Adrenalin
From Drug Rehab Wiki
Adrenalin is a hormone secreted by the human body whenever the person is afraid, excited, fearful or otherwise under stress. It stimulates the central nervous system, making the heart beat faster, increasing energy and sugar levels, and the ability to move. It is associated with the "fight or flight" response, in that whenever a person is aroused in fear, he will either confront the threat or flee from it. In either case, he will receive an "adrenaline rush" from his body.
Adrenalin is secreted from the two adrenal glands, which are located on top of each kidney.
Some people actually seek out "adrenalin rushes" by exercising, living their lives on a crisis level, and engaging in risky behaviors such as extreme sports or high stakes gambling. Playing video games can produce an adrenalin rush, and some scientists believe that is at the basis of gaming addictions. People who suffer from panic attacks or anxiety can have abnormally high levels of adrenalin.
Adrenalin can be used as a drug to treat asthma.