Conscious decision-making and upper motor neurons can override the stretch reflex and pain perception.

“You could override that stretch reflex by way of a decision made with your upper motor neurons, your insula, and your cognition, and almost certainly those von Economo neurons, which would be screaming, "Don't do this, don't do this, don't do this," could shuttle that information to brain areas that would allow you to override the reflex and essentially push through the pain. And maybe even, in fact, even not experience the pain to the same degree or even at all.”