Epinephrine, commonly known as adrenaline, is a hormone and neurotransmitter produced by the adrenal glands. It plays a critical role in the body's fight-or-flight response, increasing heart rate, blood flow to muscles, and energy availability. Epinephrine is also used medically in emergencies, such as treating severe allergic reactions (anaphylaxis) and cardiac arrest. The synthetic form of epinephrine is often administered via auto-injectors for quick delivery in emergencies.