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AlyaAlya AmilaAmila FitrieFitrie , , RaditaRadita N.A. N.A. GintingGinting, , ZulhamZulhamDepartment of HistologyDepartment of Histology

Medical FacultyMedical FacultyUniversity of Sumatera UtaraUniversity of Sumatera Utara

Nerve Tissue &

Nervous System

Topics

1. Histology of Nerve Tissue

2. Histology of Central nervous System

3. Histology of Peripheral Nervous System

4. Nerve Regeneration

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Histology of Nerve Tissue

Cells of Nervous System

Neurons : receptive, integrative and motor

function of the nervous system

Neuroglial cells : supporting &

protecting neurons

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Neurons

Cell body/perikaryon

/soma

Dendrites

Axon

Cell bodyCell body : contains of nucleus, surrounding cytoplasma, exclusive of the cell processes.

Function : trophic center, receptive capabilities.

Rough endoplasmic reticulum : highly developed→ parallel cysternae. Between the cysternae → polyribosomes.

This cysternae + polyribosomes with appropriate stains → basophilic granular areas, called Nisslbodies.

Mitochondria >>> in the axon terminal

Ultrastructure of a neuronal cellbody. (From Lentz TL: Cell Fine Structure: An Atlas of Drawingsof Whole-Cell Structure. Philadelphia, WB Saunders, 1971.)

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Main types of neurons

1. Multipolar : most neuron of body

2. Bipolar : cochlear & vestibular ganglia, retina & olfactory mucosa

3. Pseudounipolar : spinal ganglia

Special types of neuron

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Neuroglia

Glial cells : 10 times abundant than neurons

Glial cells surround both cell bodies and their processes that occupy the interneuronal space

Oligodendrocytes

Schwann cells

AstrocytesEpendymalcells

Microglia

Oligodendrocytes & Schwann cell

•Oligodendrocyte : Produces the myelin sheath that provides the electrical insulation of neurons in CNS

•Schwann Cell : Produce a myelin sheath

that located around

axons in PNS

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Astrocytes

Star-shaped cells with multiple radiating processes

Astrocytes bind neuron to capillaries and to the piamater.

Astrocytes with few long processes and located in the white matter → fibrous astrocytes

Astrocytes with many short-branched processes and located in the grey matter → protoplasmic

astrocytes

Ependymal cells &

Microglia

� Ependymal cells : cuboidal or low columnar epithelial cells, lining the ventricles of the brain and central canal of the spinal cord.

� Microglia : small elongated cells with short irregular processes.

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Histology of Central Nervous

System

Central Nervous System

Cerebrum

Cerebellum

Spinal cord

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Cerebrum

Neuron types in the

cerebral cortex:

1. Pyramidal cells

2. Stellate (granul cells)

3. Cells of Martinotti

4. Fusiform cells

5. Horizontal cells of Cajal

Cerebrum (cont..)

Layers

1.Gray Matter / cerebral cortex:

a. Plexiform (molecular)

layer

b. Outer granular layer

c. Pyramidal cell layer

d. Inner granular layer

e. Ganglionic layer

f. Multiform cell layer

2.White matter

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Cerebellum

Function : coordinates muscular

activity and maintain posture

& equilibrium.

Consist of :

1. Gray matter :

• Molecular layer

• Purkinje cell layer

• Granular layer

2. White matter

Cerebellum (cont..)

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Spinal Cord

Consist of :

1. White matter, in the outer

2. Grey matter, has the shape of butterfly

Meninges

Consists of 3 layer :

1. Dura mater : composed of dense

connective tissue, continuous

with the periosteum of the skull.

2. Arachnoid : has 2 component :

• A layer in contact to dura

mater

• A system of trabeculae

3. Pia mater : loose connective

tissue containing many blood

vessels

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Blood-Brain Barrier

� BBB, a functional barrier, prevents the passage of some substances, from the blood to the nerve tissue.

� Supported by :

1. Occluding junction between

endothelial cells of blood

capillaries of nerve tissue.

2. The expansion of neuroglial cells

processes that envelop the

capillaries.

