Consists of:
1. Brain
2. Spinal Cord
3. Peripheral nerves
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Initiate and/or regulate movement of body
parts.
Regulate secretions from glands.
Gather information about external
environment and internal environment for
maintenance of homeostasis.
Maintain appropriate state of consciousness
Stimulate thirst, hunger, fear, rage and sexual
behavior for survival.
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The Central Nervous System (CNS) includes
the brain and spinal cord.
The Peripheral Nervous System (PNS) made
up of cranial nerves and spinal nerves.
Autonomic nervous system integrates the
activities of visceral structures. It has
elements both in CNS and PNS.
Meninges
 CNS is covered by meninges -made up of three
membranes
1. Piamater-inner most layer, thin and delicate,
follows grooves and depressions closely.
Follows blood vessels that supplies to the
substance of CNS.
2. Arachnoid –middle layer, thin and delicate,
Connected to the piamater layer by filaments
called arachnoid trabeculae. This connection
gives a weblike appearance between arachnoid
and piamater.
Subarachnoid space-Space between arachnoid
and piamater.Filled with CSF-Point of collection
of CSF.
3. Duramater-outermost. Tough and fibrous.
Equivalent to periosteum of the cranial bones.
Forms a transverse and longitudinal folds to
divide two cerebral hemispheres and
cerebellum and cerebrum.
The duramater in spinal meninges is
seperated from periosteum of the vertebral
canal by a fat-filled space-Epidural spaceThis is the site for epidural anaesthesia.
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Enlarged rostral part of cns,
located in cranium
Divided into forebrain, midbrain and hindbrain.
Brain
Forebrain
Midbrain
Hindbrain
Forebrain
 cerebrum, pineal body, thalamus and
hypothalamus.
Midbrain
 small area connecting forebrain and
hindbrain
Hindbrain
 medulla oblongata, pons and cerebellum
Cerebrum: the largest part of the brain
 Divided into left and right hemispheres.
 The hemispheres are covered by a thin layer of
gray matter known as the cerebral cortex
 Divided into four lobes:
1. occipital
2. temporal
3. parietal
4. frontal lobes
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Caudal continuation of medulla oblongata
Runs along the dorsal side of the body
links the brain to the rest of the body.
The gray matter is towards the centre of the spinal
cord consists mostly of cell bodies and dendrites.
The surrounding white matter is made up of bundles
of interneuronal axons (tracts).
Some tracts are ascending (carrying messages to the
brain)
others are descending (carrying messages from the
brain).
Also involved in reflexes that do not immediately
involve the brain.
Made up of
 cranial nerves
 spinal nerves
 Autonomic nervous system.
Functions
 Convey sensory information to the brain and
spinal cord.
 Produce movement of muscles and secretions
from glands via its motor nerves.
Nerve
 A nerve is an enclosed, cable-like bundle of
nerve fibers or axons. Based on its origin a
nerve can be:
1. Cranial
2. Spinal
1.Cranial nerves
 Originate from the brainstem
 Mainly control the functions of the anatomic
structures of the head.
 12 pairs of cranial nerves that originate from
various parts of brain and supply different
sense organs in head.
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Cranial nerves are designated by roman
numerals.
Named from most rostral (I) to most caudal(XII)
Except cranial nerves I (olfactory) and II (optic)
all other cranial nerves arise from mid brain,
pons and medulla oblongata.
Some are strictly motor or sensory unlike spinal
nerves which are mixed.
Spinal Nerves
 Take their origins from the spinal cord.
 The dorsal and ventral roots from spinal cord
fuse close to the intravertebral foramenbecomes mixed type of nerve-Spinal nerves
 A pair of spinal nerve (left and right) emerges
caudal to the vetrebra of same serial number
and name.
 Example- First pair of thoracic nerves
emerges through the space between the 1st
and 2nd thoracic vertebra.
 In cattle, there are 37-39 pairs of spinal
nerves: 8 cervical, 13 thoracic, 6 lumbar, 5
sacral and 5 -7 coccygeal.
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As soon as it emerges from the intervertebral
foramen, spinal nerves divides into a dorsal
branch and ventral branch (both are mixed
type)
Dorsal branch supplies to muscles and skin
that are dorsal to the transverese process of
the vertebrae.
Ventral branch supplies to the the structures
that are ventral to the transverse process of
the vertebra-incuding limbs.
Plexuses-A tangled arrangements of spinal
nerves that supplies to the limbs.
Brachial plexus
 Supplies to each thoracic limbs.
 Formed by a network of nerves derived from
last three crevical and first one or two
thoracic nerves.
 Gives rise to specific named nerves that
supplies the muscles of thoracic limbs and
skin of the same region.
Lumbosacral plexus
 Supplies to each pelvic limbs.
 Formed by a network of nerves derived from
last few lumbar and first two or three sacral
nerves.
 Gives rise to specific named nerves that
supplies the muscles of pelvic limbs and skin
of the same region.
Functional unit
 Neuron or a nerve cell is an anatomic and
physiologic unit of nervous system.
 Made up of cell body and processes dendrites
and axon.
