1. NERVOUS SYSTEM(NS)
Dr M Idris Siddiqui
divided into
central nervous system (CNS)
&
peripheral nervous system(PNS).

2. Nervous System…
 The nervous system regulates most body
systems using direct connections called
nerves. It enables you to sense and respond to
stimuli
 The basic function of nervous system are:
1. Receive sensory input internal or external
2. Integrate the input
3. Responding to internal and external
stimuli

3. Basic Functions of the Nervous System
1. Sensation
 Monitors changes/events occurring in and outside the
body. Such changes are known as stimuli and the cells
that monitor them are receptors.
1. Integration
 The parallel processing and interpretation of sensory
information to determine the appropriate response
1. Reaction
 Motor output.
• The activation of muscles or glands (typically via the release
of neurotransmitters (NTs))

4. SENSATIONS
CNS
Integrates
elaborates
Associates
Muscles
&
Glands
Sensory nerve fibres Motor nerve fibres

5. FUNCTIONAL
A) Afferent division=sensory
Efferent division=motor
B)Somatic division:
concerned with skeletal muscles
Autonomic division:
concerned with viscera

6. CNS: (neuraxis)
1) is part of NS which is protected by
bone. i.e. brain & spinal cord,both are
connected at the level of foramen magnum
2) is part of NS which is covered by
three meninges(dura, arachnoid,pia)
Funtions of CNS:
It receives different sensations, associates, integrates, &
elaborates, selects motor neurons which send motor orders to
proper muscles or glands to perform a proper response.
PNS:

8. Protection to the Brain
Nervous tissue is soft and delicate, and
the irreplaceable neurons can be injured
or destroyed by even slight pressure
The brain is protected from injury by…
The skull
Surrounding membranes called meninges
A watery cushion of cerebrospinal fluid
The blood-brain barrier

9. Organization of the
Nervous System
 2 big initial divisions:
1. Central Nervous System
 The brain + the spinal cord
• The center of integration and control
1. Peripheral Nervous System
 The nervous system outside of the
brain and spinal cord
 Consists of:
• 31 Spinal nerves
 Carry info to and from the spinal
cord
• 12 Cranial nerves
 Carry info to and from the brain

10. Conclusion

11. Peripheral Nervous System
Responsible for communication btwn the CNS
and the rest of the body.
Can be divided into:
Sensory Division
Afferent division
• Conducts impulses from receptors to the CNS
• Informs the CNS of the state of the body interior and exterior
• Sensory nerve fibers can be somatic (from skin, skeletal
muscles or joints) or visceral (from organs w/i the ventral body
cavity)
Motor Division
Efferent division
• Conducts impulses from CNS to effectors (muscles/glands)
• Motor nerve fibers

12. Motor Efferent Division
Can be divided further:
Somatic nervous system
VOLUNTARY (generally)
Somatic nerve fibers that conduct impulses from the
CNS to skeletal muscles
Autonomic nervous system
INVOLUNTARY (generally)
Conducts impulses from the CNS to smooth muscle,
cardiac muscle, and glands.

13. Autonomic Nervous System
Can be divided into:
 Sympathetic Nervous
System
“Fight or Flight”
 Parasympathetic
Nervous System
“Rest and Digest”
These 2 systems are antagonistic.
Typically, we balance these 2 to keep ourselves in a
state of dynamic balance.
We’ll go further into the difference btwn these 2
later!

14.  The nervous system is composed of the
following organs and tissues:
1. Brain
2. Spinal cord
3. Sense organs (eyes, ears, etc.)
4. nerves

15. Embryonic Development
The spinal cord
develops from the
caudal portion of the
embryonic neural
tube
By the end of the
6th week each side
of the developing
cord has two
clusters of
neuroblasts that
have migrated
outwarded from the

16. Embryonic Development
The two clusters are
the dorsal alar plate
and a ventral basal
plate
Alar plate neurons
become
interneurons
The basal plate
neurons become
motor neurons that
sprout axons that
grow out to the

17. Embryonic Development
Axons that emerge
from alar plate cells
form the external
white matter of the
cord by growing
outward along the
length of the CNS
The alar plates
expand dorsally and
the basal plates
expand vertically to
become the H-
shaped mass of
gray matter

18. Embryonic Development
Neural crest cells
that come to lie
alongside the cord
form the dorsal root
ganglia containing
sensory nerve cell
bodies, which send
their axons to the
dorsal aspect of the
brain
Neural crest cells

19. Embryonic Development
Neural crest cells
that come to lie
alongside the cord
form the dorsal root
ganglia containing
sensory nerve cell
bodies, which send
their axons to the
dorsal aspect of the
brain
Neural crest cells

21. NERVOUS TISSUES
These are
Neurons (original nerve
cells) and
Neuroglia (supporting
tissue)

22. Nervous Tissue
 Highly cellular
 How does this compare
to the other 3 tissue
types?
 2 cell types
1. Neurons
 Functional, signal
conducting cells
1. Neuroglia
 Supporting cells
1.
2.

