system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does a strong punch to the jaw or face knock people out?

I've seen videos of people being knocked out by what looks like just a fist against the lower jaw. How does that knock them into being unconscious?
gpt
The exact mechanism isn't fully understood, and there's different kinds of knockouts, but knockouts are strongly associated with rotation of the head, probably putting pressure on the brainstem.  A hook to the jaw twists the head sharply which jostles the brain around and puts strain on the brainstem and spinal cord.  It's also gonna fuck with your balance having your head yanked around like that, which is why sometimes they don't lose consciousness as much as they just forget which direction is up and flop over.

The short of it though is twisting the spinal cord and brainstem.  That's why you usually hear about "mean left hooks" and stuff, because it's a lateral strike that jerks the head.