The document provides an overview of the nervous system. Some key points: - The nervous system regulates body activities through rapid nerve impulses and is one of the most complex systems despite its small mass of 2 kg. - The branch of medicine concerned with studying and treating the nervous system is neurology, and physicians who diagnose and treat nervous system disorders are neurologists. - The nervous system consists of the central nervous system (brain and spinal cord) and peripheral nervous system. It receives sensory input and provides motor output through somatic and autonomic functions.

1. The Nervous
System
Prepared by
Livson Thomas
M.Sc. (N)
CON-CHB
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2. The Nervous System
• The NS regulates body activities by responding rapidly using nerve
impulses.
• The mass of the nervous system is approximately 2 kgs, one of the
smallest system yet the most complex
• The branch od medicine that is concerned with study and treatment
of the nervous system is called Neurology.
• A physician who diagnose and treat disorders of nervous system is a
Neurologist.
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3. LT

4. Central Nervous System (CNS)
Somatic Senses Special Senses
Somatic Nervous
System
Skeletal Muscles
Autonomic
Nervous System
Sympathetic
Nervous
System
Parasympath
etic Nervous
system
Enteric
Nervous
System
Smooth muscles, cardiac muscle
and glands
Smooth
muscles
and glands
of GI tract
Sensory Input Motor Output
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5. Functions of the Nervous System
1. Co-ordinate
2. Controls
3. Maintain Homeostasis
Sensory function: Detect internal & external stimuli
Integrative Function : Processing of sensory information by analysing and
making decisions
Motor Functions: Effect on muscles and glands
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6. Nervous Tissue
Two types
- Neurons
- Neuroglia
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7. Neurons
• Neurons are the nerve cells
• Poses electrical excitability:
responds to a stimulus and
converts it into action
potential (nerve impulse).
• Nerve impulses occurs due
to the movement of ions
between interstitial fluid
and inside of neurons
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8. LT

9. Overview of Neurons
Main three Parts
- A cell body
- Dendrites
- An Axon
- Diameter: 5 μm to 135 μm
- Bundles of axon forms the nerves
- Neurons cannot divide
- For survival they need continuous supply of oxygen and glucose
- Neurons can synthesis chemical energy (ATP) only from glucose
- Neurons generate and transmit electrical impulses called action potential
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10. • Cell body
Also known as Soma
Contains a nucleus surrounded by cytoplasm including all the typical cellular
organelles.
• Dendrites
Receiving or input portion of a neuron
They contain numerous receptor sites for binding chemical messengers
Usually short and highly branched (Tree shaped)
• Axon
This part propagates nerve impulses to other neurons or muscles or a gland cell.
Contains axoplasm and axolemma
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11. • Axon hillock
The place at which cell body and axon joins
• Schwann cell
Insulates the axon
Contains cytoplasm, myelin sheath and neurolemma
• Axon terminal
Place where the impulse is transmitted to the next neuron, muscle or gland
Synaptic end bulb is present here where synapses takes place.
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12. Classification of Neurons
Based on structure:
1. Multipolar : Several dendrites and one axon
2. Bipolar: One dendrite and one axon
3. Unipolar: Dendrites and axons are fused
Based on histology:
1. Purkinje cells
2. Pyramidal cells
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13. Based on function:
1. Sensory or afferent neuron
2. Motor or efferent neurons
3. Interneurons or association neurons
Based on myelination
1. Myelinated neuron
2. Unmyelinated neuron
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14. Neuroglia
• About half the volume of CNS
• Glue that holds the nervous tissue.
• Actively participate in the activities
of the nervous tissue
• They do not generate or propagate
action potential
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15. Types of neuroglia
1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal cell
5. Schwann cells
6. Satellite cells
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16. Myelination
• Some neurons are covered by a multi-layered lipid and protein called myelin
sheath
• These neurons are called as myelinated neurons.
