Nervous system part 1

Nervous System Part 1
• Presented By –
• Prof.Dr.R.R.Deshpande
(M.D in Ayurvdic
Medicine & M.D. in
Ayurvedic Physiology)
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Introduction to Nervous system
• 2 main types of nervous system
• Central nervous system (CNS) & Peripheral
nervous system (PNS).
• CNS consist of brain & spinal cord.
• CNS is connected to sensory receptors, muscles
& glands through PNS.

Nervous System

Introduction to Nervous system
• PNS consist of cranial nerves & spinal
nerves.
• PNS is divided into somatic nervous
system (SNS) & An Autonomic nervous
system (ANS).
• ANS has 2 branches that is sympathetic
& parasympathetic

Histological aspect
• Nervous system consist of 2 types of cells
that is neurons & neuroglia.
• Neurons or nerve cells convert stimuli into
nerve impulses or nerve action potentials.
• These impulses are carried to other
neurons, muscle tissue or glands.
• Neurons consist of a cell body & 2
processes, Dendrites & Axons

Neuron

Histological aspect
• Cell body contains nucleus & other
organelles.
• Dendrites are highly branched.
• They are major receiving portion.
• The axon is a single thin, cylindrical
process, which is very long & conducting
nerve impulses towards another neuron
or other tissue.

Histological aspect
• Neurons perform special function of nervous
system like understanding sensations, thinking,
remembering, controlling muscle activity &
regulating glandular secretions.
• Neurogli support, nurture & protect the
neuron.
• They maintain homeostasis of the fluid which
bathes the neurons

Histological aspect
• When nervous tissue is damaged
regeneration is not possible.
• Malignant brain tumours are commonly
derived from neuroglial cells, & called as
gliomas.

Types of neuroglia
• Amongst 6 types following 4 types are
found in the CNS.
• 1) Astrocytes - they participate in the
metabolism of neurotransmitters,
participate brain development & form
blood - brain barrier (BBB).
• 2) Oligodendrocytes - produce myeline
sheath around axons of neurons of CNS

Types of neuroglia
• 3) Microglia - these are phagocytic cells.
• 4) Ependymal cells - line the ventricles &
spinal canal.
• They form CSF & also help in circulation
of CSF.

Neuroglia of PNS
• Shawn cells - produce myeline sheath
around PNS neurons.
• Satellite cells - support the neurons in
ganglia of PNS.

Myelination
• The axons are surrounded by a multilayered
lipid & protein covering, produced by neuroglia
& called as myelin sheath.
• At intervals along an axon, the myeline sheath
has gaps, called as Nodes of Ranvier.
• These nodes increases the speed of nerve
impulse

Neuron
• Some neurons are tiny while others are
the longest cell.
• Nerve impulses travel with a speed
ranging from less than 1 to more than 100
meters/sec.
• Site of functional contact between 2
neurons or between a neuron & muscle or
gland is called as a Synapse

What are Nisselles bodies ?
• Nisselle bodies are chromatophilic
substance in the cytoplasm of neuron.
• This is rough endoplasmic reticulum,
which is the site of protein synthesis.
• These proteins are used for growth of
neurons & regeneration of damaged
peripheral nerve axons.

Classification of neurons
• 1) Multipolar neurons - several dendrites
& 1 axon (present in brain & spinal cord)
• 2) Bipolar neurons - 1 dendrite & 1 axon
(Present in retina of the eye, inner ear &
olfactory area of the brain)
• 3) Unipolar neurons - only 1 process,
extending from cell body & these are
always sensory neurons.

Functional classification of neurons
• 1) Sensory or afferent neurons, which
transmits sensory nerve impulses from
receptors in the skin, sense organs,
muscles, joints & viscera in to the CNS.
• 2) Motor or efferent neurons convey
motor nerve impulses from the CNS to
effectors

Functional classification of neurons
• 3) Association neurons or inter
neurons - neurons other than sensory or
motor are called as inter neurons.
• They contribute 90% from total neurons
examples of association neurons are
Purkinje cells in the cerebellum or
Renshaw cells in the spinal cord

Mechanism of propagation of
nerve impulse
• Neuron impulse is also called as neuron
action potential (AP).
• This is a sequence of rapidly occurring
events, which causes depolarization &
again repolarization

Details of action potential
• For action potential to takes place, voltage
gated Na+ & K+ channels open in
sequence. Membrane polarity changes
from - 70 to +30mV.
• This is depolarization & then during
repolarisation, resting membrane potential
again changes from +30 to – 70mV.

