system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't you be paralyzed from only the waist up?
gpt
The nerves go down from your brain.  Everything below the break in the nerve stops responding to input from the brain because it can't communicate with the brain anymore.  

If things *above* the break have stopped working, that means your brain has stopped working, which means you're dead.  This does happen sometimes, such as if the break is right below your brain (e.g. a properly performed hanging that snaps the neck).