• The sheath electrically insulates the axon and increases the speed of nerve
impulse conduction
• Myelin sheath produced by : Schwann cells in PNS
Oligodendrocytes in CNS
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18. Collection of Nervous Tissue
• Neuronal cell bodies are often grouped
together in clusters – GANGLION (PNS),
NUCLEUS (CNS)
• The axons of neurons are usually grouped
together in bundles – NERVE (PNS) ,
TRACT (CNS)
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19. Gray Matter and White Matter
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20. •Gray Matter:
It contains Neuronal cell bodies, dendrites, unmyelinated
axons, axon terminals and neuroglia.
The Nissl bodies gives the gray colour.
•White Matter:
It is composed primarily of the myelinated axons
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21. Electrical Signals in Neurons
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22. Electric Signals
• Two types of electric signals
1. Graded Potential
2. Action Potential
Graded potential triggers an action potential
Ion channels in Neurons
• Leak Channels
• Ligand- gated channels
• Mechanically- gated channels
• Voltage gated channels
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23. Resting Membrane
Potential
• Build up of negative ions in
the cytosol along side the
inside of the membrane
• Equal build up of positive
ions in the ECF along side
the outer surface of the
membrane.
• Resting membrane
potential is typically – 70
mV
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24. Graded Potential
• Small deviation from RMP.
• Makes membrane more polarized or less polarized
• More polarized : Hyperpolarizing GP
• Less Polarizing : Depolarizing GP
• Occurs due to stimulus by Mechanically gated or Ligand gated
channels
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25. Action Potential
• It is also known as impulse
• Sequence of rapidly occurring events that decrease and reverse the
membrane potential and eventually restore it to the resting state.
• Phases
1. Depolarizing phase
2. Repolarizing phase
3. Hyperpolarization
4. RMP
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26. • Two types of voltage gated channels open and then close
1. Voltage gated Na+ channels
2. Voltage gated K+ channels
• Na channel opens first : Na+ rushes inside – Depolarizing phase
• K+ channel opens: K+ rushes out of cell – Repolarizing phase
• Action potential in the membrane of the axon occurs when depolarization
reaches threshold (- 55mV)
• Resting state  Depolarizing phase  Repolarization  RMP
• Conduction of action potential is called Propagation
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27. Factors affecting speed of propagation
1. Amount of myelination
2. Axon diameter
3. Temperature
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28. Action Potential
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29. Classification of Nerve Fibers
A Nerve fibers
• Largest diameter axons (5 – 20 μm)
• Myelinated
• Propagation speed: 12 to 130 m/sec (44 – 460 kms / hr)
• Eg: Sensory neurons for touch, pressure, position of joints, thermal
and pain sensation, motor neurons of skeletal muscles.
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30. B Nerve Fibers
• Diameter 2 – 3 μm
• Myelinated
• Propagation speed : 15 m/sec (55 kms/hr)
• Conduct sensory nerve impulse from the viscera to the brain and spinal cord
• All the axons of the Autonomic Motor Neurons
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31. C Nerve Fibers
• Smallest diameter axons ( 0.5 – 1.5 μm)
• Unmyelinated
• Speed of Propagation : 0.5 to 2 m/sec (1 – 6 kms/ hr)
• Supports the B Nerve fibers
• Conduct some sensory impulses for pain, ouch, pressure, heat and cold from
the skin.
• Helps in constricting and dilating the pupils, increasing and decreasing heart
rate, and contracting and relaxing the Urinary bladder
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32. Why is Graded Potential Needed ?
• Graded potentials are small changes in membrane potential that
are either excitatory (depolarize the membrane) or inhibitory
(hyperpolarize the membrane). Many excitatory graded potentials
must happen at once to depolarize the cell body enough to trigger
the action potential.
• The importance of these graded interactions is that they greatly
increase the functional capacity of the nervous system.
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33. Signal
Transmission
• Synapse is the region
where communication
occurs between a neuron
and an effector cell or
another neuron.
