An adrenaline junkie is somebody who engages in sensation-seeking behavior through “the pursuit of novel and intense experiences without regard for physical risk”. Such activities include extreme and risky sports,. The term relates to the increase in circulating levels of adrenaline during physiological stress. Such an increase in the circulating concentration of adrenaline is secondary to activation of the sympathetic nerves innervating the adrenal medulla, as it is rapid and not present in animals where the adrenal gland has been removed. Although such stress triggers adrenaline release, it also activates many other responses within the central nervous system reward system which drives behavioral responses, so while the circulating adrenaline concentration is present, it may not drive behavior.