Responding to change
You need to know what is going on in the world around you. Your nervous system makes this possible. It enables you to react to your surroundings and coordiante your behaviour.
Your nervouse system carries signals (impulses) which travel fast - from 1 to 120 metres per second. This means you can react to changes in your surroundings very quickly indeed.
Hormones are chemical substances. They control many of the processes happening inside the body. Special glands make and realse (secrete) these hormones into your body. Then the hormonses are carried arround the body to their target organs in the bloodstream. They can act very quickly, but often their effects are quite slow and long lasting.
The nervous system
Your body is sensitive to changes in the world around you. Any changes are known as stimuli and they are picked up by cells called receptors. These receptors are usually found clustered together in special sense organs, such as your eyes and your skin…