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34. Synapse
Pre- Synaptic Neuron
Post- Synaptic Neuron
Two types of Synapse
1. Electrical
2. Chemical
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35. Electrical
Synapse
Action potential
(impulse) conduct
directly between the
plasma membranes of
adjacent neuron
through structures
called gap junctions
Present in brain, smooth
muscles, cardiac
muscles and developing
embryo
Advantages:
• Faster Communication
• Synchronization
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36. Chemical Synapse
• Pre and post synaptic neuron are close, but do not touch
• Separated by synaptic cleft (interstitial fluid) – 20 to 50 nm
• Process
1. A nerve impulse arrives at synaptic end bulb
2. Depolarization opens voltage gated Ca2+ channels (inflow of Ca2+ from ECF)
3. Synaptic vesicles adhere to plasma membrane and exocytosis takes place and
releases content to synaptic cleft
4. Neurotransmitter binds to post synaptic receptors and open ligand gated ion
channels.
5. Inflow of ions causes change in membrane voltage – Depolarization
6. When Post synaptic neuron reaches threshold – action potential is triggered.
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37. Neurotransmitters
• Neurotransmitters are endogenous chemicals that allow neurons to communicate
with each other throughout the body.
• Approx 100 of neurotransmitters are present.
• Example of some neurotransmitters:
Acetylcholine
Dopamine
Histamine
Gamma aminobutyric Acid (GABA)
Serotonin
Norepinephrine
Glutamate
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38. Central Nervous System
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39. Major parts
of the brain
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40. Protective Covering of the Brain
•The cranium and the
cranial meninges surround
and protect the brain
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41. Protective
layers
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42. LT

43. Meninges
• The cranial meninges are continuous with the spinal meninges and have the
same basic structure.
a. Dura Mater b. Arachnoid Mater c. Pia Mater
• But: Cranial dura mater has two layer, the spinal dura mater has only one.
• Two layers of cranial dura mater: 1. Periosteal layer
2. Meningeal layer
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44. Separation of brain
• 3 extensions of Dura mater
separate parts of the brain
1. Falx cerebri : Separates two
hemispheres of the
cerebrum
2. Falx Cerebelli: Separates
two hemispheres of
cerebellum
3. Tentorium cerebelli:
Separates cerebrum from
cerebellum
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45. Blood supply to the Brain
• Common carotid Arteries – Right and Left
• Internal Carotid Arteries
• External Carotid Arteries
• Basilar artery
• Cerebral arterial Circle (Circle of Willis)
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46. Blood flow to the brain
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47. Blood flow of the brain
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48. Blood- Brain Barrier
• A network of blood vessels and
tissue that is made up of closely
spaced cells and helps keep
harmful substances from reaching
the brain.
• The blood-brain barrier lets some
substances, such as water, oxygen,
carbon dioxide, and general
anesthetics, pass into the brain.
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49. Difference between a normal blood vessel and BBB blood
vessel
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50. • Parts of the brain that do not have the BBB
• The seven circumventricular organs
are the
- Area postrema (AP),
- Median eminence (ME),
- Neurohypophysis (N),
- Organum vasculosum of the lamina
terminalis (OVLT),
- Pineal (P),
- Subcommissural organ (SCO)
- Subfornical organ (SFO)
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51. Cerebrospinal Fluid
(CSF)
• It’s a clear colorless liquid composed
primarily of water that protects the brain
and spinal cord from chemical and physical
injuries
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52. Ventricles of
the brain
Four ventricles are
present in the brain
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53. CSF PRODUCTION PATHWAY
Through foramen of Monro
3rd Ventricles
Through Aqueduct of sylvius
4th Ventricles
Sub Arachnoid Space
Reabsorbed by
Arachnoid Villi of
dural venous sinuses
CSF is produced by the
Choroid Plexus of lateral, 3rd & 4th
ventricles
Through foramen of Luschka & Megendie
Circulates around the brain
Lateral Ventricles
Heart & Lungs
Arterial
Blood
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54. Composition of CSF
• Total Volume: 80 to 150 mL
CSF contains small amounts of :
• Glucose,
• Proteins
• Lactic acid
• Urea
• Cations (Na+, K+, Ca2+, Mg2+)
• Anions (Cl- & HCO3
-)
• Some WBCs
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55. Function of CSF
1. Mechanical Protection
2. Chemical Protection
3. Circulation
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56. Lumbar Puncture
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57. Brain Stem
• Part between the spinal cord and the diencephalon
• Three structures are present:
1) Midbrain
2) Pons
3) Medulla Oblongata
Extending through the brain stem is the Reticular formation.
