Tishk International University

Faculty of Pharmacy

Department of Pharmacy

HISTOLOGY – 110

Primary Basic Tissues of the Body

The Nervous Tissue Part -B

First Grade – Spring Semester 2019-2020

Instructor : Dr. Hiwa Bakir Banna

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Myelinated axon

Non myelinated axon

Peripheral nerve fiber showing

Node of Ranvier X 400Peripheral nerve fiber in sections X 100

Classification of neurons according to Function:1-Sensory neuron or afferent towards CNS. Carry messages in from the body's

tissues and sensory receptors to the CNS for processing.

2- Motor or efferent neurons carry instructions out from CNS to the body's tissues.

The simplest example is the knee jerk?

3-Interneurons(integration) In the CNS- process information between the sensory input and

motor output.

Classification of neurons according to shape:Neurons are classified according to a variety of criteria:

The most abundant and important type is Multipolar neurons present in both CNS and PNS

such as :

Pyramidal neurons in cerebral cortex gray matter

Purkinje neurons in cerebellar cortex

Stellate star shaped neurons in gray matter of spinal cord

And ganglionic neurons of the autonomic nervous system such as bipolar, multipolar and

pseudounipolar neurons.

2-Neuroglia :

Neuroglia cells provide metabolic and structural support for neurons, the number of

glia cells in the brain are ten time more than the number of neurons. Neurons would not be

able to function without support and protection from these glia cells. Glia cells also provide

insulation for nerve fibers(myelin sheath),nutrition, homeostasis and phagocytic activities.

They do not conduct impulses but have retained the ability to divide .

(Most brain tumors are caused by mutations in glia cells).

There are six types of neuroglia cells:

Neuroglial types in Central Nervous System are: 1-Astrocytes, (nutrition-binding neurons with blood vessels)

2-Microglia, protection( phagocytosis of bacteria …)

3-Oligodendrocyte ,(produce myelin )

4-Ependymal cells-lining ventricles of the brain and central canal of spinal cord

Neuroglial cells in Peripheral Nervous system: 1-Satellite cells (supporting ganglion cells)

2-Schwan cells (produce myelin in peripheral nerves).

multipolar neuron in

autonomic ganglia

Peripheral nervous System: Comprise of nervous tissues outside

brain and spinal cord ; small aggregates of nerve cells called peripheral ganglia and

nerves . A peripheral nerve is a bundle of nerve fibers, each has

a connective tissue coverings from deep to superficial is:

Endoneurium wraps each single nerve fiber(axon).

Perineurium: Wraps groups of fibers forming fascicles.

Epineurium: Wraps groups of fascicles to form larger

nerves or nerve trunk.

Peripheral Nerve Trunk

Peripheral Nerve

Discussion

with students

Red =Epineurium

Black arrow=Perineurium

Blue star = nerve fascicle Containing numerous myelinated

fibers-axons covered by EndoneuriumNode of Ranvier high power

low power

Node of Ranvier X 400

Pseudounipolar Neurons

in peripheral ganglia

multipolar neuron in

autonomic ganglia

stellate star shaped neurons from

Gray matter of spinal cord

Summary Features of The Nervous Tissues with student participation:

1-Excitable tissues and fast acting control system.

2-Composed of neurons with their processes(axon &dendrites) and supporting glia cells.

3-It triggers contraction of muscle and gland secretion

4-It shares muscle in one feature and that is (irritability) excitability

5-It has another unique feature which is conductivity.

6-It senses stimuli and transmits signals from one part of the body to another

(internal stimuli).

7-It allows the body to respond to the environment (external stimuli).

8-No connective tissue within C N S, only in PNS(..?) and superficial aspects

of brain and spinal cord( the three layers of Meninges).

9-Neurons have no Centrioles (cannot divide). ??

10-Bundles of myelinated axons are called tracts in the CNS and nerves in the PNS.

11- Neurons, for survival , need a continuous supply of oxygen and glucose.

End of Nervous Tissue

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References:

Wheater's Functional Histology by Barbara Young Elsevier 6TH ed. Churchill

Livingstone.edinburgh

Junqueira's Basic Histology: Text and Atlas, 13th ed / McGraw- Hill.

HISTOLOGY A TEXT AND ATLAS by Ross & Pawlina / Lippincott Williams and

Wilkins ,Fifth edition.

Textbook of Histology by Leslie Gartner pub: Elsevier 4th EDITION

Histology Books, Ebooks & Journals | US Elsevier Health

www.us.elsevierhealth.com/medicine/histology

Normal histology, with special reference to the ... - Internet Archive

https://archive.org/details/normalhistologyw00pier. Internet Archive.

Di Fiores Atlas of Histology with functional correlations. 12th ed. Wolters Kluwer/

Lippincott,& Wilkins Int.

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