Which hormone is primarily responsible for the fight-or-flight response?

The hormone primarily responsible for the fight-or-flight response is adrenaline, also known as epinephrine. This hormone is produced by the adrenal glands and is released into the bloodstream in response to stress or a perceived danger. When adrenaline is released, it prepares the body to react quickly by increasing heart rate, elevating blood pressure, and enhancing energy availability. This physiological response equips an individual to either confront or escape a threat effectively.

Adrenaline's rapid effects are critical during emergencies, as they help to direct blood flow to essential muscles and brain areas while also facilitating quick decision-making. This hormonal surge also includes the release of glucose from energy stores, further supporting immediate physical activity.

In contrast, insulin primarily regulates blood sugar levels and is not involved in emergency response mechanisms. Cortisol, while also a stress hormone, plays a longer-term role in the body’s stress response and is involved in metabolism and immune response rather than the immediate reaction triggered by adrenaline. Serotonin is mainly known for its role in mood regulation and has different functions unrelated to the acute physiological changes associated with the fight-or-flight response.