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

 

ü Nerves are the thread-like structures.

ü They present in the entire body .

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

ü The nerves used to transfer messages .

 

 

Voluntary  and  involuntary  actions

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

ü Walking, dancing, reading, etc…..

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

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

 

Reflex action

µ  A quick response to a stimulus is called a reflex action.

µ 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 .