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Choroid Plexus & Cerebrospinal

Fluid

� CP, composed of loose connective tissue of

the piamater, covered by simple cuboidal or

low columnar epithelium.

� Function of CP is to elaborate CSF, that fills

ventricles, central canal of spinal cord,

subarachnoid space & perivascular space.

� CSF is clear,low density, & very low in protein

content.

Spinal cordSubarachnoid space

Perivascular space

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Histology of Peripheral Nervous

System

Peripheral Nervous System

Nerve fibers

Ganglia

Nerve endings

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Nerve fibers

�Consist of axons enveloped by a special sheath

derived from cells of ectodermal origin.

�The sheath cell of

� PNS→ Schwann cell

� CNS → oligodendrocyte

�Axon of small diameter → unmyelinated nerve fibers

�Thicker axons → myelinated nerve fibers

Nerve fibers

� E : epineurim

� P : perineurium

� F : fasiculus

� V : blood vessels

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Nerve fibers

Nerve fiber

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Nerve fibers

Electron microscope of a

peripheral nerve containing

both myelinated (M) and

unmyelinated (U) nerve

fibers.

Ultrastructural features of

myelinated & unmyelinated nerve

fiber1. Nucleus & cytoplasm of a Schwann

cell

2. Axon

3. Microtubule

4. Neurofilament

5. Myelin sheath

6. Mesaxon

7. Node of Ranvier

8. Interdigitating processes of Schwann

cells at the node of Ranvier

9. Side view of an unmyelinated axon

10.Basal lamina

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Ganglia

� Ganglia are ovoid structures

containing neuronal cell bodies

and glial cells supported by

connective tissue.

� They serve as relay stations to

transmit nerve impulses.

� There are Sensory ganglia &

Autonomic ganglia.

Sensory Ganglia

� Receive afferent impulses that go to CNS.

� Two types :

� Cranial ganglia : associated with cranial nerves.

� Spinal ganglia : associated with the dorsal root of the spinal nerves.

� Large neuronal cell bodies with prominent fine Nissl bodies surrounded by abundant small glial cells called satellite cells.

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Autonomic Ganglia

� Appear as bulbous dilatation in

autonomic nerves.

� Usually have multipolar neurons.

� Have neuronal perikaryons with

fine Nissl bodies.

� Enveloped by satellite cells.

Autonomic Nervous System

� ANS related to the control of smooth muscle, the secretion of some glands & modulation of cardiac rhythm.

� ANS are organized & regulated in the CNS.

� Anatomically, ANS composed of :� collection of nerve cell located in CNS

� fibers that leave the CNS through cranial or spinal nerves.

� nerve ganglia situated in the paths of these fibers.

� Consist of : Sympathetic & Parasympathetic System

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The Nuclei of ANS

� Sympathetic System : collection of nerve cell bodies (nuclei) located in the thoracic & lumbar segments of the spinal cord →thoracolumbar division of ANS

� Parasympathetic System : nuclei in the medulla and midbrain & sacral position of the spinal cord → craniosacral division of ANS

Nerve Regeneration

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Nerve Regeneration

Nerve cell (neuron) :

no regeneration if

soma or dendrites

injured. But, nerve

fiber injured :

regeneration (+)

Neuroglia of CNS,

Schwann cell &

ganglionic satellite

cells of PNS : able

to divide by mitosis

→ regeneration.

Degeneration &

regeneration

of peripheral

nerve

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References

� Junqueira, L.C. & Carneiro, J. Basic Histology, Text & Atlas, 11th edition, Lange Medical Books McGraw-Hill. 2005

� Gartner, L.P. & Hiatt, J.L. Colour Textbook of Histology, Third Edition. 2007

� Kierszenbaum AL. Histology & Cell Biology, An Introduction to Pathology, 2nd ed. Mosby Elsevier. 2007

� Pakurar AS, Bigbee JW. Digital Histology, an interactive CD atlas with review text, Wiley-Liss, 2004

� Berman I, Color Atlas of Basic Histology, Second Edition, Lange, 1998.

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