Seminar Histology of Nervous System by Nahla

Histology of Nervous system

1. HISTOLOGY OF
NERVOUS SYSTEM
By Ahmed Quthb

2. TABLE OF CONTENTS
Introduction to Nervous Tissue
Classification of Nervous Cells & Neurons
Supporting Structures in Nervous System
Cell Body of Neuron: Dendrites & Axon
Nerves: Peripheral and Optic
Ganglia: Spinal and Sympathetic
Clinical Integration
01
02
03
04
05
06
07

3. INTRODUCTION
01

4. Nervous tissue or Neural tissue
The interconnected network
of specialized cells known as
neurons, which are held up
by neuroglial cells, makes
up the nervous tissue.

The human body has
around 10 million neurons.
After receiving inputs,
the neurons carry them to
the central nervous system
CNS, where they are
processed and combined
to cause the effector organs
to react as intended.

5. CLASSIFICATION
02

6. CLASSIFICATION OF
NERVOUS SYSTEM
NERVOUS
SYSTEM
CENTRAL
NERVOUS
SYSTEM
PERIPHERAL
NERVOUS
SYSTEM

BRAIN
SPINAL
CORD
CEREBRO
SPINAL
NERVES
AUTONOMIC
NERVOUS
SYSTEM

7. Cranial nerves – 12 pairs
Spinal nerves – 31 pairs
Cerebrospinal Nerves
CLASSIFICATION OF NERVOUS SYSTEM
Autonomic Nervous System
Sympathetic nervous system and
Parasympathetic nervous system
CLASSIFICATION OF NEURONS
Morphological - based on the number of processes. .
1. Unipolar neuron – has single process.
2. Bipolar neuron – has two processes (axon & dendrite).
eg. spiral ganglion and bipolar cells in retina.
3. Multipolar neuron – has many processes (an axon & many dendrites).
e.g. autonomic ganglia and motor neurons.
4. Pseudounipolar neuron – has a single process that divides into an axon
(central process) and a dendrite (peripheral process). eg. cranial and spinal ganglia.
1.Sensory neuron – receives stimuli from receptors and
conducts impulses to CNS. e.g.sensory ganglia.
2.Motor neuron – conducts impulses from CNS to
effector organs (muscles). e.g. ventral horn cells.
3.Interneuron – connects sensory and motor neurons and
completes the functional circuit
Functional - based on the function performed

8. STRUCTURES IN NEURON
03

9. STRUCTURE OF A MULTIPOLAR NEURON
Cell body/ Soma/ Perikaryon Dendrites Axon

10. CELL BODY OF NEURON
04

11. It contains:
1.Nucleus
2.Nissl bodies
3.Golgi complex
4.Mitochondria
5.Neurofilaments
6.Melanin pigments
7.Lipofusion pigments
SITUATED IN THE GREY MATTER OF CNS
AND IN THE GANGLIA OF PNS

12. Highly branched, tapering processes of a neuron.
Covered by thorny spines- the sites of synaptic contact.
Receive stimuli from sensory cells and other neurons
– transmit them towards soma.
Sites of information input into neuron.
DENDRITES

13. Single, long, cylindrical process of a neuron.
Arises from a cone shaped portion of the cell body
called axon hillock, which is devoid of nissl bodies.
The cytoplasm of axon is called Axoplasm.
Plasma membrane is called Axolemma.
Terminates by dividing into many small branches,
Axon terminals, ending in small swellings – Terminal boutons.
AXON

14. Axon conducts impulses away from cell body
to axon terminals another neuron.
Bundles of axons are referred to as Nerve fibres.
Surrounded by myelin sheath which is derived from
schwann cells (PNS) or oligodendrocytes (CNS).
Neurons do not regenerate when the cell body is dead.
Myelin sheath - In PNS by schwann cells
and in CNS by oligodendrocytes.

15. NERVES
05

16. PERIPHERAL NERVE
It is made of bundles (fascicles) of nerve
fibers(axons). The bundles are held together by
connective tissue.
The cross section of nerve shows:
Epineurium – dense connective tissue sheath
surrounding the entire nerve.
Perineurium – connective tissue surrounding the
bundles of nerve fibers.
Endoneurium – surrounds individual nerve fibers

OPTIC NERVE
It differs from other peripheral nerves as:
It is surrounded by the Meninges of the brain.
Its nerve fibers are myelinated by Oligodendrocytes.
It is traversed by Central artery and Central vein.

17. IDENTIFICATION POINTS
FOR OPTIC NERVE

1.Central vessels of Retina
2.Bundles of myelinated Nerve fibers
3.Dura, Arachnoid and Pia maters surrounding the Nerve.

18. GANGLIA
06

19. SPINAL GANGLIA
●Spinal Ganglia is also known as Sensory Ganglia.
●Groups of Rounded Pseudounipolar neurons of
different size is found at the periphery.
●Neurons are separated by bundles of nerve fibers.
●It has Well defined satellite cells
●Centrally placed nuclei with prominent nucleolus.
●Epineurium forms the capsule of the ganglion
Identification point:
●Pseudounipolar neurons with centrally
placed nucleus found in groups.
●Well defined satellite cells.
SYMPATHETIC GANGLIA
●Small, angular multipolar neurons are seen scattered among the nerve
fibers.
●Poorly defined satellite cells and Eccentrically placed nucleus.
●Epineurium forms the capsule of the ganglion.
Identification point:
●Multipolar neurons with eccentrically placed nucleus found scattered.
●Poorly defined satellite cells

20. CLINICAL INTEGRATION
07

21. Nervous tissue can be affected by various clinical conditions that impact
the central and peripheral nervous systems. Here are some notable conditions:

Stroke: A vascular disorder that can cause either hemorrhage or ischemia, leading to tissue injury
in the brain or spinal cord. It is a common cause of disability and can result in long-term neurological deficits.

Meningitis: Inflammation of the membranes surrounding the brain and spinal cord, which can be caused
by viral or bacterial infections. Bacterial meningitis is particularly serious and can be life-threatening.

Multiple Sclerosis MS: An autoimmune disease where the fatty tissue (myelin) that surrounds the nerves
is destroyed, impairing the ability of the nerves to conduct electrical impulses to and from the brain.

Guillain-Barré Syndrome GBS: A rare neurological disorder where the bodyʼs immune system attacks
the peripheral nervous system, leading to muscle weakness and sometimes paralysis.

Parkinsonʼs Disease: A motor system disorder characterized by trembling, stiffness, and difficulty in
movement. It is caused by the loss of dopamine-producing neurons in the brain.

Epilepsy: A neurological disorder marked by recurrent seizures due to abnormal electrical activity in the brain.

Spinal Cord Injury: Damage to the spinal cord that can result from trauma or disease,
leading to loss of motor and sensory function below the level of injury.

Cerebral Aneurysm: A bulge or ballooning in a blood vessel in the brain, which can rupture and cause
a subarachnoid hemorrhage, leading to severe neurological damage.

22. In summary, nervous tissue is crucial for the bodyʼs ability to
process information, coordinate movements, and respond to stimuli,
making it a fundamental component of human physiology.

23. FEEL FREE TO ASK ANY
QUESTIONS YOU MAY HAVE.

24. THANK YOU