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58. Medulla Oblongata
• Forms the inferior of the brain stem.
• Medullas white matter contains all sensory (ascending) tracts and motor
(descending) tracts.
• Some white matter forms bulges on the anterior aspect called pyramids
• Pyramids are formed by large
corticospinal tracts.
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59. Medulla cont…
• The corticospinal tracts control the voluntary movement of the limbs and trunk.
• At junction of medulla to spinal cord 90% of axon in the right pyramid crosses
to the left side and vice versa.
• This crossing is called decussation of pyramids
• The medulla also contains several neuronal cell bodies.
• Controls vital activities
- Cardiovascular center
- Medullary respiratory center
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60. Functions of Medulla Oblongata
Rate and force of heartbeat
Rhythm of breathing
Diameter of blood vessels
Vomiting
Swallowing - deglutition
Sneezing
Coughing
Hicupping
Sensory pathway for taste, hearing and balance
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61. Pons (= bridge)
• Lies superior to the medulla and anterior to the cerebellum
• Size: 2.5 cm
• Pons also consist of nuclei and tracts.
• The pons is a bridge that connects parts of brain with one another
• Two structural component
- Ventral
- Dorsal
• Coordinating and maximizing the efficiency of
voluntary motor out put throughout the body
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62. Midbrain
• Also known as mesencephalon
• Extends from pons to the diencephalon
• Size: 2.5 cm
• Contains both nuclei and tracts
• The anterior part of midbrain contains paired bundles of axons known as
cerebral peduncles
- conduct nerve impulses from motor areas in cerebral cortex to sc,
medulla and pons.
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63. Midbrain cont..
• The posterior part is called tectum
- Reflex centers for visual activity
- Eye movement for tracking moving objects
- Scanning stationary images
- Movement of head, eyes and trunk in response to visual stimuli.
- Startle reflex
- Subconscious muscle activity
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64. Reticular Formation
• Clusters of small clusters of
neuronal cell bodies (Gray matter)
interspersed among small bundles
of myelinated axons (White matter).
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65. Reticular formation cont..
• Location: extends from superior part of the
spinal cord throughout the brain stem into
the inferior part of the diencephalon.
• Ascending portion is called the Reticular
Activating System (RAS)
• Function
- Consciousness: a state of wakefulness
in which an individual is fully alert, aware and
oriented.
- Concentration/ attention
- Awakening from sleep
- Filters out insignificant information
Damage to RAS leads to
COMA
Descending part of the RF helps
in maintaining muscle tone,
heart rate, BP and Resp. rate
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66. • Inactivation of RAS produces sleep, a state
of partial consciousness from which the
person can be awakened.
• Damage to RAS leads to COMA
• Descending portion of RAS connects to
cerebellum and SC
- Helps regulate muscle tone
- Assist in regulation of HR, BP and RR
RAS receives sensory input from the
EYES, EARS and other sensory
receptors except Sense of SMELL
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67. The Cerebellum
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68. Anatomy of cerebellum
• Occupies the inferior and posterior aspect of the
cranial cavity
• Surface is folded like the cerebrum and contain gray
matter on the outside.
• 1/10 of the brain mass.
• The transverse fissure and tentorium cerebelli
separates cerebrum from cerebellum.
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69. Anatomy of cerebellum cont….
• Shape: resembles a butterfly
• Central area: vermis
• Lateral wings or lobes : cerebellar
hemispheres.
• Anterior and posterior lobe controls
subconscious aspect of skeletal
muscle movements
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70. Anatomy of the Cerebellum
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71. • Primary function:
Evaluation of movements initiated by motor areas in cerebrum
If movement is not correct
Sends feedback to motor area in cerebrum to correct the errors in action
• Other functions
- Equilibrium & balance
- Proprioception
- Coordinates skilled movements (catching a ball, dancing etc.)
Anatomy of cerebellum cont….