23. Myelination in the CNS
Myelination in the PNS

24. NEURONS:
Def:Anatomical,physiological,embryological unit of nervous system
Classification
A-Anatomical
a-According to polarity
1.Unipolar/pseudounipolar(T-shaped)
2.Bipolar-spindle shaped
3.Multipolar(single axon-multiple dendrites)
b-According to relative length of axons & dendrites(size)
1.Golgi type 1, long axons may be 1m long, form tracts
2.Golgi type 11,star shaped,found in cerebral & cerebellar cortex
B-Functional
a-Sensory neurons.1.Primary sensory neurons. Outside CNS
2.Secondary neurons. Lie in CNS
3.Tertiary neurons.Lie in thalamus.
b-Motor neurons.
a. Upper motor neurons i.e. corticoneuclear & corticospinal
b.Lower motor neurons i.e. cell bodies lie in brain stem/spinal cord
c-Autonomic neurons
a. Preganglionic neurons in brain & spinal cord
b. Postganglionic neurons outside CNS.

25. Neuron
Nervous tissue is composed of 2 main cell
types: neuron & glial cells
The neuron is the functional unit of the nervous
system
All neurons have three parts:
Dendrites receive information from another cell
and transmit the message to the cell body
cell body contains the nucleus, mitochondria
and other organelles typical of eukaryotic cells
Axon conducts messages away from the cell
body

26. NeuronsThe functional and structural unit
of the nervous system
Specialized to conduct information from one part of the
body to another
There are many, many different types of neurons but most
have certain structural and functional characteristics in
common:
- Cell body (soma)
- One or more
specialized, slender
processes
(axons/dendrites)
- An input region
(dendrites/soma)
- A conducting
component (axon)
- A secretory (output)
region (axon terminal)

28. Three types of neurons :
Sensory neurons -long dendrite, short
axon and carry messages from sensory
receptors to the central nervous system
Motor neuron -long axon, short dendrite
and transmit messages from the central
nervous system to the muscles (or to
glands)
Interneuron -found only in the central
nervous system where they connect neuron
to neuron

29. NEUROGLIA
5 times numerous than neurons. These are
non neural ,nonexitable cells that form a major
components of nervous tissues,supporting,
insulating, nourishing the neurons.
IN CNS-
oligodandrocytes,astrocytes,ependymal cells,&
microglia
IN PNS- Stellite cells surround neurons in
spinal cord & autonomic ganglia
 Neurolemma(Schwann cells)

31. Neuroglia
 Outnumber neurons by about
10 to 1 (the guy on the right had
an inordinate amount of them).
 6 types of supporting cells
 4 are found in the CNS:
1. Astrocytes
 Star-shaped, abundant, and
versatile
 Guide the migration of
developing neurons
 Act as K+ and NT buffers
 Involved in the formation of the
blood brain barrier
 Function in nutrient transfer

32. Neuroglia
2. Microglia
 Specialized immune cells that act
as the macrophages of the CNS
 Why is it important for the CNS to
have its own army of immune
cells?
2. Ependymal Cells
 Low columnar epithelial-esque
cells that line the ventricles of the
brain and the central canal of the
spinal cord
 Some are ciliated which
facilitates the movement of
cerebrospinal fluid

33. Neuroglia
4. Oligodendrocytes
 Produce the
myelin
sheath
which
provides the
electrical
insulation for
certain
neurons in
the CNS

34. • 2 types of glia in the
PNS
1. Satellite cells
• Surround clusters of
neuronal cell bodies in the
PNS
• Unknown function
2. Schwann cells
• Form myelin sheaths
around the larger nerve
fibers in the PNS.
• Vital to neuronal
regeneration
Neuroglia

35. Developmental Aspects of CNS
Fetal alcohol syndrome
Cerebral palsy
Anencephaly (without brain)
Spina bifida (forked spine)

36. Nervous Tissue: Support CellsNervous Tissue: Support Cells
Slide 7.7aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Oligodendrocytes
•Produce myelin
sheath around
nerve fibers in the
central nervous
system
Figure 7.3d

37. Nervous Tissue: Support CellsNervous Tissue: Support Cells
Slide 7.7bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Satellite cells
•Protect neuron cell bodies
• Schwann cells
•Form myelin sheath in the peripheral
nervous system
Figure 7.3e

