The document summarizes the main components and functions of the human nervous system. It describes the brain as the control center made up of the cerebrum, cerebellum, and brain stem. The spinal cord connects the brain to nerves throughout the body and is responsible for involuntary movements. There are sensory nerves that carry signals to the brain and motor nerves that carry signals from the brain. The five senses - sight, hearing, smell, taste, and touch - allow humans to perceive their environment through specialized sense organs like the eyes, ears, nose, tongue, and skin.

1. NERVOUS
SYSTEM

2. Nervous system– The system that controls all the movements or activities of the
body through signal transmission
Brain – Walnut shaped organ which is protected by the skull Centre of control for
all body activities Provides memory
The three sections of the brain include: Cerebrum Cerebellum Brain stem

3. Cerebrum Largest section of the brain Helps to think Responsible for thoughts,
memory, speech, intelligence and learning Controls the sense organs Human
cerebrum is big which provides them with intelligence

4. Cerebellum Located below the cerebrum at the back of the head Controls muscle
movements Maintains body balance

5. Brain stem Lower section of the brain connecting it to the spinal cord
Responsible for involuntary movements like swallowing, breathing and circulation

7. Spinal cord– Thick bundle of nerves linked to the brain stem Runs down the back
of the body and is protected by the vertebral column Nerves arise from the spinal
cord and runs throughout the body forming a network

8. Nerves – Bundle of fibres carrying signals from the organs to the brain and spinal
cord, and again taking back signals to the organs

9. Sensory nerves Nerves carrying signals from the sense organs to the brain and
spinal cord Brain helps in perceiving these signals giving us senses Provides
only one directional movement of signals

10. Motor nerves Nerves carrying signals from the brain and spinal cord to the rest of
the organs leading to a response Provides only one directional movement of
signals

11. Mixed nerves Acts as both the sensory and motor nerve Present in the brain and
spinal cord Allows two directional movement of signals

12. Reflex action– A fast and automatic reaction Signals do not reach the brain
Spinal cord receives the signals and ensures action or response Eg: blinking
when something enters into the eye, withdrawing of hands on touching a hot
object

14. Sense organs Humans have five senses which include: Sight Hearing Smell
Taste Touch

15. EYE

16. Eyes – The sensitive ball-like organ which gives us the ability to see things
Coordination of the brain and eyes provide sight
Fitted in the socket of the skull and is protected by the eyelids from dust and
bright light Able to recognise and differentiate colours, shapes, size, distance of
things
Iris is the coloured part of the eye
Pupil at the centre of iris allows the passage of light
Lens at the back of the pupil focuses the light on to the retina
Images of objects are formed on the retina Retina can recognise light and colour
due to the sensitive cells present in it
Optic nerve carries the information about the object to the brain

17. Ears – The organ which helps us in hearing The outer funnel-like part of the ear is
the external ear which collects sound Eardrums get struck by sound waves and
start vibrating The vibrations reach the inner ear after passing through the three
bones in the middle ear The sound waves convert to signals and is carried by the
nerves to the brain

18. Nose – The organ which provides us with the sense of smell The molecules of a
scent enters the nose The nerve endings detect this scent and send signals to the
brain Brain receives the signal and helps us to know what scent it is

19. Tongue – The organ which helps us to differentiate between the four kinds of taste
Helps us in tasting Consists of tiny buds known as taste buds The nerve endings
in taste buds detects the four kinds of taste that are sweet, sour, salty and bitter
The signals reach the brain and we can taste food

20. Skin– The outer layer of the body which makes us able to feel things by touching
them Covers the entire length of the body and protects it from injury, dirt and germs
Skin has nerve endings for sensing pain, pressure, heat, touch and cold Fingertips
are more sensitive than other parts of the skin due to the presence of more number
of nerve endings.

21. A PRESENTATION BY DIVYA KUMAR