Which part of the nervous system is responsible for the 'fight or flight' response, leading to an increased heart rate?

The sympathetic nervous system is responsible for the 'fight or flight' response, a physiological reaction that occurs in response to a perceived threat. This system activates the body's stress response, preparing it for action by increasing heart rate, elevating blood pressure, and redirecting blood flow to muscles. These changes help enhance physical performance and readiness for either fighting the threat or fleeing from it.

In this context, the sympathetic nervous system’s activation is driven by the release of stress hormones, such as adrenaline, which hastens various bodily functions to improve survival odds during emergencies. In contrast, the other systems mentioned serve different roles: the parasympathetic nervous system promotes rest and recovery; the central nervous system processes sensory information and coordinates activity; and the somatic nervous system controls voluntary movements of skeletal muscles.