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

Norepinephrine is the hormone primarily responsible for the fight or flight response. When confronted with a stressful situation, the body triggers a rapid response to prepare for either confrontation or escape. Norepinephrine, released from the adrenal medulla, acts quickly to enhance heart rate, increase blood flow to muscles, and heighten alertness. This immediate response is crucial for survival, as it readies the body for quick physical action.

Other hormones play different roles in stress and metabolism but do not directly trigger the immediate physiological changes associated with the fight or flight response. Cortisol, for example, is a glucocorticoid hormone that helps regulate metabolism and manage long-term stress responses, acting more gradually rather than causing the immediate effects seen with norepinephrine. Insulin is primarily involved in glucose metabolism and lowering blood sugar levels, which does not relate to stress responses. Progesterone is mainly associated with reproductive processes and does not have a role in the acute stress response. Understanding the specific functions of these hormones helps clarify why norepinephrine is key in initiating the body's rapid response to stress.