38. Schwann cells
Serve as supportive, nutritive, and service
facilities for neurons
The gap between schwann cells is known as the
node of Ranvier (serve as point along the
neuron for generating a signal)
Signal jumping from node to node travel
hundreds of times faster than signals traveling
along the surface of the axon

40. Nervous Tissue: Support CellsNervous Tissue: Support Cells
Slide 7.6Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Microglia
• Spider-like phagocytes
• Dispose of debris
• Ependymal cells
• Line cavities of the
brain and spinal cord
• Circulate
cerebrospinal
fluid
Figure 7.3b, c

41. Potential problems with neuroglia
(support) cells
Similar to nerve cells, but can’t send
signals
Never lose the ability to reproduce (divide)
Neuroglia that keep growing without
stopping form gliomas

42. The Nerve message
An unequal distribution of ions and electrical
charges between the two sides of the membrane.
Outside-positive , inside-negative charge.
Passage of ions across the cell membrane passed
the electrical charge along the cell.
The action potential begins at one spot on the
membrane, but spread to adjacent area of the
membrane, propagating the message along the
length of the cell membrane.

43. Synapse
sThe junction between a nerve cell and another cell is
called a synapse
The space between two cell is known as the synaptic
cleft
To cross the synaptic cleft requires the action of
neurotransmitters
Neurotransmitters are stored in small synaptic vesicles
clustered at the tip of the axon
Arrival of the action potential causes some of the
vesicles to move to the end of the axon and discharge
their content into the synaptic cleft
Bind to receptor molecules on the next cell, prompting

45.  Nervous system can be divided into two
system;
1. Central Nervous System (CNS)
 Brain
 Spinal cord
2. Peripheral Nervous System (PNS)
 The somatic nervous system
 The autonomic nervous system
• Sympathetic systems
• Parasympathetic systems

46. A) CNS: Brain
 main control center - homeostasis, thoughts,
emotions.
1. Cerebrum-conscious activity, memory, language
and senses are processed here
2. Cerebellum-balance, posture, and coordination
3. Brain stem which has the following parts and
functions:
 Medulla oblongata -controls involuntary
activities
 Pon -pathway connecting upper functions of the
brain with the rest of the spinal cord
 Midbrain -location of:
 Thalamus-receives all sensory information
 Hypothalmus-the seat of homeostasis and
control over the endocrine system.

48. connects the brain to the rest of the body,
sending and receiving messages.
Runs along the dorsal side of the body and
links the body to the rest of the body
Vertebrates have their spinal cord encased in
a series of (usually) bony vertebrae that
comprise the vertebral column
The gray matter -cells bodies and dendrites
The white matter -bundles of interneuronal
A) CNS: Spinal cord

49. B)PNS:Somatic Nervous
System
Consists of bundles of sensory and motor
neurons relaying information between the
central nervous system and muscles or
sensory organs.

50. regulates unconscious bodily functions such as:
movement of food through your intestines
secretion of hormones and digestive enzymes
breathing and heart rate
reflexes
Have 2 subsystems:
Sympathetic
Parasympathetic
B)PNS:Autonomic Nervous
System

51. Types of Nerve Fibers
1. Group A
 Axons of the somatic sensory neurons and motor neurons
serving the skin, skeletal muscles, and joints.
 Large diameters and thick myelin sheaths.
 How does this influence their AP conduction?
1. Group B
 Type B are lightly myelinated and of intermediate diameter.
1. Group C
 Type C are unmyelinated and have the smallest diameter.
 Autonomic nervous system fibers serving the visceral organs,
visceral sensory fibers, and small somatic sensory fibers are
Type B and Type C fibers.

52. 1. The sympathetic nervous system
 It produces heightened alertness --
increase in heart rate, blood flow is
directed to arms and legs and away from
the body core and digestion.
2. The parasympathetic
 reduces heart rate and increases blood to
internal organs such as digestion.

53. Nervous Tissue: NeuronsNervous Tissue: Neurons
Slide 7.8Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Neurons = nerve cells
•Cells specialized to transmit messages
•Major regions of neurons
•Cell body – nucleus and metabolic center
of the cell
•Processes – fibers that extend from the
cell body

54. Neuron AnatomyNeuron Anatomy
Slide 7.9aCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cell body
•Nissl
substance –
specialized
rough
endoplasmic
reticulum
•Neurofibrils –
intermediate
cytoskeleton
that maintains
cell shape Figure 7.4a

55. Neuron AnatomyNeuron Anatomy
Slide 7.9bCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cell body
•Nucleus
•Large
nucleolus
Figure 7.4a

