Why do animals kick around after they get their heads cut off and humans don't?

I saw a clip of a cow getting decapitated with a very sharp blade. It was very fast and the cow's body fell over and kicked for a good 20 seconds. I saw a pig get it's head cut off with a chainsaw, it's body went into running mode for 30 seconds. I've seen videos of humans getting decapitated and their body doesn't move. Why is this?