Which system is primarily responsible for fight or flight responses?

The sympathetic nervous system is primarily responsible for regulating the fight or flight response. This system activates the body's physiological reactions in response to stress or perceived threats. When faced with danger, the sympathetic nervous system stimulates various bodily functions, such as increasing heart rate, dilating pupils, and redirecting blood flow to muscles, which prepares the individual to either confront the threat or flee from it.

In contrast, the parasympathetic nervous system promotes a state of calm and is involved in restorative processes following the fight or flight response. While the central nervous system (which includes the brain and spinal cord) integrates information and sends signals throughout the body, it does not specifically govern the fight or flight response. The endocrine system plays a role in this response by releasing hormones like adrenaline, but it is the sympathetic nervous system that initiates these immediate actions and prepares the body for rapid response. Therefore, understanding the distinct roles of these systems clarifies why the sympathetic nervous system is the correct choice for this question.