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72. Proprioception
• Proprioception (or
kinesthesia) is the sense
through which we
perceive the position
and movement of our
body, including our
sense of equilibrium and
balance, senses that
depend on the notion of
force
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73. LT

74. Function of
cerebellum
•Evaluation of movements initiated
by the motor areas.
•Coordinates skilled movements
•Regulates posture and balance
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75. The Diencephalon
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76. Thalamus
• Measures: 3 cm
• 80% of the diencephalon
• Function
- Relays almost all sensory input to
cerebral cortex.
- Helps in maintenance of consciousness.
- Helps in transmitting information from
cerebellum to primary motor area of
cerebral cortex
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77. Hypothalamus : Small part of the diencephalon
Functions:
- Controls and integrates activities of
ANS.
- Produces hormones (releasing
hormones, inhibiting hormones,
oxytocin, ADH)
- Regulates emotional and behavioral
patterns.
- Feeding and satiety centers
- Thirst centers
- Controls the body temperature-
Thermoregulation
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78. Epithalamus
• Consist of the
Pineal gland
Habenular nuclei
• Functions
Pineal gland- secretes melatonin
(Circadian Rhythm, antioxidant, induces sleep)
Habenular nuclei- helps in olfaction
(emotional responses to odor)
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79. Circumventricular Organs
• This is part of the diencephalon
• Lie in the wall of the third ventricle.
• They can monitor chemical changes in the
blood (No BBB)
• CVOs includes part of
- hypothalamus, pineal gland, pituitary
gland, some other parts
Function: Coordination of homeostatic activities
of NS and Endo. System
CVOs acts as a site for entry of HIV, and other
viruses and bacteria to the brain
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80. The Cerebrum
The place of intelligence
• Ability to read, write and speak,
• To make calculation
• To compose music
• Remember the past
• Plan for the future
• Imagine things
Cerebrum consist of :
- Outer cerebral cortex
- Internal region of cerebral white matter
- Basal nuclei
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81. Cerebral Cortex
• Region of gray matter that forms the outer rim of
the cerebrum
• 2 to 4 mm thick
• Contains billions of neurons
• The folds are called gyri or convolutions
• Shallow grooves is called sulci
• Deep grooves are called fissures
• Longitudinal fissure divides the hemispheres
• Cerebral hemispheres are connected internally
by the corpus callosum
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82. Lobes of the cerebrum
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83. Major sulcus of the cerebrum
• The central sulcus separates the frontal lob
from the parietal lobe.
• The lateral cerebral sulcus separates frontal
lobe from the temporal lobe.
• The parieto-occipital sulcus separates the
parietal lobe from the occipital lobe.
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84. LT

85. Functions of the lobes
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86. Cerebral Hemisphere
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87. Functional differences between right and left hemisphere
Right Hemisphere Left Hemisphere
• Receives somatic sensory signals
from and controls muscles on
left side of body
• Musical and artistic awareness
• Space and pattern perception
• Recognition of faces and
emotional content of facial
expressions.
• Generating emotional content
of language
• Generating mental images to
compare spatial relationship
• Identifying and discriminating
among odors
• Receives somatic sensory signals
from, and controls muscles on
right side of body
• Reasoning
• Numeric and scientific skills
• Ability to use and understand
sign language
• Spoken and written language
• Group coordination and
communication
• Verbal memory
• Critical thinking
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88. Brain
Waves
• Neurons are generating millions of nerve
impulses (action potentials).
• Together, these electrical signals are called
brain waves
• Our brainwaves change according to what
we’re doing and feeling.
• The brain waves generated close to the brain
surface can be detected by sensors called
electrodes placed on forehead and scalps
• The recording of brain waves is called
Electroencephalogram (EEG)
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89. EEG
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90. 5 types of
brain waves
1. Alpha waves α
2. Beta waves β
3. Theta waves θ
4. Delta waves δ
5. Gamma waves γ
Brainwave speed is measured in Hertz (cycles
per second) and they are divided into bands
delineating slow, moderate, and fast waves.
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91. Alpha Waves
• Frequency 8 to 12 Hertz
• Dominant during
- Quietly flowing thoughts
- Meditation
• Resting state for the brain.
