system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does your sleeping body ignore certain pains?

If you were being punched in the face or somebody tried to drown you whole you were sleeping your body would wake up. 

On the flip side, your body ignores your limbs falling asleep or body parts parts feeling sore to the point ligaments could be tearing? Like I've woken up after sleeping and my wrist hurt for days after bad sleep but my brain was too dumb to wake my body and have me turn over.
gpt
Generally speaking when you're asleep you tend to react to sudden changes, but not so much to gradual ones. If someone stuck you with a pin, you'd wake right up, but if someone spent an hour gradually pinched you harder and harder... maybe not. 

It's the same with sounds... you can fall asleep (eventually) to a racket, but if that *changes*... even goes away suddenly... you might wake up. It makes sense if you think about it from an evolutionary perspective; you need sleep, especially if you're hurt. By the same token, if someone in yourself or your environment suddenly, radically changes, you need to be *awake* right away.