Nervous System CLASS-5 SIMPLIFIED NOTES

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CHAPTER – 8

Our  Nervous  System 



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What is Nervous System ?

·      The nervous system is made up of the brain  , spinal cord and a vast network of nerves .

·      The nervous system helps the body to perform all its functions .

·      The nervous system controls every movements of the body and the working of all the organs .

·      Controls overall the functioning of the body like memory , speech , heartbeat , breathing ,etc ….

 

About Brain

 

Ø The brain is the soft and delicate part of the body within the skull.

Ø The space between the brain and the skull bones is filled with a fluid.

Ø The fluid protects the brain from jerks.

Parts of brain     

 

    Cerebrum : the cerebrum is the largest and the uppermost part of  the brain . It helps you to think, remember and learn. It also controls the functions of the eyes and ears, nose and tongue .

 

2.       Cerebellum :  the cerebellum controls movements and maintains the balance of the body .

 

3    Medulla :  The medulla is the lowermost part of the brain .  The medulla regulates functions such as heartbeat, circulation of the blood and breathing.

 

About Spinal cord

 

v      The spinal cord links the brain and the other parts of the body . It begins at the medulla of the brain and extends all along the back .

v      The spinal cord is protected inside the vertebral column that is made up of 33 bones called vertebrae.

 

About Nerves

 

ΓΌ Nerves are the thread-like structures.

ΓΌ They present in the entire body .

ΓΌ Nerves are connected either with the brain or the spinal cord .

ΓΌ The nerves used to transfer messages .

 

 

Voluntary  and  involuntary  actions

ΓΌ An action that is controlled by an individual is called voluntary actions.

ΓΌ Walking, dancing, reading, etc…..

ΓΌ An Action that does not have any control by an individual is called involuntary actions.

ΓΌ  Example – breathing, digestion of food , beating of heart  and formation of urine .

 

Reflex action

Β΅  A quick response to a stimulus is called a reflex action.

Β΅ When u touches the hot water, u feel pain. A sensory nerve in your finger senses the pain and quickly carries the message (impulse) to the spinal cord.

The spinal cord too acts quickly. It sends back a message to the arm muscles to move the arm away.

This is the reflex action .

 

How do sense organs work ?

      I.            Eyes – Each eyes has a lens . when we look at an object, the light passes through the lens and the image form inside the eyes . The image is converted into a message or impulse.

   II.            Ears – we hear through the eardrum

 that is inside the ear which is a thin membrane.

 

III.            Nose – We smell with our nose. The nerves inside the nose pick up the smell , convert it into a message and carry it to the brain . the brain recognises the message and helps us know the smell.

 

IV.            Tongue – the tongue has taste buds, which sense different tastes. The taste buds are connected to nerves .

  V.            Skin – we feel when something touches on  the skin . the skin is richly supplied with the nerves  .It helps us to sense pan , temperature  and feel things .


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