Details of action potential
• During the refractory period, another
impulse cannot be generated.
• Impulse can be generated only through
supra threshold stimulus.
• Impulse or action potential travels from
point to point along the membrane &
hence it is useful for long distance
communication

All or none principle
• If a stimulus is strong to generate an
action potential, the impulse travels at a
constant & maximum strength, for the
existing condition.
• A stronger stimulus will not cause a larger
impulse

Saltatory conduction
• Here nerve impulse leaps from neurofibral
node to node.
• Fibers with larger diameters or
myelinated fibers conduct impulses
faster than fibers with smaller diameter or
unmyelinated fibers.
• The intensity of stimulus is coded in the
frequency of action potential.

Synapse
• Synapse is the junction between neuron
& another or between neuron & muscle
or gland.
• Electrical & chemical are the types of
synapses.
• At a chemical synapse there is only one
directional transfer from presynaptic
neuron to postsynaptic neuron

Synapse

Synapse
• Excitory neurotransmitter depolarize the
postsynaptic neurons membrane.
• An inhibitory neurotransmitter
hyperpolarizes the membrane of post
synaptic neuron.

Synapse
• The postsynaptic neuron receives signals,
integrates them & then responds.
• Important neurotransmitters are acetylcholine
( Ach) , Gamma aminobutyric acid (GABA),
epinephrine, dopamine, nitric oxide.
• A neuron’s chemical & physical environment
affect impulse conduction & synaptic
transmission.

What is the role of
nervous system ?
• 1) To respond in a coordinated manner to
environmental changes.
• 2) To co - ordinate, control different
movements. (Muscular, secretomotor etc.)
•
• 3) Prolong the life by protecting the body
against harmful stimuli

Nervous System

12 Cranial Nerves

31 Pairs of spinal nerves
• 8 Cervical +
• 12 Thoracic +
• 5 Lumbar +
• 5 Sacral +
• 1 Coccygeal

Spinal Nerves

Spinal Cord

Spinal Nerves

Parts of the Brain

Parts of the Brain
• i) Fore brain - Cerebrum, Thalamus,
Hypothalamus
• ii) Mid brain
• iii) Hind brain - Pons, medulla, cerebellum
•
• (Brain stem = mid brain + Pons + medulla)
• Lobes of cerebrum - Frontal, Parietal,
Occipital, Temporal.

Brain Parts

Functions of Brain

Cranial Nerves

Cranial Nerves –
Anatomical sites

Cranial Nerves

Functions of Cranial Nerves

Neuron
• Structurally, the nervous system consists of
Neuroglias & Neurones.
• Neuroglias are the supporting cells with less
physiological importance with regards to
nervous system.
• Neurons are the nerve cells with all its
branchings.
• A neuron is taken as the functional unit of
nervous system.

Properties of nerve fibers
• 1) Excitability
• 2) Conductivity
• 3) All or none law
• 4) Refractory period
• 5) Summation
• 6) Adaptation

Classification of nerve fibers
• 1) Medullated & nonmedullated
(Histologically)
•
• 2) Motor & Sensory (Functionally)
• Adrenergic = producing adrenaline &
cholinergic = producing acetylcholine
(Chemically).

Reflex (Definition)
• Reflex action is an involuntary motor
response due to a sensory stimulus.
• 3 types –
• 1) Superficial
• 2) Deep
• 3) Visceral

Superficial Reflexes

Deep Reflexes

Visceral Reflexes
• Autonomic
• 1) Deglutition
• 2) Defecation
• 3) Micturition
•
• 4) Pulmonary & Gastrointestinal reflexes.

1) Spinal cord
• Spinal chord is a downward continuation
of medulla oblongata extending from the
first cervical to first lumber vertebrae.
• The tail ends at 2nd sacral.
• It gives out 31 pairs of spinal nerves.

Spinal Nerves
• Each nerve is made up of posterior
(Sensory) & anterior (Motor) roots.
• Spinal cord is symmetrically divided into 2
lateral halves by means of 2 median
raphes (Anterior & posterior)

Functions of pyramidal tract
• 1) Chief pathway of voluntary
movements.
• 2) Possibly form a part of the pathway for
superficial reflexes

Functions of Extra pyramidal tracts
• 1) Cortico - nuclear fibres control the movements
of the eye - ball.
• 2) All the tracts are collectively responsible for
tone, posture & equilibrium.
• 3) They control complex movements of the body
& limbs such as coordinated movements of
arms & legs during walking.

