Now as we begin to run, what begins to happen is more blood begins to pump to our skeletal muscles so that we can run away. And as more blood is being pumped to our muscle, those muscles are basically using more energy creating more ATP molecules and they need more oxygen. And so the rate of our respiration increases as well as the rate of our heart. 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.