Explain · Like I'm five version
Reflex actions in terms of a fire alarm
Is your body like a building with a loud fire alarm inside that shouts for help before you even notice there is a problem?
Reflex actions are very quick moves your body makes to keep you safe from harm. Think of your nerves like little wires connected to a bright red emergency button on the wall of a school hallway. When you touch something very hot like a boiling kettle, your body sends a message straight to your spine instead of waiting for your brain to think about it. Your spine is like the school caretaker who hits the alarm button immediately because there is no time to ask the headteacher for permission.
Once that alarm goes off, your muscles pull your hand away faster than you can say ouch. This is just like a fire alarm that rings loudly to clear the whole building the second it smells smoke. It does not wait for an adult to smell the toast burning or to check if the kitchen is tidy. It just makes a huge noise and gets everyone moving towards the door to keep them safe from any danger.
Your brain only finds out about the hot kettle after your hand has already jumped back to safety. It is a bit like arriving at the scene once the fire engines are already there and the students are standing on the playground. You wonder why everyone is outside in their coats, even though the caretaker did exactly the right thing to stop you from getting hurt.
Where the analogy breaks downA fire alarm cannot reset itself without a special key, but your nerves are ready to work again almost instantly.