One body, many parts
A bus comes fast. Your feet stop. Your hand grips the rail. All in one second.
- A bus comes fast.
- Eyes see it.
- A message runs to the feet.
- Another message reaches the hand.
- Both happen in the same second.
Switch the news on and off. See what each part does.
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A body has many parts. Each part has its own job. Legs walk. Hands grip. Eyes watch.
These parts must act together. Each one needs news of the same event, in time. The news is a message to the part. Without it, a part cannot know what to do.
This is coordination: parts working together in step. Each part acts at the right time.
The body uses two systems. The nervous system sends fast signals along nerve cells. Hormones send slower chemical messages through the blood.
The rule
A body has many parts with different jobs. They must act together, not alone. The nervous system and hormones keep them in step.
For example, a goalkeeper's eyes see a shot. If the legs get the message in time, they move. If not, the ball goes past.