Histology of Nervous System - medicinebau.com

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


SYSTEM



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


SYSTEM



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.


SYSTEM



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


SYSTEM



• 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


SYSTEM



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):


SYSTEM



• 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


SYSTEM



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


SYSTEM



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


SYSTEM



• 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


SYSTEM



• 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


SYSTEM



• 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


SYSTEM



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


SYSTEM



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


SYSTEM



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


SYSTEM



• 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


SYSTEM



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.


SYSTEM



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


SYSTEM



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


SYSTEM



• 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


SYSTEM



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Histology of Nervous System - medicinebau.com