Functions of Extra pyramidal tracts
• 4) The cortex exerts tonic inhibitory
control over the lower centres through
these tracts.
• 5) When pyramidal tracts are damages,
the extra pyramidal tract may carry the
volitional impulses to some extent.

2) Medulla Oblongata
• Upward continuation of the cord, Medulla
Oblongata, forms a pathway for ascending &
descending tracts.
• The nucleus of 4, 5, 6 & 7 cranial nerves are
located in this region.

Medulla oblongata

2) Medulla Oblongata
• The importance of Medulla Oblongata lies
in the location of the centers performing
vital functions.
• eg. - Respiratory centre, Cardiac centre,
Vasomotor - deglutition - vomiting - sweat
secreting centre & sugar regulating centre.

3) The Pons
• Lies between Medulla (below) & mid -
brain (above) with cerebellum on each
side.
• The Pons is superior to Medulla. It
connects the spinal cord with the brain &
links parts of the brain with one another
by way of tracts.

3) The pons
• It relays nerve impulses from the cerebral
cortex to the cerebellum.
• It contains the nuclei for cranial nerves 5,
6 & 7 & the vestibular branch of 8.
• The reticular formation of the pons
contains the pneumotaxic & apneustic
centers, which help to control respiration.

Cerebellum
• The Cerebellum occupies the inferior &
posterior aspects of the cranial cavity.
• It consists of 2 hemispheres & a central
constricted vermis.
• It is attached to the brain stem by 3 pairs
of cerebellar peduncle.

Cerebellum

Cerebellum
• The Cerebellum functions in
• The co - ordination of skeletal muscles
& the maintenance of normal muscle
tone & body equilibrium.

4) Mid - brain
• Upward continuation of medulla. Through
it passes the aqueduct of Sylvius.
• The cranial nerves except 1st & 2nd
originate or terminate in nuclei situated in
floor of 4th ventricle or floor of cerebral
aqueduct.

12 pairs of cranial nerves

5) Thalamus -- Functions
• 1) Acts as relay station for the sensory
impulses, which are received here, codified &
then transmitted onto respective cortical areas.
• 2) Acts as a centre for conscious sensations.
•
• 3) Control of muscle tone & movements from the
cerebellum also is through latero ventral nucleus
of thalamus.

5) Thalamus – Functions
• 4) The area for sexual perception is also
present in the thalamus.
• 5) The reticular & intralaminar nuclei in the
thalamus are associated with reactions of
alertness of wakefullness.
• 6) Also acts as reflex centre for somatic &
visceral manifestation of emotions etc

Thalamus

6) Hypothalamus - Functions
• The Hypothalamus is inferior to the thalamus.
• It controls & integrates the autonomic
nervous system
• Receives sensory impulses from viscera
• Connects the nervous & endocrine systems
• Secretes a variety of regulating hormones, co -
ordinates mind - over body phenomena

Hypothalamus

Hypothalamus Pituitary Axis

6) Hypothalamus --Functions
• Functions in rage & aggression
• Controls body temperature
• Regulates food & fluid intake
• Maintains the waking state & sleeping
patterns
• Acts as a self sustained oscillator that
drives biological rhythms

Cerebrum
• The Cerebrum is the largest part of the brain.
• Its cortex contains convolutions, fissures & sulci.
• The cerebral lobes are named as the frontal, parietal,
temporal & occipital.
• The white matter is under the cortex & consists of
myelinated axons running in 3 principle directions.
• The Basal Ganglia (cerebral nuclei) are paired
masses of gray matter in the cerebral hemispheres.

Cerebrum

Cerebrum
• They help to control muscle movements
• The Limbic System is found in the
cerebral hemispheres & diencephalon
• It functions in emotional aspects of
behavior & memory
• The sensory areas of the cerebral cortex
are concerned with the interpretation of
the sensory impulses.

