Psychologists sometimes call the drenal glands the emergency centers of the body. As you can see above they sit just above the kidneys and produce adrenaline and cortisol. As you've probably experienced, adrenaline boosts energy production while still trying to conserve as much energy as possible while your muscles are busy smacking your friend for scaring you. Adrenaline actually does more than you would think.
-contraction of our heart muscle and constriction of our blood vessel to provide more blood to the body
-opening the tiny airways to the lungs to allow inhalation of more air
-breakdown of fat into glucose to energize our muscles
-opens the pupils (dilates) of our eyes to enable better sight during emergencies!
All of this together allows people to perform amazing acts of heroism in crisis situations (but are still constrained by physical limitations obviously). One mother was filled with adrenaline when her child was trapped under a heavy car, enough even to lift the end of the car some say up to four inches off the ground!
This shows how impressive the human body is and how it deals with intense situations.