BOOM! And there it was. Little Adam, who had just been playing invisible pirate, forgot that his foot wasn't invisible. The tip of his big toe crashed straight into the leg of an old wooden chair.
And in that exact second, deep inside Adam's bumped toe, someone tiny, electric, and incredibly fast was born. His name was Impulse. He was no bigger than a spark, but he had a very important mission. In his hand he clutched an urgent message with two red letters glowing on it: OW!
"I must hurry!" whispered Impulse to himself, and without a moment's hesitation he jumped onto the long, glittering path that wound from the toe up the leg. It was the Nerve Highway, the fastest track in all of Adam's body.
Impulse ran as fast as his strength would carry him. The path ahead glowed with a faint light and around him flashed other, much slower signals. The first one he met was a round, soft signal named Touch. He was rolling along the highway like a lazy little ball.
"Hello! Where are you rushing to?" asked Touch in a friendly way. "I'm carrying a message about how pleasant Adam's woolen sock feels."
"I don't have time to chat!" replied Impulse and whizzed past him. "My message is very important! It's an alarm!"
Touch just blinked in surprise and continued his slow rolling. In a moment, Impulse caught up with another signal. This one was warm, spreading along the path like honey, and was called Warmth. He carried a message about the pleasant heat radiating from the slipper.
"Wait a moment, warm yourself up," offered Warmth with a smile. "You're flying like you're panicked. There's nowhere to rush to."
"But there is!" cried Impulse and didn't even slow down. "There's danger! I must warn the Control Center!"
He ran on, through the ankle, around the knee, still up the long, long Nerve Highway. The path was getting busier and busier. Impulse realized that all the signals were heading to one place, but he was by far the fastest of them all. Why?
Just as he was thinking about this, he arrived at a large intersection. It looked like a huge roundabout full of little lights. In the middle stood an old, wise signal named Synapse, who directed all the traffic. He wore a uniform and held a small light baton in his hand.
"Stop!" called Synapse when he spotted Impulse's speed. "What urgent message are you carrying, little one?"
"My name is Impulse and I'm carrying an OW! message from the big toe!" he explained breathlessly. "There's been an accident!"
Wise Synapse looked at him and nodded understandingly. Then he raised his baton and stopped all the other signals – Touch from the sock, Warmth from the slipper, and a weak signal about itching on the calf. Everyone had to wait.
"Messages about warmth and touch are nice," said Synapse loudly so everyone could hear. "They help Adam feel good. But messages labeled OW! are the most important. They're warnings. They protect the body from damage. That's why they always have priority on our highway! Your path is clear, Impulse. Go!"
Impulse felt enormous pride. His work was truly important! He thanked him and set off with new energy on the final stretch of the journey. The Nerve Highway led him to a huge, glowing dome that pulsed with thousands of lights. It was the Control Center. Adam's brain.
He entered and found himself in a huge hall full of busy Controllers sitting at desks processing all the information from the body.
"Urgent message!" shouted Impulse.
One of the Controllers ran up to him, took the message labeled OW! and quickly read it.
"We have pain in the big toe on the left foot! Level: medium. Cause: impact with a hard object!" he announced into the microphone.
The hall buzzed with activity. The Head Dispatcher in the center of the room immediately issued orders.
"First order: pull back the foot! Immediately! Second order: send a signal to the mouth to make a pain sound! Third order: command the eyes to look down at the toe! And fourth, very important order: store in memory the information: 'Watch out for that chair!'"
And outside, in the real world, it all happened in a single moment.
"Owww!" cried Adam and quickly pulled his foot back. He crouched down, looked at his red toe, and began gently blowing on it. He felt the pain slowly subsiding. He looked at the chair and frowned.
"Next time I'll be more careful," he said to himself and cautiously stood up.
Deep inside, in the Control Center, little Impulse contentedly watched how his quick journey had made sense. He had helped Adam. Protected him. The Head Dispatcher approached him and patted him on the shoulder.
"Excellent work, Impulse. Thanks to you, Adam is fine and has learned his lesson."
Impulse smiled. He was just a tiny, invisible spark, but he had just completed the most important mission in the world. And he knew that when needed, he would set off again anytime to protect his Adam.
And maybe even right now, as you read these lines, some Impulse of your own is running along your Nerve Highway to let you know that you should take good care of yourself. Will you try to listen to him sometime?