• Alpha waves help in mental coordination, calmness, alertness,
mind/body integration and learning.
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92. Beta Waves
• Frequency : 12 to 38 Hz
• Dominant during
- Sate of consciousness
- Cognitive tasks
• Present wen we are attentive, alert, engaged in problem solving,
decision making and focused
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93. Theta Waves
• Frequency: 3 to 8 Hz
• Dominant
- During sleep
- Deep meditation
• Our gateway to learning, memory, intuition.
• During theta waves our senses are withdrawn from external world and focused
on signals from within
• Dream, imagination, intuitions, nightmares, our fears
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94. Delta waves
• Frequency: 0.5 to 3 Hz
• Slow and low frequency waves
• Deepest meditation and dreamless sleep
• Healing and regeneration are stimulated in this state
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95. Gamma waves
•Frequency : 38 to 42 Hz
•Fastest brain waves with high frequency
•Gamma brain waves pass information rapidly
•Achievement of peak concentration
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96. LT

97. Cranial Nerves
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98. Nerve
No.
Cranial Nerves Components Principal Functions
I Olfactory Sensory • Smell- olfaction
II Optic Sensory • Vision- sight
III Oculomotor Motor • Movement of eyeball
• Accommodation of lens
• Constriction of pupil
IV Trochlear Motor • Movement of eyeballs
V Trigeminal Mixed or Both • Touch, pain, thermal sensation from scalp,
face and oral cavity
• Chewing
• Controls middle ear muscles
VI Abducens Motor • Movement of eyeballs
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99. Nerve
No.
Cranial Nerve Components Principal Function
VII Facial Mixed or Both • Taste from anterior two-thirds of
tongue.
• Touch, pain, thermal sensation
from skin in external ear canal
• Control of muscles for facial
expression
• Secretion of tears and saliva
VIII Vestibulochoclear Sensory • Hearing and Equilibrium
IX Glossopharyngeal Mixed • Taste from posterior one third of
tongue
• Proprioception
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100. Nerve
No
Cranial Nerves Component Principal Function
X Vagus Mixed • Taste from epiglottis
• Proprioception from throat and voice box
• Monitors blood pressure, oxygen & CO2
levels in blood
• Touch, pain and thermal sensation from
skin of external ear
• Sensation from thoracic and abdominal
organs
• Swallowing, vocalization, coughing
• Motility and secretion of GI organs
• Constriction of respiratory pathways
• Decrease heart rate
XI Accessory Motor • Movement of head and pectoral girdle
XII Hypoglossal Motor • Speech, manipulation of food and
swallowing
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101. The Spinal Cord
• More than 10 crore neurons and even
more neuroglia composes the spinal
cord.
• It is the part of the CNS that extends
from the brain.
• Spinal cord reflex: A quick, automatic
response to certain kinds of stimuli that
involves only the neurons in spinal cord
and spinal nerves.
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102. Anatomy
• SC is the elongated, almost cylindrical
part of the CNS, which is suspended in the
vertebral canal surrounded by meninges
and CSF
• A specimen of CSF can be taken using a
procedure called lumbar puncture
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103. External Anatomy
• Roughly oval.
• Medulla Oblongata Second Lumbar Vertebrae
• Two enlargements present
- Cervical Enlargement [C4 to T1] : nerves to and from upper limbs
- Lumbar Enlargement [T9 to T12]: nerves to and from lower limbs
• Spinal cord terminates as a tapering , conical structure called conus medullaris [L1-L2]
• The cauda equina is the continuation of these nerve roots in the lumbar and sacral
region. These nerves send and receive messages to and from the lower limbs and
pelvic organs.
• Filum terminale anchors the spinal cord to the coccyx
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104. LT

105. Internal Anatomy
• A transverse section shows white matter that surrounds an inner core
of grey matter.
• Two grooves divide the white matter of spinal cord and divide into
right and left
- Anterior Median Fissure (Ventral Side)
- Posterior Median Sulcus (Dorsal side)
• Grey matter is shaped like H or a butterfly: consist of dendrites and
cell bodies of neurons, unmyelinated axons and neuroglia.
