The nervous system can be divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and is responsible for integrating sensory information and coordinating motor commands. The PNS has two parts - the cerebrospinal part made up of cranial and spinal nerves, and the autonomic nervous system. There are two main cell types in the nervous system - neurons, which transmit signals, and neuroglia, which provide support and insulation. The autonomic nervous system has two divisions - the parasympathetic and sympathetic systems, which work in opposition to activate "rest and digest" and "fight or flight" responses respectively.

1. Nervous System
Presented by:
Mr.Manthan Kapadiya,
Assistant Professor
NCN,Visnagar

2. INTRODUCTION
Master system of the body
Functions:
1. Reception
2. Integration
3. Response

3. Subdivision of the nervous system
Anatomical subdivision:
1. Central nervous system(CNS)
brain and spinal cord
 Integration, processing and coordination of
sensory data and motor commands
 Higher functions
2. Peripheral nervous system (PNS)
a. Cerebrospinal nervous system
12 pairs of cranial nerves
31 pairs of spinal nerves
b. Autonomic nervous system

6. Cellular Organization of Neural
Tissue
Two cell types:
1. Neurons
“Excitable” cells
2. Neuroglia (mostly not excitable)
 Astrocytes
 Oligodendrocytes
 Microglial cells
 Ependymal cells
 Schwann cells
 Satellite cells

7. Neuron
 “Excitable” cells
 Structural & functional unit
of the nervous system.
 100 billion
Properties : excitability &
conductivity
Highly differentiated cell &
lost their power of division
EXCEPT olfactory

8. Typical Neuron Structure
Cell body or Soma or Perikaryon
Dendrites
Axon with axon hillock
Synaptic terminals

9. Cell body = Soma = Perikaryon

10. Classification of Neuron
1. According to numbers of
processes:
Unipolar neuron :
mesencephalic nucleus
Pseudounipolar neurons :
sensory & spinal ganglia
Bipolar neuron :
vestibulocochlear ganglia,
bipolar neuron of retina
Multipolar neuron : neurons in
cerebrum & cerebellum

11. 2. According to relative length of axons &
dendrites
• Golgi type I neuron : long axon
• Golgi type II neuron : short axon or
no axon

12. 3. Functional Classification
1. Sensory (Afferent)
1. Somatic
2. Visceral
2. Motor (Efferent)
A. .
1) Somatic
2) Visceral
B. .
1. Upper motor
2. Lower motor
C. .
1. Preganglionic
2. Postganglionic
3) Interneurons

13. 4. According to shape of the cell body
• Pyramidal cell
• Pyriform cell

14. Interesting facts
LONGEST NEURON :
 sensory neurons of S1 (1st sacral spinal nerve )
NEURON WITH MANY NEUTRITES BUT NO AXON
Amacrine Neurones Of Retina
NEURON WITH NO PROCESS
Para Neurons Of Adrenal Medulla

15. Neuron Organization
Divergence - One neuron synapses with several,
effectively "spreading the word".
Convergence - Several neurons synapse with a
single neuron, concentrating the input.
Serial processing - step-wise, sequential
Parallel processing - simultaneous processing of
different information

16. Neuroglia (Glue)
Structural & functional
support to the neuron.
5-10 times more than
neuron
All the neuroglia
develop from
neuroectoderm except
microglia (mesoderm)

17. Classification of neuroglia
Neuroglia in CNS
1. Astrocytes
2. Oligodendrocyte
3. Ependymal cells
4. Microglia
Neuroglia in PNS
1. Schwann cell or Neurolemmocytes
2. Satellite cells
Macroglia

18. Astrocytes: largest & most numerous
• Blood –brain barrier (BBB)
• Structural framework & repairs
• Regulation of ions, and nutrients,
to maintain metabolic
environment for the neuron
• Protoplasmic astrocyte
• Fibrous astrocyte

19. Blood Brain Barrier
Barrier
 Endothelium of Capillary
 Basement Membrane
 Foot process of Astrocyte
Areas in brain don’t have
BBB
 portion of hypothalamus
 pineal gland
 Pituitary
 Area Postrema
 choroid plexus

21. Oligodendrocyte
Smaller than astrocyte
Form myelin sheath around the fibers in CNS
Myelin improves the rate of impulse conduction by
acting as insulator.

