The drugs are normally prescribed to treat attention deficit hyperactivity disorder (ADHD), but healthy students use them to get a leg up in school, by improving focus, concentration and memory.
Adrenaline, or epinephrine, is a hormone that dilates an individual's air passages and increases his heart rate when he is faced with a stressful situation. The hormone is secreted from the adrenal glands to help ensure survival under dangerous situations.
Adrenaline on its own can be triggered in many ways. For instance it can be a result of shock, or of a confrontation, and this then causes an increased heart beat, shaking, and racing thoughts. The solution is to try and control your breathing and to remove yourself from the stressful situation.