Now as we begin to run, we have to see where we're going. And so that means our pupils increase, they dilate so that more light gets into our eye and we can better see where we're actually running to. So we see that our sympathetic nervous system this is the division of the autonomic nervous system that is responsible for the fight or flight response. This includes dilating our pupils, increasing the heart as well as our breathing rate and increasing the mouth that we sweat. So that's because when we sweat we're basically expelling the byproduct our energy. So as we produce more ATP in our muscles, that creates more energy, more thermal energy as a byproduct.