I don't see how you intended to use those examples because they obviously don't apply to human beings. Also, in combat sports, a blunt impact on the head from the opponent's fist does turn you off instantly on a regular basis. It doesn't kill you but the fight or flight system doesn't apply there even in the heat of battle. People are instantly incapacitated by such methods regularly.
They do apply. While humans do have higher functions (obviously) that are controlled by our more evolved brain, we still have "animal brains" at the base. Read other post for some more on that.
I'm glad you brought up blunt impact and knock outs. Very specific nerves must be hit (most notably the one in your chin, on both sides, if you feel it there is a little notch. Punch someone there and you can easily put someone out). However, the key here is the blunt damage and how energy is dispersed.
An arrow cuts through and is slowed down by the matter/tissue that it impacts. A fist say, or a billy club is much more likely to put someone down thanks to the reverberations of blunt force trauma. I'd rather be stabbed in the gut than have someone swing at my stomach full force with a baseball bat for isntance. The stab will make me bleed, true (I have lots of blood I can lose before it even becomes dangerous. Usually around 2 pints). Chance are though, he isn't going to damage anything I can't live without. That baseball bat though, it's going to damage nearly every organ (kidney, liver, etc). This is much more dangerous as not only are these organs essential, but the internal bleeding is obviously much harder to stop.
Anyway, that's getting way off subject and rambling a bit.
Point is blunt force trauma is far more likely to "knock out" than something like an arrow that is slicing through tissue and not dispersing much energy beyond the points it actually hits.