Please help! Is there something physiological in running?

I was running with my dog a few days ago, and just felt like I [i]had[i] to keep going. Some part of my brain knew I needed to stop, but I couldn't....I was feeling a little insane, huffing out "stop" but doing nothing about it, and even going faster. By the time I finally did stop my pulse was REALLY high (so much so the right side of my neck REALLY hurt, and the inside of my ears hurt from the pressure). It's not the first time I've run myself to exhaustion, but it had the scariest aftermath. So why did I not stop running sooner? Is it the same case when you're eating and feel yourself getting full, but still want to eat more...only with adrenaline in place of food?