22. Microglial cells
Smallest
Phagocytosis
 during infection or
injury
Derived from mesoderm

23. Ependymal cells
Lining of ventricles & central canal of
spinal cord
Some specialized to produce and monitor
CSF

24. Schwann Cells:(neurilemmocytes)
myelinated
Surround all peripheral
axons!
Responsible for myelination
of PNS
Involved in repair
mechanism after injury
Wallerian Degeneration
Neurilemma (Schwann sheath)

25. Schwann Cells in the PNS
Myelinated Nonmyelinated

26. Nerve fibres
Myelinated nerve fibers
Nonmyelinated nerve fibers
Myelination in CNS is by oligodendrocyte
Myelination in PNS is by Schwan cell

28. Satellite cells:
surround the autonomic and sensory
ganglia to provide support & nutrition

29. Functions of neuroglia
Structural & functional support to the neuron.
Blood- brain barrier.
Phagocytosis
Formation of myelin sheath.
Produce CSF.

30. Some Terminology
Collections of cell bodies –
ganglion in PNS
nucleus in CNS
Pseudoganglion
Bundles of axons –
tracts in CNS
nerves in PNS
“White matter” = myelinated axons, both nerves and tracts
“Gray matter” = non-myelinated material, dendrites, synapses
and cell bodies as well as nonmyelinated axons

31. Ganglion
Collections of nerve cell bodies
outside the CNS is called ganglion
1.cerebrospinal ganglia
2. autonomic ganglia
• sympathetic ganglia lie away from viscera they
supply
• Parasympathetic ganglia lie near the viscera
they supply

32. Central Nervous System

33. CNS
Brain
Spinal Cord

34. Subdivisions of Brain
1. Brain Stem
a. Midbrain
b. Pons
c. Medulla oblongata
2. Cerebellum
3. Diencephalon
Thalamus and
Hypothalamus
4. Cerebral Hemispheres

35. • Resides inside vertebral canal
• Extends to L1
• 31 segments, each associated
with a pair of dorsal root
ganglia
• Two enlargements
• Cervical and Lumbar
• Conus medullaris
• Cauda Equina
• Filum Terminale
Spinal cord:

36. Transverse Section
Dura covers both the dorsal and ventral roots.

37. Organization of Spinal Cord
Gray matter - interior horns
posterior - somatic and visceral sensory nuclei
anterior (and lateral) gray horns – somatic and visceral motor control
gray commissures - axons carrying information from side to side
White matter - tracts or columns
posterior white column -
anterior white column
lateral white column
anterior white commissure
functions
ascending tracts - sensory toward brain
descending tracts - motor from brain

38. Sectional anatomy of spinal cord
Outer white part; inner gray butterfly

39. Lumbar Puncture
(= Spinal Tap)
For clinical examination of CSF or
administration of radiopaque dyes,
drugs and anesthetics
However: mostly “epidurals” for
anesthetics
L3
S1

40. Reflexes
Fast, preprogrammed, inborn,
automatic responses
Occur in the CNS at the spinal
cord or brainstem levels
(cranial nerves)
May be either monosynaptic or
polysynaptic
All require
a. stimulus at receptor
b. sensory information relay
c. processing at CNS level
d. activation of motor
response
e. response of peripheral
effector

41. Withdrawal reflex

42. Stretch reflex (tendon jerks)

43. Ascending and Descending Tracts

44. Peripheral Nervous System

45. Nerve structure
•Axon
•Myelin sheath
•Neurilemmal sheath
• Similar to muscle terminology
• Epineurium
• Covers the nerve
• Perineurium
• Covers a fascicle
• Endoneurium
• Covers an axon

46. Blood & Nerve Supply
Vasa nervorum
 Vessels of Nerve
Nervi nervorum
 Nerve of Nerve

47. Classification of peripheral nerves
Cranial nerves :
Spinal nerves:
Splanchnic nerve
Sensory nerves
Motor nerves
Mixed nerves

48. Cranial nerves
12 cranial nerves
 2 attach to forebrain (Tel- &
Diencephalon)
 10 attach to brainstem
(Mes-, Met- and Myelencephalon)
“0” pair cranial nerve
“nervi terminalis”
Motor :3,4,6,11,12
Sensory : 1,2,8
Mixed : 5,7,9,10