 A process is called dendrite if it carry impulse
towards cell body and an axon if it carry
impulses out of cell body.
 Axon is called nerve fiber and membrane
covering the axon is called axolemma
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In a myelinated axon axolemma is
surrounded by myelin sheath called
neurilemma
At regular interval there is myelin free gaps
called nodes of Ranvier that facilate faster
conduction of impulses.
A group of nerve cell bodies in CNS (brain
and spinal cord) is called nucleus while group
of nerve cell bodies outside CNS is called
ganglion.
Bundle of neuron fibers within the CNS is
called a tract while bundle of neuron fibers
outside CNS is called nerve.
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Figure A
Figure B
Synapse
 Junction between two nerve terminals is
called synapse.
 No physical contact between the neurons
instead.
 There is space in between, across which
impulse is conducted through chemicals.
Impulse conduction
 Three stages
1. Resting potential
2. Depolarization
3. Repolarization.
Resting potential
 The maintenance of relative negative inside
the cells. Maintained by continuous exit of Na
ions and active transport of Na ions by Napump.
 Stimulation nerve either physically or
chemically will result in change in the ion
concentration.
Nerve
cell
+++++++++++++++++
- - - - - - - - - - -_
- - - - - - - - - - - - - - - - +++++++++++++++ ++
2. Depolarization
 Chemical or physical stimulation of nerve cell
increases the membrane permeability to
positive ion (Na +) at the point of stimulation.
 As a result the positive ion rushes into the
cell.
 This reverses the membrane potential at the
point of stimulation and it becomes positive
on inside and negative on outsidedepolarize.
Stimulus
++++++++-+++
- - - - - - - +--- - - - - - +- -++++++++ -+++
3. Repolarization
 Ions return back to its normal position
starting at the initial start point.
 While depolarization proceeds along the
length of neuron the repolarization follows
almost instantly.
 Repolarization process sets the membrane
potential back to normal resting membrane
potential.
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On completion of these three actions the
nerve impulse has been conducted along the
length of a neuron.
Same process occurs along the length of
next neuron.
Impulse across the synapse is conducted by
release of chemical from the terminal bulb of
the first neuron and picked up by the
dendrites of the second neuron and impulse
generated.
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The organs (the "viscera") of our body, such
as the heart, stomach and intestines, are
regulated by a part of the nervous system autonomic nervous system (ANS).
Controls many organs and muscles within the
body.
Functions in an involuntary, reflexive manner.
The ANS is most important in two situations:
 In emergencies that cause stress and require us
to "fight" or take "flight" (run away)
 In non-emergencies that allow us to "rest" and
"digest" .
The ANS is divided into two parts:
1. The sympathetic nervous system
2. The parasympathetic nervous system
1.The sympathetic nervous system
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Arises from thoracic and lumbar segment of
spinal cord.
Prepares body for “Fight or flight” response.
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In these types of situations, your sympathetic
nervous system is called into action - it uses
energy - your blood pressure increases, your
heart beats faster, and digestion slows down.
The parasympathetic nervous system
 Arise from cranial nerves and sacral segment of
spinal cord.
 Facilitate “Rest and Digest” response of the
body.
 Parasympathetic nervous system to work to
save energy - your blood pressure decreases,
your heart beats slower, and digestion can
start.
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seizure: A seizure is a sudden occurrence of
abnormal, uncontrolled electrical activity in
the brain resulting in unwanted and
uncontrolled activities of muscles/organs.. A
Epilepsy:condition of recurring seizures is
spasm: Spasm is a general term for a sudden
involuntary muscle movement.
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Myelopathy-Disease effects on spinal cord
Encephalopathy-Disease effects on CNS.
Encephalitis-Inflammation of brain.
Meningitis-Inflammation of meninges.
Neuritis-Inflammation of neurons.
Ataxia-loss of coordination and resulting
imbalance.
cerebral thrombosis - the most common type
of brain attack; occurs when a blood clot
(thrombus) forms and blocks blood flow in an
artery bringing blood to part of the brain.
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chorea - rapid, jerky, dance-like movement
of the body.
computed tomography scan (CT scan) - a
diagnostic imaging procedure that uses a
combination of x-rays and computer
technology to produce cross-sectional
images of body.
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Electroencephalogram (EEG) - a procedure
that records the brain's continuous, electrical
activity by means of electrodes attached to
the scalp.
Palsy - paralysis of a muscle or group of
muscles
Hemiplegia- paralysis of one quarter of the
body.
Quadriplegia-Paralysis of all the four limbs.
Epidural Anaesthesia:
Introduce anaesthetic into epidural space.
Brings about anaesthesia of the caudal parts of the
body.
In bovines given between first and second caudal
vertebrae.
Used for surgical procedures like-caesarian,
correction of prolapse.
Obturator nerve paralysis
 Condition where an animal cannot get up
after giving birth.
 Occurs mostly in primipara animals.
 The obturator nerve passes through the spine
of the pelvis.
 Forcinf of fetus through the pelvis injures the
obturator nerve and results in paralysis.