• Multiple elongated processes
• Cytoplasmic~perikaryon (devoid golgi
complex)
• Receiving stimuli
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Neurons Classification
According to the size and shape of the processes:
• Multipolar: the most abundant, Ex: pyramidal cells, Purkinje cells.
**It has cell body , a lot of dentrites, one single axon .
• Bipolar: Ex: visual, auditory system.
It is found in the sensory cells . It has 2 process ( one axon and one dentrites).
•Pseudounipolar: Ex: sensoryganglia.
It has single small process , it seems like multiple process so it is called
pseudounipolar .
According to the size and shape of the processes
According to their function:
• Sensory Neuron (afferent):
It takes the impulse from skin and send it to CNS. CNS= central nervous system .
• Receive sensory input conduct impulses to CNS
• Motor Neuron (Efferent):
HISTOLOGY OF NERVOUS
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• CNS conduct impulses to muscles, glands and other neurons
• Interneuron:
Connecting the two areas ( sensory , motor ) .
• In the CNS as interconnectors, establish neuronal circuit between sensory
and motor neuron .
Neuron Grouping
The most important cell in the body is the neuron because it cannot be divided..
• CORTEX:
• 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
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
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Neuroglial Cells
IT is like C.T for the neuron because it
support them.
Metabolic and mechanical supportfor neuron.
• 10 times abundant than neurons.
but nervous is 10 larger ( in size).
• Neuroglial cells undergo mitosis.
• Function: provide neurons with structural
support and maintain local conditions for
HISTOLOGY OF NERVOUS
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neuronal function.
• Staining: silver or gold impregnation, histochemical technique.
• Classification:
• Oligodendrocytes
• Astrocytes
• Ependymal Cells
• Microglia * Schwan 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 that cover capillary .
Astrocyte is the most abundant
Astrocyteملاحظت : اي وظٍفت نم ٌتم ذكرها فً انسلاٌد تكىن نم :
• Protoplasmic astrocytes: ( short branches . )
• Granular cytoplasm.
• Envelop the surface of nerve cells and blood vessels.
• Fibrous astrocytes:
• Long processes.(and small in number .)
• Predominantly in white matter.
CNS
PNS
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SYSTEM
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• Oligodendrocytes:
• Produce myelin sheath. (electrical insulation) in CNS.
• A single cell wrap several axons (40 to 50).
• Form nodes of Ranvier
• Differences with Schwann cell that the Schwann cell produce the myelin
sheath in the peripheral but the oligodendrocytes produce it in the central
• has a lot of processes can mylinat multiple neuron at the same time but the
Schwann cell mylinated one cell
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• Microglia:
They are the only cells in the nervous system their origin is not nervous
system not ectoderm ( it is mesoderm ).
antigen presenting cell ( APC) in the nervous system .
• 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.
• 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 by
cilia .
• CSF is very high felter plasma
• CSF is co-operation between
epedymal cell & capillary
• It is NOT epithelial cell because it is like low columnar & cuboidal cell also
it haven’t basal lamina ,connect with the under cell by processes
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• Schwann cells:
• Analogue to Oligodendrocyte.
• Produce myelin sheath in the
PNS.
• Nerve it mean the axon &
neuron it mean cell body which takes the
stain so the nerve is multiple axon they
covered with CT
• It make myline sheat for signal
axon
Nervous System is anatomically divided in to:
• Central nervous system (CNS).
• Peripheral nervous system (PNS).
The CNS
• Consist of :
• Cerebrum
• Cerebellum
• Spinal cord
• No connective tissue soft, gel like
• When sectioned :
• White matter is the axon
• Gray matter is the cell body
• Covered by meninges covered the brain in 3 layer
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Cerebrum • Gray Matter:
• Contains neuronal cell bodies, dendrites and glial cells
• Six layers composed of neuron
• White Matter:
• Contains myelinated axons and myelin-producing oligodendrocytes
• Cortex is 6 layer of neuron because each layer give different order & function
Cerebellum • Originate motor movement
• Gray Matter:
• Three layers:
• Outer molecular layer
• Central layer of large Purkinje cells
• Inner granule layer
• White Matter:
• The same as cerebrum
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SYSTEM
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Spinal Cord
• Gray Matter (central) shape of “H” inside
• Central canal lined by Ependymal cells
• Legs of the “H” form :
• Anterior horns
• Posterior horns
• Neurons : large and multipolar
• White Matter (peripheral) outside
هتن بس انمطهىب انتمٍٍز بٍىا و gili cellبامتحان انلاب ما رح ٌكىن فً تمٍٍز بٍه اوىاع ال •
central canal is ependymal cell لاوه كثٍرة و صغٍرة اما ال neuronsبٍه ال
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The PNS
• Bundles of nerve fibers (axons) outside the CNS & surrounded by connective
tissue.
• Main component:
• Peripheral nerves
• Ganglia
• Nerve endings
• The cell body is not in the PNS
Nerve Fibers
• Consist of axons enveloped by a special sheath.
• Group of fibers constitute the peripheral nerve.
• Two types:
• Myelinated fiber
• Unmyelinated fiber
• The peripheral lining by CT not meninges
• Nerve made by multiple multiple hundred of axons enclosed by simple CT
من برا مغطى بال nerveال
epineurium بعدين كل مجموعة
axon طى ب غمperineurium و
مغطى ب single axonبعدين كل
endoneurium
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• 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
• In CNS is totally unmyelinated but in PNS we have Schwann cell around
nerve either rapping incompleat or the one Schwann cell has multiple
axon that is not cover all one
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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.
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SYSTEM
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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
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Peripheral Nerve (H&E)
Ganglia
• Ovoid structure containing neuronal cell bodies, glial cells supported by
connective tissue.
• Function : Relay stations to transmit impulses.
• Types:
• Sensory ganglia
• Autonomic ganglia
فٍها وجغ ما بىقدر وحدد طبٍؼت انىجغ و مكاوه لاوه الاػصاب انً فٍها فً الامؼاء نما ٌصٍر •
involuntary مثم ال autonomic ػهى ػكس انجهد انً بتقدر تحدد فٍه وىع الانم
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• 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).
Dorsal Root Ganglia
Autonomic Nervous System
HISTOLOGY OF NERVOUS
SYSTEM
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Page 21 الفريق الطبي الاكاديمي
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