ACE Personal Trainer Practice Exam 2026 - Free Personal Trainer Practice Questions and Study Guide

The sympathetic nervous system is responsible for the body's fight or flight response. When faced with a perceived threat or stressful situation, this system triggers physiological changes that prepare the body to either confront the danger or flee from it. These changes include an increase in heart rate, dilated airways to improve oxygen intake, enhanced blood flow to muscles, and the release of adrenaline, all of which enhance an individual's ability to respond quickly and effectively to the threat.

In contrast, the parasympathetic nervous system operates to promote the rest-and-digest response, calming the body after a stress response. The central nervous system, which includes the brain and spinal cord, processes and interprets sensory information but is not directly responsible for the fight or flight response itself. Lastly, the somatic nervous system controls voluntary movements of skeletal muscles, rather than involuntary stress responses, further distinguishing it from the sympathetic nervous system’s role in acute stress reactions.