• Gray commissure forms the center of the H and consist of the central
canal filled with CSF
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106. Internal anatomy
• Gray matter is subdivided into regions
called horns
- Posterior Gray Horns (incoming
sensory neurons)
- Anterior Gray Horns (somatic
motor neurons- provides impulse
for contraction of skeletal muscles)
- Lateral Gray Horn (T –L):
Autonomic motor neurons –
regulates activity of cardiac muscle,
smooth muscles and glands
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107. LT

108. Cross section of Spinal Cord
Grey mater in the center surrounded by white mater
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109. Protective structures of SC
1. Vertebral column: Spinal cord
passes through the vertebral
foramina of all vertebrae,
stacked on top of the other to
form the vertebral canal
2. Meninges: Protect with the
three connective tissues –
dura mater –arachnoid mater
– pia mater
3. Fat & CT
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110. Spinal Nerves
• All the nerves associated with the
spinal cord are called spinal nerves
• Spinal nerves connect the CNS to
sensory receptors, muscles and glands
in all parts of the body
• There are total 31 pairs of spinal
nerves (named according to the region
and level of the vertebral column)
• Endoneurium – Perineurium - Epineurium
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111. Distribution of Spinal Nerves
• The spinal nerves divide into several
branches after passing through the
intervertebral foramen.
• These branches are called as Rami
• The posterior ramus (dorsal) serves the deep
muscles and skin of the posterior surface of
the trunk.
• The anterior ramus (ventral) serves the
muscles and structures of the upper and
lower limb and the skin of the lateral and
anterior surface of the trunk.
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112. • Spinal nerve also has a
meningeal branch.
• This branch re-enters the
vertebral cavity through the
intervertebral foramen and
supplies the vertebrae,
vertebral ligament, blood
vessels of spinal cord and
meninges.
• Rami communicantes: the
spinal nerve branch which is
component of the
autonomic nervous system.
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113. LT

114. Plexuses
• Axons from anterior rami of spinal
nerves, except for thoracic nerves T2 –
T12 , do not go directly to the body
structures they supply.
• They form networks on both left and
right
• Principal Plexuses are:
- Cervical
- Brachial
- Lumbar
- Sacral
- Coccygeal
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115. Intercostal nerves
• The anterior rami of spinal
nerves from T2 to T12 do not
form plexuses and are known as
intercostal nerves
• They supply structures in the
intercostal space
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116. Layers of the Nerve Tissue
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117. Dermatomes
• The skin of the entire body is supplied by somatic
sensory neurons that carry nerve impulses from the
skin into the spinal cord and brain.
• Each Spinal nerve has specific segment of the body.
• Face & scalp: Trigeminal nerve
• The area of the skin that provides sensory input to the
CNS via spinal nerves is called Dermatomes
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118. Cervical Plexus
•Formation : C1-C5 with some C5
•Function:
- Supplies skin and muscles of the
head, neck, superior part of shoulders
and chest.
- Phrenic nerve from CP supply
the diaphragm.
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119. Brachial Plexus
• Formation: C5-C8 & T1
• Functions:
- Entire nerve supply to
shoulders and upper limbs
- Muscles of arm
- Muscles of forearm
- Muscles of hand
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120. Lumbar Plexus
• Formation : L1 to L4
• Function:
- Supply the antero-lateral
abdominal wall
- External genitals
- parts of lower limb
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121. Sacral Plexus
• Formation: L4 - L5 & S1 – S4
• Situated anterior to the sacrum
• Function:
- Supplies the buttocks
- Perineum, pelvis
- Lower limbs
• The largest nerve in the body the Sciatic Nerve arises from sacral plexus
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122. Coccygeal Plexus
• Formation: S4-S5 &
Coccygeal nerve
• Sensory and motor
innervation to their
respective dermatomes
and myotomes.
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123. Reflexes
• A reflex is a fast, involuntary, unplanned sequence of actions that occur in
response to a particular stimuli.
