Neurons are specialized cells in the nervous system that transmit messages through an electrochemical process and are classified based on structure (bipolar, unipolar, multipolar) and function (sensory, motor, inter neurons). They consist of a cell body, dendrites, and axons, with axons often covered by a myelin sheath that enhances signal transmission speed. Neurons communicate by generating action potentials and releasing neurotransmitters at synapses to relay information to other neurons, muscles, or glands.

1. Structure of a neuron

2. STRUCTURE OF A NEURON

3. NEURON:
 The human body is made up of
trillions of cells. Cells of the nervous
system, called nerve cells or neurons.
 The human brain has approximately 100
billion neurons, more in the spinal cord,
peripheral nervous system and sensory
organs.
 These system’s basic building blocks,
are specialized to carry "messages"
through an electrochemical process.

4. • Neurons are similar to other cells
in the body because:
• Neurons are surrounded by a cell
membrane.
• Neurons have a nucleus that contains
genes.
• Neurons contain cytoplasm, mitochondria
and other organelles.
• Neurons carry out basic cellular processes
such as protein synthesis and energy
production.

5. Neurons are different from other cells in
the body because:
• Neurons have specialized extensions called
dendrites and axons. Dendrites bring
information to the cell body and axons take
information away from the cell body.
• Neurons communicate with each other
through an electrochemical process.
• Neurons contain some specialized structures
(for example, synapses) and chemicals (for
example, neurotransmitters).

6. Axon of
another
neuron
Cell
Body
Dendrit
es
Axo
n
Myeli
n
Sheat
h
Dendrites
of another
The Neuron
Node of
Ranvier
Synapt
ic
knobs

7. Dendrites are short branching processes from
the cell body
•Axon is a projection from the cell body and it is
few millimeters to one meter in length & covered
with the myelin sheath
•Myelin an insulating sheath Supports, insulates
& nourishes the axon and helps maintain
chemical balance
•Nodes of Ranvier allow passage of the
electrical signal through ion channels which
helps the transmission very fast.
The cell body is responsible for the nutrition.

8. Inside of a neuron!
*

9. CLASSIFICATION OF NEURONS

10. • On of the basis of structural
differences, neurons are classified
into the following three major
groups:
1. Bipolar Neurons
2. Unipolar Neurons
3. Multipolar Neurons

11. * Nafly Hussain *

12. • Most sensory neurons are bipolar e.g.
retinal cells
• Sensory cells of touch, pressure, pain are
special types of unipolar
• Multipolar: most common type in
vertebrates e.g., spinal motor neurons

13. Basis of functional differences,
neurons are classified as follows:
1. Sensory neurons
2. Inter neurons
3. Motor Neurons
*

14. • Sensory (or afferent) neurons: send
information from sensory receptors (e.g.,
in skin, eyes, nose, tongue, ears)
TOWARD the central nervous system.
• Motor (or efferent) neurons: send
information AWAY from the central nervous
system to muscles or glands.
• Inter neurons: send information BETWEEN
sensory neurons and motor neurons. Most
inter neurons are located in the central
nervous system.

15. • How Neurons Carry the Message:
• Only neurons are involved in transmission of
electrical signals.
• Within a nerve cell, message is an electrical
signal = action potential
-membrane depolarization creates the
movement of the action potential as a nerve
impulse
– rapid, all or none impulses
– in myelinated neurons, gaps at regular
intervals allow regeneration of the action
potential
• Between nerve cells the message is carried
chemically

16. Direction of neural impulse
DENDRITES -----> CELL *
BN
Oa
f
l
y
DH
Yu
s
s
a
(i
wn*
ith nucleus) -------> AXON

17. At the end of the axon, the axon terminus, is
the secretory region where the
neurotransmitters are released into the
synapse.
The function of the axon is to propagate the
neural impulse along its entire length. The
destination may be a muscle, a gland, or,
more commonly, the dendrites of another
neuron

18. MYELINATED NERVE FIBER

19. NERVE FIBER:
•Each nerve is formed by many bundles or
groups of nerve fibers.
•Each bundle of nerve fibers is called a fasiculus.
•The whole nerve is covered by a tubular
sheeth, called epineurieum.
•Each fasiculus is covered by perineurium.
•Each nerve fiber(axon) is covered by
endoneureium.

20. TYPES:
A.NON MYELINATED NERVE FIBER: i.e. not covered
by myelin sheeth
B.MYELINATED NERVE FIBER covered by myelin
sheeth
FUNCTION OF MYELIN SHEETH:
1.Faster conduction
2.Insulating capacity i.e. myelin sheeth restricts
the nerve impulse within single nerve fiber and
prevents the stimulation of neighboring nerve
fiber.