Adrenaline, also known as epinephrine, is a hormone produced by the adrenal glands and a small number of neurons in the medulla oblongata in the brain. It is involved in regulating visceral functions, such as respiration, and is a key component of the bodys "fight or flight" response. When a person is faced with a stressful or dangerous situation, their brain sends messages to the adrenal glands to start releasing adrenaline into the blood. Adrenaline triggers the bodys fight-or-flight response, causing air passages to dilate to provide the muscles with the oxygen they need to either fight danger or flee. It also triggers the blood vessels to contract to redirect blood toward major muscle groups, including the heart and lungs. Adrenaline causes a noticeable increase in strength and performance, as well as heightened awareness, in stressful times. The effects of adrenaline can last for up to an hour after the stress has subsided.

Adrenaline is also used as a medication to treat many life-threatening conditions, such as severe allergic reactions (anaphylaxis), cardiac arrest, croup, and asthma when other treatments are not effective. When a person has a lot of adrenaline in their blood, they don’t feel as much pain, so they can keep running or fighting, even if they are injured. However, the body can also release adrenaline when it is under stress but not facing real danger, which can create feelings of dizziness, light-headedness, and vision changes. Medical conditions that cause an overproduction of adrenaline can lead to health problems.