56. Neuron AnatomyNeuron Anatomy
Slide 7.10Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Extensions
outside the cell
body
• Dendrites –
conduct
impulses toward
the cell body
• Axons – conduct
impulses away
from the cell
body
Figure 7.4a

57. Axons and Nerve ImpulsesAxons and Nerve Impulses
Slide 7.11Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• 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

58. Neuron Cell Body LocationNeuron Cell Body Location
Slide 7.13Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most are found in the central nervous
system
•Gray matter – cell bodies and unmylenated
fibers
•Nuclei – clusters of cell bodies within the
white matter of the central nervous system
• Ganglia – collections of cell bodies
outside the central nervous system

59. Neurons

60. Two Parts
Central (CNS)
Peripheral (PNS)

61. http://inside.salve.edu/walsh/cns_pns.jpg

62. Central Nervous System
Brain
Spinal cord

63. The Brain
Coordinates body activities
Made up of approximately 100 billion
neurons
Divided into three major parts-
the cerebrum
the cerebellum
the brain stem.

65. Cerebrum
Largest part of the brain
Thinking
Memory is stored
Movements are controlled
Impulses from the senses are interpreted.

67. Cerebellum
Interprets stimuli from eyes, ears, muscles
Controls voluntary muscle movements
Maintains muscle tone
Helps maintain balance

69. Brain Stem
Connects brain to spinal cord
Made up of
The midbrain,
The pons,
Act as pathways connecting various parts of the
brain with each other
Medulla
controls involuntary actions

71. The Spinal Cord
Extension of the brain stem
Bundles of neurons that carry impulses
from all parts of the body to the brain and
from the brain to all parts of your body
Extension of the brain stem . It is made up of bundles of
neurons that carry impulses from all parts of the body to the
brain and from the brain to all parts of your body

72. Research
Visit the
Glencoe
Science
Web site at
tx.science.glencoe.com
for more
information
about the
nervous
system.
Make a
brochure
outlining
recent
medical
advances.
The
Peripheral
Nervous
System
Your brain
and spinal
cord are
connected
to the rest
of your
body by the
peripheral
nervous
system.
The PNS is
made up of
12 pairs of
nerves from
your brain
called
cranial
nerves, and
31 pairs
from your
spinal cord
called
spinal
nerves.
Spinal
nerves are
made up of
bundles of
sensory
and motor
neurons
bound
together by
connective
tissue. For
this reason,
a single
spinal
nerve can
have
impulses
going to
and from
the brain at
the same
time. Some
nerves
contain
only
sensory
neurons,
and some
contain
only motor
neurons,
but most
nerves
contain
both types
of neurons.
Somatic
and
Autonomic
Systems
The
peripheral
nervous
system has
two major
divisions.
The
somatic
system
controls
voluntary
actions. It
is made up
of the
cranial and
spinal
nerves that
go from the
central
nervous
system to
your
skeletal
muscles.
The
autonomic
system
controls
involuntary
actions-
those not
under
conscious
control-
such as
your heart
rate,
breathing,
digestion,
and
glandular
functions.
These two
divisions,
along with
the central
nervous
system,
make up
your body's
nervous
system.

73. Peripheral Nervous System
Two divisions
Somatic
Autonomic

74. Peripheral Nervous System
Connects body to brain & spinal cord
12 pairs of nerves from your brain (cranial
nerves)
31 pairs from your spinal cord (spinal
nerves)
Bundles of sensory and motor neurons held
together by connective tissue

75. Peripheral nervous system
PNS
All neural tissue outside CNS constitute PNS
 It is composed of
a)Nerves: Bundles of axons in NS constitute nerves, depending
on location such a bundle may be called as rootlet, root,
trunk,division,cord, ramus, branch.
A network of interjoining of nerves called as plexus.
1)Cranial:motor(3,4,6,11,12),sensory(1,2,8),&mixed(5,7,9,10)
2)Spinal: mixed(31)
b)Nerve endings__sensory=receptors
Motor=effectors
c)Nerve ganglia 1)sensory=dorsal or sensory root ganglia
2)motor(autonomic)sympathetic&
parasympathetic

76. Functions of PNS
It receives sensations from receptors by
way of sensory nerve fibres.It transmits
these sensations to CNS
It also carries motor orders from CNS to
muscles & glands (effectors) by means of
motor nerve fibres.

79. Somatic Nervous System
Controls voluntary actions
Made up of the cranial and spinal nerves
that go from the central nervous system to
your skeletal muscles

80. Autonomic Nervous System
Controls involuntary actions-those not
under conscious control-such as your
heart rate, breathing, digestion, and
glandular functions

81. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/autonomic.gif

82. Reflexes
Involuntary, automatic response to a
stimulus
Involves a simple nerve pathway called a
reflex arc