Page 34 - Future Stars Science Explorer-5

Nerves are made up of bundles of fibres that carrying thousands of messages
every second. The brain is directly connected to the head and neck by
nerves. The rest of the body parts are connected to the brain by nerves

through the spinal cord.

There are three types of nerves.

Sensory nerves : These nerves carry messages from the sense organs to the
spinal cord. These messages are interpreted by the brain and we are able to

see, hear, smell, taste and feel.

Motor nerves : These nerves carry instructions from brain or the spinal cord
to the muscles or glands. These instructions result in movement of muscles or

secretion by glands.

Mixed nerves : These nerves perform both the above functions. They carry

messages to the brain as well as carry orders from the brain to other parts of
the body.

Reflex Actions

Some body movements are done automatically without thinking about
them. This automatic response of body to an event is called a reflex action.
The reflex action involve only the nerves and spinal cord.

For example, our mouth gets watered at the
sight of ice creams and chocolates. Similarly, The spinal cord orders
to withdraw the hand
the action, such as moving our hand away immediately (response).
from a thorn or needle takes place without the

message going to the brain.
A thorn is
The reflex action allows a fast reaction. In pricked (event).

reflex action, on touching the thorn or The message is
carried to the
needle, the nerves send a message to the spinal cord through
spinal cord and the spinal cord orders the the nerves.

hand to withdraw immediately.

The Sense Organs

Sense organs are windows to the outside world. They make us aware of our

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