I think the shock to the nervous system has been dismissed as a stopping mechanism. There have been too many accounts of people getting shot in a gunfight with .357 mags and .45 ACPs that didn't know they had been shot. All they said they felt was stings. To reiterate an account I gave earlier, I saw an actual police video of a thin woman that was shot 3 times in the torso and she didn't go down, and ran around a car with three .45 ACP shots in her torso. Such accounts are not uncommon.
There are numerous accounts of LEO getting shot but they still subdue the BG. There are numerous accounts of BGs receiving fatal gunshot wounds and fighting for minutes.
In another police video, a BG shot an officer in the arm with a .25 cal. The officer died at the scene.