49. 1. Olfactory
2. Optic
3. Occulomotor
4. Trochlear
5. Trigeminal
6. Abducent
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10.Vagus
11.Accesary
12.Hypoglossal
Oh, Once One
Takes The
Anatomy Final,
Very Good
Vacations
Appear
Heavenly

50. Olfactory Nerve (= CN or N I)
C: Sensory
O: Olfactory Epithelium in nasal cavity
D: Olfactory bulbs (by way of cribriform plate of
ethmoid)
Only CN directly attached to Cerebrum

51. Optic Nerve (N II)
C: Sensory
O: Retina
D: by way of optic
foramen of
sphenoid to
Diencephalon
(optic chiasma)
and to occipital
lobe

52. Oculomotor (N III)
C: Motor
O: Mesencephalon
D: Somatic motor to
superior, inferior,
medial recti and
inferior oblique;
visceral motor to
intrinsic eye muscles
by way of superior
orbital fissure
SO4, LR6, Rest are by 3

53. Trochlear (N IV)
C: Motor
O: Mesencephalon
D: superior oblique muscle
by way of superior
orbital fissure

54. Trigeminal (CN V)
C: Mixed
three major branches
1. Ophthalmic (sensory)
2. Maxillary (sensory)
3. Mandibular (mixed)
O: face / nuclei of pons
D: sensory nuclei in pons /
muscles of mastication

55. Abducens
(CN VI)
C: Motor
O: Pons
D: Lateral rectus eye muscle

56. Facial (CN VII)
C: Mixed
O: sensory from taste receptors
of anterior 2/3 of tongue /
motor from pons
D: Sensory to sensory nuclei of
pons / motor muscles of facial
expression, visceral motor to
tear gland.
Bell’s Palsy

57. Vestibulocochlear (CN VIII)
C: Sensory
O: Receptors of
inner Ear
D: Nuclei in Pons
and medulla
oblongata
acoustic nerve

58. Glossopharyngeal (CN IX)
C: mixed
O: sensory from posterior
1/3 of tongue / motor from
medulla oblongata
D: medulla / muscles for
swallowing, parotid gland
Stylopharyngeus

59. Vagus (CN X)
C: Mixed
O: Sensation from pharyngeal area and outer
ear / motor from medulla
D: Sensory to medulla / visceral (autonomic)
motor to thoracic and abdominal cavities
and their organs. Major motor pathway for
ANS
Most important Cranial Nerve!

61. Accessory (CN XI) Spinal Accessory
C: Motor
O: Motor nuclei of medulla and
spinal cord
D: Swallowing, trapezius &
sternocleidomastoid muscles
Hypoglossal (N XII)
C: Motor
O: Motor nuclei of medulla
D: Tongue musculature

63. Spinal nerves
31 pairs of spinal nerves
 8 cervical
 12 thoracic
 5 lumber
 5 sacral
 1 coccygeal

64. Organization of Spinal Nerves:
1. Root – inside vertebral canal
a. dorsal sensory root with a ganglion
b. ventral motor root
2. Mixed spinal nerve
3. Rami
a. dorsal - mixed to skin and muscles of back
b. ventral - mixed “spinal nerve” to ventrolateral body surfaces
and limbs
c. white ramus communicans motor ANS
d. gray ramus communicans motor ANS

67. Dermatomes
Sensory
innervations by
specific spinal
nerves  Each pair of
spinal nerves monitors
specific region of body
surface.

68. Principal Plexuses
A blend, or network, of nerve
fibers from several spinal
roots.
• Cervical plexus
• Brachial plexus
• Lumbar plexus
• Sacral plexus

69. Cervical Plexus
Phrenic nerve
- innervates
diaphragm

70. Brachial Plexus

71. Nerves
of the Arm
Musculocutaneous nerve
– innervates biceps and
brachialis muscles
Median nerve - innervates
lateral flexors
Ulnar nerve - innervates
medial flexors
Radial nerve - innervates
forearm extensors

72. Lumbar
Plexus
Femoral Nerve
Lumbosacral Trunk
(to Sciatic Nerve)
Obturator Nerve

73. Sacral Plexus

74. Nerves of the Lower limb
• Sciatic N.
•Thickest and Longest
•Branches to Tibial and
Fibular Nerves
• Femoral N.
•Front of Thigh
• Obturator Nerve
•Medial side of thigh