Cerebrum
• The motor areas are the regions that govern
muscular movement.
• The association areas are concerned with
emotional & intellectual processes
• Brain waves generated by the cerebral cortex
are recorded as an electroencephalogram
(EEG)
• It may be used to diagnose epilepsy, infections
& tumors

Physiology of motor pathways
• UMN & LMN (Upper motor neuron &
Lower motor neuron)
• 1) UMN - First Neurons in motor pathway
which end on anterior horn cells.
• 2) LMN - Last Neuron in Motor pathway,
which directly supply muscle.
• UMN are having Inhibitory Influence on
LMN

UMN & LMN

Descending Tract or Motor Tract
• From brain to the extremities. Movement of hands &
legs.
• 1) Practical importance of this tract
• i) In 1st year B. A. M. S., clinical hammer is used to test
the deep reflexes. These reflexes are altered due to the
pathology at the spinal cord level or at the brain level.
• ii) In the practice, all the cases of paralysis or
Hemiplegia, the doctor should understand that the
problem is in the Motor tract & not in the sensort tract

Descending Tract or Motor Tract
• 3) Mainly 2 types of the Motor pathway
are as follows
• i) Pyramidal tract or cortico - spinal tract
• ii) Extra pyramidal tract (This path starts
from subcortical area)

Cortico - Spinal Tract (Descending Tract)

Functions of cortico spinal Tract
• i) Voluntary movements are controlled
• ii) Especially skilled movements of distal
joint (writing, painting)

Names of extra-pyramidal tract
(sub-cortical motor area to spinal cord)
• i) Reticulo - Spinal tract
• ii) Vestibulo - Spinal tract
• iii) Rubro (Mid brain) - Spinal Tract
• iv) Olivo (Medulla) - Spinal Tract
• v) Tecto (Mid brain) - Spinal Tract

Functions of Extra pyramidal tract
• i) Controls gross postural movements of
proximal joints
• ii) Regulation of muscle tone
• iii) They can control voluntary movements
if Pyramidal tracts are damaged.

Autonomic nervous system (ANS)
• The system was originally named autonomic
because, previously, physiologists thought that,
it functions with no control from CNS i.e. -
autonomous or self - governing
• But today, it is known that the ANS is neither
structurally, nor functionally independent of CNS
• It is regulated by centers in the brain in
particular by the cerebral cortex, hypothalamus
& medulla oblongata.

ANS -- Structures
• The ANS consists of visceral efferent neurons
organized into nerves, ganglia & plexuses. It is
considered mostly of motor type
• All autonomic axons are efferent fibers. Efferent
neurons are pre ganglionic (with myelinated
axons) & Post ganglionic (with unmyelinated
axons).

ANS -- Structures
• The ANS consists of 2 principle divisions
• Sympathetic (Thoraco - Lumbar)
• Para sympathetic (Cranio - sacral)

ANS -- Structures
• Autonomic ganglia are classified as
• Sympathetic trunk ganglia (On both sides
of spinal column)
• Pre - vertebral ganglia (anterior to spinal
column)
• Terminal ganglia (near or inside visceral
effectors)

Physiology of ANS
• Autonomic fibers release neurotransmitters at
synapses
• On the basis of neurotransmitter produced,
these fibers may be classified as cholinergic or
adrenergic

Physiology of ANS
• Cholinergic fibers release acetylcholine
(Ach). Adrenergic fibers produce nor -
epinephrine (NE)
• Ach interacts with Nicotinic receptors on
postganglionic neurons & Muscarinic
receptors on certain visceral effectors.

Physiology of ANS
• NE interacts with Alpha Receptors on
visceral effectors
• Epinephrine generally interacts with alpha
& beta receptors on visceral effectors.

Physiology of ANS
• Sympathetic responses are widespread
& concerned with Energy Expenditure.
• Parasympathetic responses are
restricted & concerned with Energy
restoration & Conservation

Physiology of ANS
• The parasympathetic division is primarily
concerned with activities that conserve &
restore body energy during times of rest or
recovery of the body.
• It is an energy conservation - restorative
system..

Physiology of ANS
• Activation of the sympathetic division sets
into operation a series of physiological
responses collectively ----
• Called the Fight or Flight Response.

ANS - Control by Higher Centers
• The Hypothalamus Controls & integrates
the autonomic nervous system
• It is connected to both the sympathetic &
the parasympathetic divisions
• Bio - feedback is a process in which
people learn to monitor visceral functions
& to control them consciously

• It has been used ----
• To control the heart rate,
• Alleviate migraine headaches
• Make childbirth easier

• Current therapeutic applications of B io -
feedback include treatment of ----
• Asthama, Raynaud's disease,
Hypertension, Gastrointestinal disorders,
Fecal incontinence, Anxiety, Pain &
Neuromuscular rehabilitation following
Cerebrovascular accidents (CVAs)

Sympathetic & Parasympathetic

Sensations
• What are sensations ?
• Sensations are feelings aroused by
change of environment.
• Classification
• 1) General Sensations - superficial, deep,
visceral
• 2) Special Sensations - Hearing, Vision,
Taste, Smell.