Types
Biceps reflex (C5, C6)
Brachioradialis reflex (C5, C6, C7)
Extensor digitorum reflex (C6, C7)
Triceps reflex (C6, C7, C8)
Patellar reflex or knee-jerk reflex (L2, L3, L4)
Ankle jerk reflex (Achilles reflex) (S1, S2)
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124. Sensation
• Conscious or subconscious awareness of
changes in the external or internal
environment
• Sensory impulse reaching lower brain stem:
- Complex reflexes: Heart rate, breathing
rate
• Sensory impulse reaching cerebral cortex:
- Touch, pain, hearing, taste
Perception: conscious interpretation of
sensations and is a primary function of the
cerebral cortex.
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125. Classification of sensations
a. Somatic senses
- Touch
- Pressure
- Vibration
- Itch
- Tickle
- Warm & Cold
- Pain
- Proprioception
b. Visceral Senses (Conditions within
internal organs)
- Pressure
- Stretch
- Chemicals
- Nausea
- Hunger
- Temperature
I. General Senses
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126. II.
Special
Senses
Smell Taste Vision/ Sight
Hearing Equilibrium/
Balance
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127. The process of sensation
Stimulation of the Sensory Receptors
Transduction of stimulus
Generation of Nerve Impulse
Integration of Sensory Input
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128. Process of Sensation
Stimulation Transduction Generation Integration
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129. Sensory Receptors
Grouped on bases of:
1. Microscopic Structures
2. Location of the receptors and
origin of stimuli that activates them
3. Type of stimulus detected
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130. Microscopic Structure
• Free nerve endings:
- Seen under light microscope.
- Receptors for pain, temperature, tickle, itch.
• Encapsulated nerve endings
- Receptors for pressure, vibration and touch
• Separate cells that synapse with first order
sensory neurons
- hair cells for hearing and equilibrium
- Gustatory receptors in taste buds
- Photoreceptors in eye
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131. Location of Receptors and
Origin of Activating Stimuli
• Exteroceptors
- Located at or near the
external surface of the
body
- Sensitive to stimuli
outside the body
- Provide information about
external environment
- Hearing, vision, smell,
taste, touch, pressure,
vibration, temperature &
pain
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132. • Interoceptors
- Located in blood vessels, visceral organs, muscles, nervous
system
- Monitor the internal environment
• Proprioceptors
- Located in muscles, tendons, joints & inner ear.
- Provide information about body position, movement of body,
joints
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133. Type of Stimulus detected
• Mechanoreceptors
- sensitive to mechanical stimuli
- deformation, stretching, bending of cells
- provide sensation of touch, pressure, vibration, proprioception,
hearing & equilibrium
- Stretching of blood vessel & internal organs
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134. Thermoreceptors :
Detect change in
temperature
Nociceptors:
Respond to painful
stimuli due to
chemical or physical
damage to tissue.
Photoreceptors:
Detects light that
strike the retina of the
eye.
Chemoreceptors: Detect
chemicals in mouth
(taste), smell and body
fluids
Osmoreceptors: Sense
osmotic pressure of
body fluids.
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135. Pain Sensation
• Pain is needed for survival
• It serves as a protective function
by signaling the presence of
dangerous, tissue damaging
conditions
• Pain is the uncomfortable
sensation in the body
• In Medicine: Identifying the
location of pain helps in finding
the underlying cause of a disease.
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136. Pain Pathway
Nociceptors
Intense mechanical or chemical
stimuli activates nociceptors
Release of chemicals such as
prostaglandins, potassium ions
Pain is experienced. Pain persist
even after the stimuli is removed
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137. Distribution of referred pain
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138. Common
Disorders of
the Nervous
system
• Increased Intracranial
Pressure
• Cerebral Oedema
• Hydrocephalus
• Head Injuries
• Intracranial Hemorrhage
• Meningitis
• Cerebral Hypoxia
• Stroke
• Dementia
• Alzheimer Disease
• Parkinson Disease
• Multiple Sclerosis
• Compression of spinal
cord and nerve roots
- PIVD
• Bell’s Palsy
• Tumors
LT

139. Thank
you
LT