75. Synapse
Site of communication
between two nerve cells or
nerve cell and effector cell
 Presynaptic and
postsynaptic neurons
neuro-effector junctions,
e.g., Motor End Plate
Electrical vs.
chemical synapses

76. Types of synapses
Axodendritic
(commonest)
Axosomatic
Axoaxonic
Dendrosomatic
Dendrodendritic
Dendroaxonic

77. Chemical Synapse vs. Electrical Synapse
Space between two cells
Signal transduction via a
neurotransmitter, usually
ACh
Most common
Direct physical contact between cells =
gap junctions
Direct signal transduction
Rare, but occurs in CNS and HEART

78. Chem.
Synapse
Structure
1. Axon terminal of presynaptic cell, with vesicles of
neurotransmitter(NT)
2. Synaptic cleft
3. Dendrite or cell body of postsynaptic cell
4. Unidirectional

80. Conduction of action potential
The “signal,” or Action
Potential is carried along
the Neurilemma Sheath
Faster if axon is
myelinated

81. Autonomic
Nervous
system

83. Overview of ANS
Pathway for Visceral Motor Output
The somatic NS uses one effector nerve but the
ANS output always involves two neurons
between spinal cord (CNS) and effector.

84. Overview of ANS
ANS has two divisions with both structural
AND functional differences:
1. Parasympathetic – Rest and Repose
1. Craniosacral output
2. Digestion, “housekeeping”
3. Postganglionic axons release Ach
(Cholinergic)
2. Sympathetic- Fight or Flight
1. Thoracolumbar output
2. Heart Rate, Respiration
3. Vasoconstriction
4. Postganglionic axons release NE
(Adrenergic)

85. •Craniosacral division
Preganglionic neurons (cell bodies)
located in brain stem & sacral segments
of spinal cord.
Cranial Nerves III, VII, IX, X
Pupils (III), Lacrimal and Salivary Glands
(VII), Viscera (X)
Sacral segments S2-4
Bladder, Genitals
1. Parasympathetic
Division

86. Parasympathetic =
Craniosacral

87. Constriction of Pupils (opposite
sympathetic)
Secretion of Digestive Glands
Secretion of Digestive Hormones
 Insulin, etc.
Visceral Smooth Muscles
Defecation and Urination
Constriction of Respiratory System
Decrease Heart Rate
Sexual Arousal
Parasympathetic
Division
Some functions:

88. 2. Sympathetic
Division
Thoracolumbar division
Preganglionic neurons (cell bodies) located
between T1 & L2 of spinal cord
Ganglionic neurons (cell bodies) in ganglia
near vertebral column, AKA “Chain
Ganglia.”
Paravertebral ganglia = sympathetic chain
ganglia
Prevertebral ganglia = collateral ganglia
Special case: adrenal medulla is a modified
ganglion

90. Sympathetic Efferent Pathways:
Examples

92. Special Case:
Adrenal Medulla
Fig. 17-6
“Modified sympathetic ganglion”
Terminus for neuron #1, stimulates
specialized 2nd order neurons with
very short axons in adrenal medulla
to release NT into blood stream (=
hormones)
Epinephrine (adrenaline) ~ 80% and
norepinephrine (noradrenaline)
Endocrine effects are longer lasting
than nervous system effects

93. Dual Innervation
Each organ receives
innervation from
sympathetic and
parasympathetic fibers
Fibers of both divisions meet
& commingle at plexuses
(fig 17-9) to innervate
organs close to those
centers
Names of plexuses derived
from locations or organs
involved

94. Comparison

95. Sympathetic
Thoraco-lumbar [ T1 – L2]
Preganglionic fibre – Short
Postganglionic Fibre - Long
Nerve ending - Adrenergic
Fight or Flight
Works for Today
Sphincter - Closed
Nerve of emergency
Parasympathetic
Cranio-sacral
[III, VII, IX, X, S2,S3, S4]
Long
Short
Cholinergic
Rest & Digest
Works for tomorrow
Relax
Nerve of tranquility

96. ANS
Summary

97. Referred pain

98. Horner’s Syndrome
Loss of sympathetic
innervation to an eye
Ptosis
Miosis
Anhidrosis
Enophthalmos
Loss of Cilio-spinal reflex

101. All The Best