Which hormone plays a crucial role in the fight-or-flight response?

Epinephrine, also known as adrenaline, is the hormone that plays a crucial role in the fight-or-flight response. When an individual perceives a threat, the adrenal glands release epinephrine into the bloodstream. This hormone triggers a series of physiological changes that prepare the body to either confront or flee from the danger.

These changes include an increase in heart rate, heightened blood flow to muscles, and enhanced energy production through the release of glucose from energy stores. This rapid response allows the body to react quickly to stressful situations, making it vital for survival.

The other hormones listed—cortisol, insulin, and thyroxine—do not directly contribute to the immediate fight-or-flight response. Cortisol is involved in long-term stress responses and helps regulate metabolism and immune responses. Insulin is primarily responsible for glucose uptake and regulation following meals. Thyroxine plays a role in metabolism and development but is not involved in acute stress responses. Thus, epinephrine's specific function in heightening immediate physiological readiness underscores its critical role in managing acute stress through the fight-or-flight response.