Page 281 - New Medley 5 Semester 1

Types of Nerves

Nerves are of three types: Sensory nerves, motor nerves and connecting nerves.

Sensory nerves: These nerves carry signals from the sense organs to the spinal

cord and the brain. These signals convey messages of hotness, cold, smell,
colour, etc.

Motor nerves: These nerves carry commands from the brain and spinal cord

to the muscles and glands. These commands tell the muscles and glands what,
when and how much to do.

Connecting nerves: These nerves pass the messages between sensory nerves
and motor nerves.

Reflex Action

What happens when your finger gets pricked by a thorn while plucking a
flower? You immediately withdraw your hand without even thinking about it.

Such an action that takes place automatically without our thinking is called a

reflex action.
The brain has no role in a reflex action, only the spinal cord takes immediate

decision. For example, if you touch a hot object unexpectedly, the sensory nerves

convey the signal of high temperature (hotness) to the spinal cord. The spinal
cord passes the order to the motor nerves through the connecting nerves. The
motor nerves finally carry instruction to the muscles of the hand to withdraw

it immediately.

Blinking of eyes and jumping off immediately when you accidentally step upon
a sharp edged stone are some other situations showing reflex actions.

1 • Remembering

Name the following.

1. The largest part of the brain
2. The automatic actions controlled by the spinal cord
3. A nerve type that carries message from the nose to the brain

4. A nerve type that carries message from the brain to the eye

279