Adrenaline. Computer model of part of the molecular structure of the hormone adrenaline, or epinephrine (formula C9.H13.N.O3). The atoms (coloured spheres) are shown, linked together by chemical bonds. Adrenaline is a hormone produced in the adrenal glands above the kidneys. It is released at times of stress or fear to allow the body to work harder for a short time, leading to a fight or flight response. It increases the speed and force of the heartbeat, widens the airways to allow the lungs to take in more oxygen, and directs blood to the muscles to allow them to work harder. It is used as a drug to treat severe asthma and anaphylactic shock.