The nervous system is composed of neurons and neuroglia. It can be divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which includes nerves outside the CNS. The CNS is further divided structurally into the brain and spinal cord. The PNS is divided functionally into sensory nerves, which carry information to the CNS, and motor nerves, which carry signals away from the CNS to muscles and glands. Within the nervous system there are three main cell types - neurons, which transmit signals; neuroglia, which provide nutrients and insulation; and myelin, a fatty sheath that surrounds neurons and enables faster signal transmission.

1. Nervous System
MsShama Praveen

2. The Nervous
System
• The nervous system coordinates all
body functions, enabling a person
to adapt changes in internal and
external environment
• The nervous system is composed
mainly of the nerve cells (neurons)
and supporting cells (neuroglia)

3. Structural Classification of the
Nervous System
∙ Central nervous system (CNS)
∙ Brain
∙ Spinal cord
∙ Peripheral nervous system (PNS)
∙ Nerve outside the brain and spinal cord

4. Functional Classification of the
Peripheral Nervous System
∙ Sensory (afferent) division
∙ Nerve fibers that carry information to the
central nervous system

5. Functional Classification of the
Peripheral Nervous System
∙ Motor (efferent) division
∙ Nerve fibers that carry impulses away from
the central nervous system

6. Functional Classification of the
Peripheral Nervous System
∙ Motor (efferent) division
∙ Two subdivisions
∙ Somatic nervous system = voluntary
∙ Autonomic nervous system = involuntary

7. Organization of the Nervous
System
Slide 7.4

8. Nervous Tissue (Neuron)

10. The basic unit of
nervous tissue is
the cell called the
Neuron.
Neuro
n

11. Neuro
ns
consi
st
Nucleus
ofa
main
part
called
the cell
body,
whichcontains the
nucleus and various
Cell Body
Nucleol
us
• 4 to 100 micrometers in
diameter
• (Soma)

12. Neurons also
contain cell body
“extensions” called
processes, which
carry impulses to
and from the cell
body.
axo
n
dendrit
es
Two different
types of processes
can come from the
cell body. The first is
called the dendrite
and the other the
axon.

13. Dendrites, also
called afferent
processes, carry
impulses TOWARDS
the cell body.
Axons, also called
efferent processes,
carry impulses AWAY
from the cell body.

14. ▪ Some axons are enveloped by
Schwan Cells which provide
structural and metabolic
support.
▪ These are classified on Basis
of Presence/Absence of
Myeline Sheath.
-> Myelinated
-> Non-Myelinated

15. Axons and Nerve Impulses
∙ Axons end in axonal terminals
∙ Axonal terminals contain vesicles with
neurotransmitters
∙ Axonal terminals are separated from
the next neuron by a gap
∙ Synaptic cleft – gap between adjacent
neurons
∙ Synapse – junction between nerves

17. Myelin
• Myelin is a
fatty covering
which
envelops
many axons
and permits
action
potentials to
be propagated
Myeli
n

18. Nodes of Ranvier
Nodes of Ranvier are short
fragments of unmyelinated
segments of the axon,
which are found periodically
in between the cells of the
myelin sheath.
• These nodes are areas
where the action potential
is amplified using a high
density of sodium (Na+)
ions and is subsequently
passed along the axon.
• The points between
segments of myelin are
called nodes of Ranvier.
Nodes
of
Ranvier

19. Classification of Neurons

20. There are actually three different
types of neurons in the human body.
They can be
classified either according totheir
function or structure:
Functional Classification:
Sensory Neurons
Motor Neurons
Interneurons (Association Neurons)
Structural Classification:
1. Unipolar Neurons
2. Bipolar Neurons
3. Multipolar Neurons

21. Structural Classification of Neurons
∙ Multipolar neurons – many extensions
from the cell body

22. Structural Classification of Neurons
∙ Bipolar neurons – one axon and one
dendrite

23. Structural Classification of Neurons
∙ Unipolar neurons – have a short single
process leaving the cell body

25. Sensory
neurons or
Afferent neurons–
These
neuro
ns
transmit impulses from the periphery of the body
to the central nervous system.
They are described as unipolar meaning they
have only a single process.
• This process is actually an axon which branches
into two parts and spread in opposite directions.
• In this way, one branch acts as the dendrite, while
the other acts as the axon.

26. Motor neurons or Efferent neurons – These
neurons carry impulses AWAY from the cell body
and thus the central nervous system to muscles,
gland, or some other “effector” to produce a certain
action.
This action can be the contraction of a muscle or
the secretion of a gland.
Motor neurons are classified as multipolar,
which means they have numerous branching
dendrites leading into the cell body and a single
long axon leading out. Most of the neurons in the
spinal cord and many of those in the brain are
motor neurons.

28. Interneurons or Association neurons- This type
of neuron is restricted to the central nervous
system. They are also called connector neurons.
These neurons act as bridges between sensory
and motor neurons or relay impulses to various
functional centers of the brain or spinal cord.
They resemble motor neurons in that they have
one axon with multiple dendrites, however, their
function is much different.

29. Sensory Neuron
Interneur
on
Motor
Neuron

30. Neuroglia

32. Neurogli
a
• Neuroglia do not
generate or
conduct nerve
impulses.
• However, unlike
other cells can
regenerate if
injured.

33. • Astrocytes -
Provide energy and
other metabolic needs of
neurons as well as
giving nervous tissue
structural support.
• Abundant, star-shaped
cell
• Brace neuron
• Form barrier between
capillaries and neurons
• Control the chemical
environment of the
brain (CNS)

34. Microglia - Phagocytic cells, similar to
macrophages, that perform a housekeeping
function by removing dead cellular material
and bacteria from the CNS.
Spider-like

35. ∙ Ependymal Cells - Cells that line the
cerebral spinal fluid (CSF) containing
cavities of the brain - the ventricles.
Line cavities of the
brain and spinal cord
∙ Circulate cerebrospinal fluid

36. Oligodendrocytes - Produce myelin sheath
around nerve fibers in the central nervous system

37. Support Cells of the PNS
∙ Satellite cells
∙ Protect neuron cell bodies
∙ Schwann cells
∙ Form myelin sheath in the peripheral
nervous system
Figure 7.3e

38. Thank you