The adrenaline glands, located on top of both kidneys, are glands that produce hormones to regulate blood pressure, bodily functions, metabolisms, etc. Adrenaline is released whenever the blood is redirected towards the muscles, causing surges of energy. In general, adrenaline increases blood flow in your body, which causes the heartbeat to increase, or give the feeling of a racing heart. Between the football players and the heartbeat rate, they are getting rushes of adrenaline from either participating in the game or cheering on their team from the sidelines. Hope that made sense.
The very highest level; this is because of the 10% rule in which 10% of the energy in a trophic level directly below one level is present in that level.
