Each digit has two nerves, one on either side,” Dr. Botek says. “So no matter where you hit your toe or how you stub it, it’s going to affect a nerve impulse from your toe to your brain.” This nerve impulse is modulated by sensory neurons called nociceptors, which fire off information to the brain whenever they sense an external stimulus that may cause harm to the body. That includes extreme heat or cold, certain chemicals that could burn the skin, or mechanical pressure that could damage the tissue (like the force involved when you bang a toe into the hard foot of a chair, for instance). “When that specialized neuron gets activated, it fires, sending that information to the spinal cord,” Jeffrey Mogil, Ph.D., a neuroscientist and professor of pain studies at McGill University, tells SELF. From there, the information is processed by the brain and, eventually, you perceive it as pain.
You haven't changed (you are made up of the same atoms), but the force exerted on you is different. Physicists like to say that your mass hasn't changed, only your weight.