Definition of tract
• A tract may be defined as a bundle of
fibers carrying one or a group of motor or
sensory impulses in the C.N.S.

1) Hearing - Anatomy

Properties of sound
• Pitch, loudness, quality. (The unit of loudness
is called decibel)
• Faintest audible sound - 0 decibel
• Whisper at 4 ft. - 20 D
• Average office = 40 D
• Noisy street 60 - 80 D
• Limit of endurance = 130 D !
• Range of hearing = 20, 000 to 25, 000 vibrations
/ sec.

Ear

Ear
• Tympanic membrane amplifies the sound
22 times
• Audiometry - The instrument to check the
hearing problem.
• Inj. streptomycin given in T.B. causes
impaired hearing in aged patients.
• Due to air pollution degeneration of cilia
take place.

Structure of Cochlea

Organ of corti

Auditory Pathway

1) Main causes of deafness
• 1) Congenital ( Dumb & Deaf)
• 2) Traumatic injury
• 3) Side effect of drug - (Injection
streptomycin for T. B.)
• 4) Sound pollution (Traffic police,
industrial worker, - damage to the cilia of
the cells in the organ of Corti)

2) Important functions of
Middle ear
• i) Impendeance matching = AC > BC
• AC - Air conduction
• BC - Bone conduction
• ii) Tympanic membrane, amplifies the sound 22
times, to overcome the inertia of cochlear fluid
(Perilymph & Endolymph).

Middle ear
• iii) Attenuation Reflex
• This is protective reflex against the loud sound
to avoid the damage to cochlea
• When loud sound waves hit on tympanic
membrane, Tensor Tympani & stapedius muscle
undergo reflex contraction. Ossicular chain is
made rigid. Excess movement of foot plate of
stapes is avoided & cochlear damage does not
take place

Middle ear
• iv) Sound waves after vibrating ossicular
chain in the middle ear, reach to oval
window. It then passes through cochlea
from oval window, towards round window
through perilymph.
• vi) Cochlea is 3 - dimensional tube with 3
cavities & 2 membranes. The apex is
called as ‘Helicotrema

Auditory Path way
• Sound waves create the up & down
movements of basilar membrane. On basilar
membrane, sound wave frequencies are coded
from 20 HZ to 20, 000 HZ.
• Basilar membrane can identify the specific pitch
of sound. This is called as ‘Place principle’.
• Reissner’s membrane, do not have the
“Receptors” for sound wave.

vi) Organ of Corti
• This is responsible for acceptance of
sound waves & transmission of these
waves to cochlear nerve
• Organ of corti are present in basilar
membrane
• Organ of corti is consist of outer & inner
hair cell.

vi) Organ of Corti
• Hair cell or cilia do the friction on
Tectorial membrane & Neurotransmitter
GABA is liberated from hair cell
• GABA = Gamma Amino Butyric Acid
• Due to depolarization, 8th cochlear nerve
is stimulated

3) Cochlear nerve &
transmission of auditory impulse.
• i) Cochlear nerve starts from organ of corti
• ii) From organ of corti up to the pons = 1st
order Neuron
• iii) From pons up to the midbrain = 2nd order
Neuron
• iv) From midbrain up to the thalamus = 3rd
order Neuron.
• v) From thalamus up to the temporal lobe of
the cortex = 4th order Neuron

4) Important locations
in the pathway & their position

5) Names of crossings of fibers
• i) Trapezoid commissure (Pons)
• ii) Commissure of Probst (Midbrain)
• iii) Inferior colliculus commissure
(Midbrain)

6) About the centers
• i) Primary auditory centers (Area 41, 42)
• Situated in superior part of temporal lobe
near lateral cerebral sulcus
• These centers give information about
basic characteristic of sound (Pitch &
Rhythm)

6) About the centers
• ii) Auditory association areas (Area 21, 22)
• They are situated inferior & posterior to primary
auditory area. These centers determine
• a) Whether the sound is speech, music or song.
• b) It also gives the information about the
meaning of speech by translating works into
thoughts.

Applied part –
2 types of deafness
• a) Conductive deafness
• Interference with the passage of sound
waves through the external & middle ear
• b) Nerve deafness
• Interference of transmission of impulses
by the auditory nerve.

Tests of hearing
• 1) Rinne's test
• 2) Weber's test
• 3) Scwabach’s Test

Prof.Dr.R.R.Deshpande
• Sharing of Knowledge
• FOR
• Propagating Ayurved
6/2/2016 149Prof.Dr.R.R.Deshpande

Nervous system part 1

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