This document discusses nerve cells (neurons), including their structure, classification, function, relevance in dentistry, major neurological disorders, and advances in management. It defines neurons, notes their discovery by Santiago Ramon y Cajal, and provides interesting facts about neurons in the human body. It describes the main parts of neurons including the soma, dendrites, axon, and synapses. It also discusses myelinated and unmyelinated neurons, classifications of neurons, how they transmit signals, and their role in sensing pain and sensitivity in teeth. Major neurological disorders like Alzheimer's, Parkinson's, and myasthenia gravis are summarized. Recent research on using nanotechnology and transcription factors to promote nerve regeneration is also mentioned

1. NERVE CELLS
Dr.Milcah Jovin
Dept.Of oral pathology

2. Introduction
Interesting facts
Structure
Classification
Function
Relevance in dentistry and clinical application
Major neurologic disorders
Advances in nerve management
CONTENTS

3. Introduction
Definition
A nerve cell (neuron) is an electrically excitable cell that
processes and transmits information through electrical and
chemical signals
History
 The credit for identifying the role of nerve cells
Spanish anatomist – Santiago Ramon y Cajal in 19th
century
 The “Double Impregnation model” using silver staining method
developed by him is still used to identify the structure of neurons

4. Interesting facts about Nerve cells
 The human brain has approximately 100 billion neurons .
Stars in the Milky Way
 If we lined up all the neurons in our body it would come to around
600miles.
 Neurons are the oldest and longest cells in the body. In fact, you
have fewer neurons when you are old compared to when you are
young .
 Rate of neuron growth during foetal development in utero = 250,000
neurons/minute .
 Length of giraffe primary afferent axon (from neck to toe) = 15 feet.
 An artificial neuron is a mathematical function conceived as
a model of biological neurons.

5. Structure of neuron-Diagram

6. Structure
 Soma /Perikaryon is the body of the neuron -produce
proteins
 Neuronal membrane barrier to enclose the cytoplasm
inside the neuron
 Dendrites (receptive zone) convey the electrical impulses
towards the cell body.

7.  Axon
-Finer, cable-like ,cytoplasmic projection
-The axon carries nerve signals away from the soma
 Axon terminal
-contains synapses
-neurotransmitter chemicals are released to communicate with
target neurons.

8. Axon hillock
-axon is joined to the cell.
-electrical firing (action potential).

9. UNMYLINATED NERVE CELLS &
MYLINATED NERVE CELLS
(SALTATORY CONDUCTION)

10. MYELINATED AND NON-
MYELINATED AXONS
 Main purpose
- increase the speed
 White, insulating sheath on the axon
 Deposited by schwann cells
MOVEMENT
-unmyelinated fibers-continuously as waves
-myelinated fibers- "hop" or propagate
by saltatory conduction
NODE OF RANVIER
-periodic gap in the insulating mylien
sheath on the axon of certain neurons
-facilitate the rapid conduction of nerve impulses.
-gaps are rich in ion channels ( sodium and chloride, )

11. Nerve - Primary structure of PNS

12. Classifications
Structural Functional
Neurotransmitter
production
1)Unipolar
2)Pseudounipolar
3)Bipolar
4)Multipolar
1)Afferent/sensory
2)Efferent/motor
3)Interneurones
1)Cholinergic
2)GABAergic
3) Glutamatergic
4)Dopaminergic
5) Serotonergic
Classifications
1)Unipolar
2)Pseudounipolar
3)Bipolar
4)Multipolar

14. Functioning

15. Functioning
 Neurons are nerve cells that originate, process, transmit,
and receive nerve impulses.
 Nerve impulses electrically chemical
messengers (neurotransmitters across a tiny gap
synapse) target cell.

16. Functioning
Synapses
 In synapses and junctions, information is
transmitted in the form of chemical messengers
called neurotransmitters.
 Transmit either excitatory or inhibitory signal.
 Receptors that detect the neurotransmitters in
the synaptic cleft.

17. SIGNAL TRANSMISSION
WITHIN NERVE CELLS
•Voltage differences (ie; Potentials) that exist between
inside and the outside of the cell.
• Ions enter and exit the cell through specific protein channels in
the cell’s membrane.
• Channels “open” or “close” in response to neurotransmitters or to
changes in the cell’s membrane potential.

18. •Redistribution of electric charge may alter the voltage difference
across the membrane.
•Decrease in the voltage difference is called depolarization.
•If depolarization exceds a certain threshold, an impulse
(i.e., action potential) will travel along the neuron.
•The generation of an action potential is sometimes
referred to as “firing

19. Relevance in Dentistry
 The plexus of Raschkow monitors painful sensations.
 There are two types
A-fibers -conduct rapid and sharp pain sensations
-Mylinated
-A delta type-located in the periphery of the pulp
C-fibers -dull aching pain
-thinner and unmyelinated.
-terminate in the pulp tissue proper, either as
free nerve endings or as branches around
blood vessels.

20. CLINICAL RELAVENCE
 As gums recede, dentin is exposed.
 When teeth make contact with something hot, cold or
sweet, sensations are carried directly to the nerves,
causing painful tooth sensitivity.
 DESENSITIZING TOOTH PASTES- it contains an
ingredients such as potassium nitrate or strontium
chloride, which block pain signals to the nerve of the
tooth by stopping up the tiny tunnels in your teeth, which
go to the nerve.(SENSODYNE,COLGATE SENSITIVE)

21. MAJOR NEUROLOGICAL DISORDERS
Charcot–Marie–Tooth disease
 Heterogeneous inherited disorder of nerves
 Loss of muscle tissue and touch sensation
 Presently incurable
 One of the most common inherited
neurological disorders
 37 in 100,000 affected
 Famous persons - George J. Donahue –
World famous poet

22. Alzheimer's disease
 Neurodegenerative disease
 Declining activities of daily living
and neuropsychiatric symptoms or behavioural
changes
 Early symptom is loss of short-term memory
(amnesia)
 Famous personality with this –
Ronald Reagan

23. Parkinson's disease
 Degenerative disorder of the central nervous system
- impairs the sufferer's motor skills and speech.
 Characterized
-muscle rigidity
-tremor
-slowing of physical movement (bradykinesia)
-in extreme cases a loss of physical movement
 Chronic and progressive.
 Famous persons with this – Pope John Paul II And
Mohammed Ali (Boxer)

24. Myasthenia gravis
 Neuromuscular
 Symptoms
 fluctuating muscle weakness
 fatigability during simple activities
 Treatment:
Immunosuppressants, cholinesterace inhibitors and
in selected cases, thymectomy
 Famous personalities with myasthenia gravis-
Amitabh Bachan

25. Advances in nerve cells management
 Nerve damage from neurodegenerative disease and spinal
cord injury has largely been considered irreversible, but
Dartmouth researchers report progress in the effort to
synthesize rare natural products that promote
regeneration and growth of injured nerve cells
 The use of nanotechnology to improve the design of nerve
conduits and to enhance nerve regeneration.

26. CARBON NANOTUBES
Consisting of biological tissue and synthetic material -- planned
to re-establish connections between nerve cells, for instance at
spinal level, lost on account of lesions or trauma.
(This is the result of a piece of research published on the
scientific journal Nanomedicine: Nanotechnology, Biology, and
Medicine conducted )
TRANSCRIPTION FACTOR
Help certain neurons regenerate, while simultaneously killing
others.
Unravelling exactly which signals can help or hinder axon
regeneration may eventually lead to new and precise
treatment strategies for restoring vision or repairing injury.
(In a new study published in Neuron, Bei, Michael Norsworthy in
Zhigang He's lab at Boston Children's Hospital and colleagues)