Fast and slow, side by side
Show on a big screenA doorbell rings once and stops. Festival lights glow for hours. A nerve signal is brief, like the bell. A hormone often lasts, like the lights.
Pick a job. Switch the path. Compare the time.
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The rule
Nerves are usually fast and reach one place. Hormones are usually slower and reach many places, and some last longer. Each fits jobs the other does badly.
| Feature | Nerves | Hormones |
|---|---|---|
| Speed | Fast, almost at once | Slower than a nerve |
| Reach | Cells joined by nerves | Target cells anywhere, through the blood |
| Duration | Brief | Often longer |
| Best job | This place, right now | Many parts, for a long time |
A nerve reaches only the cells it is joined to. Blood goes to every part. So a hormone can reach cells far from its gland. Only its target cells respond.
Plants have no nerves. They respond with chemicals. Most plant responses come from growth, which is slow.
For example, a hand pulls off a thorn at once. That is a nerve's job. A change that takes weeks is a hormone's job.
Try the lab to finish this lesson.