Download Nervous system

Human Nervous System
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What are we going to learn ?
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Function of nervous system
Parts of nervous system
Types of neurons
Conduction of impulse through neurons
Brain
Spinal cord
Reflex action
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What does the nervous system do?
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Humans perform various activities simultaneously
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For example walking, hearing, seeing …
I can’t
understand
any
of thistask
!! of
The nervous
system
performs the
important
effective coordination and regulation of these activities
How is this jump performed by your body?
Imagine, while crossing a road, you
1. The nervous system collects information about what is happening
observe
busorgans
travelling
towards
through
variousasense
( the eyefast
watches
the bus travelling fast
towards
you,avoid
the ear hears
the sound of
the approaching
you. To
an accident
shouldn’t
you bus, the brain
gets this information and decides that an accident is likely …) :
Coordination jump out of the way?
2.
Decide the appropriate action to be taken ( The brain decides that
jumping out of the way is the best action) : Effective
3.
Send that response to the correct part of the body ( the legs) through the
network of neurons : Regulation
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Parts of the nervous system
Central Nervous System (CNS)
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Peripheral Nervous System
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Function: Regulation of all activities of the body
Two parts
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Brain
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Spinal cord
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Function: Exchange messages between
the CNS and other parts of the body
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Neurons are connected to each other to
form a network
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This network connects the brain and
spinal cord with all parts of the body
Autonomous nervous system
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Consists of neuron network in the heart, lungs,
stomach etc.
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Nerves
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Two types
1. Neurons
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Cells which are capable of generating and conducting
electrochemical impulses
2. Neuroglia
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These support the neurons and supply nutrients to them
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Neurons
• Each neuron has many dendrites
but only one
Dendrites
axon with multiple branches
Synapse : connection
point between two
neurons
• The longest axon in the body is approx. 1 m
Cell body
long!
Nucleus
• The point where two neurons meet
is called a
synapse
• One neuron may have 1000 to 10000 synapses !
• In this manner each neuron connects to multiple
Axon
neurons to form a complex network
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Neurons look like this
Neurons in spinal cord
Neurons in the brain
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The conduction of an electric impulse
in a neuron 1
Neurons carry any sensation received by the sensory organs
(for example: the prick of a pin on a fingertip) to the brain by
means of an electric impulse
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The conduction of an electric impulse
in a neuron 2
A pin prick generates an electric impulse in the first neuron
This impulse is first carried by the dendrite to the
cell body…
Dendrites
…from the axon to the synapse… …from the synapse ndthe impulse is
regenerated in the 2 neuron
Cell body
Nucleus
From the cell body to the
axon …
Synapse
Axon
Synapse
First neuron
In this fashion the
impulse reaches the
brain
Second neuron
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Types of neurons
1.
Sensory
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2.
Motor
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3.
These carry electric impulses from sensory organs to
the brain and the spinal cord
These carry electric impulses from the brain and the
spinal cord to the motor limbs like legs and also to
skin, glands etc.
Associative
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These coordinate between the motor and sensory
neurons in the brain and the spinal cord
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The human brain
The brain helps us
In short we are aware distinguish
The
makes
between
Thesense
brain
helps
us mother’s
of brain
our existence
because
The brain
Weenables
can recall
us the
past
of the
images
affectionate
touch
interpret
what
we
hear
…her
angry smack !
of
our
brain
that
we
see
to because
think of the brain
and...
through
our
ears
through our eyes
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The work of the brain
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Sensory neurons carry sensations to the brain
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Interpreting these sensations and deciding the action
required is done in various parts of the brain
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The impulse of the required action is carried to the
appropriate limb by motor neurons
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The brain helps us think, generates our emotions, defines our
personality, …
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The brain stores innumerable events of the past
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We call this our memory
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The structure of the brain 1
The brain located within the skull
The
brain weighs about 1.4 Kg
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it is protected by the skull made of
bones
 Within the
skull there are three
strong protective layers called as
meninges
 The
space within these layers is
filled with fluid which cushions the
brain from external shocks
 The
brain contains about 10000
crore neurons
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The structure of the brain 2
The three main parts of the brain
1. Fore-brain
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Cerebrum is the main
constituent ü Fore brain
is the
2. Mid-brain
largest and most
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Controls important
movement of eyes,
part of the
the size of the eye lens and
brain.actions
We shall learn
some involuntary
3. Hind-brain more about this later.
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Cerebellum
 Coordinates voluntary activities and helps the
body maintain balance
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Medulla Oblongata
 Controls some involuntary actions like blood
circulation , breathing etc.
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The structure of the brain
External view
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Cerebrum
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Cerebellum
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Medulla
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The structure of the brain
Sectional view
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Cerebrum
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Mid-brain
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Hind brain
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Cerebellum
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Medulla
Spinal cord
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Cerebrum
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The largest part of the brain; Numerous
folds on its surface
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These folds enable accommodation of
maximum neurons in minimum space
Function related to thinking, emotions,
personality, decision making
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Interpret the information received from the
sensory organs
Relate this information to related items stored in
memory and decide how to respond
Convey the response to the appropriate part of
the body
Cerebrum is divided into two equal halves
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The right half controls the left part of the body
and the left half controls the right part of the
body
Top view of the cerebrum
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Regions of the cerebrum that control
various activities of the body
Movement
Sense of
touch
Thought process
Vision
Sense of
taste
Speech
Sense of
smell
Hearing
View of cerebrum from the left side
Cerebellum
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Spinal cord
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The spinal cord is a long
narrow tube made of
neurons
Begins at the medulla: 45
cms long
Protected by the bones of
the spine
Function
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Conducting the impulses
received from sensory organs
to the brain
Routing the motor impulses
received from the brain to the
appropriate organs
Coordinating reflex actions
Spinal cord
Bones of the
spineû
Cartilage disc
between bones
of spinal cord
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Reflex action
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Sometimes the nervous
Pain stimulus
system has to respond
very quickly to external
stimuli
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…and the hand is
pulled back
these neurons decide which
The neuron
pain stimulus
reaches
motor
to activate
for
the
association
neuron
in
the
quick response to the stimulus
spinal cord
Association
neurons
For example, when
your finger touches
the flame of a candle
In such cases response
is given by the spinal
cord without involving
the brain
This is called reflex
action which requires …carried by
sensory
coordination between
neurons
sensory neurons and
motor neurons in the
spinal cord
This coordination is
performed by
association neurons
Motor neuron
Spinal
cord
(cross
section)
Muscle contracts
when it receives the
impulse from the
motor neuron …
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The End
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