NCLEX HIV/AIDS Practice Test 2026 - Free HIV/AIDS Practice Questions and Study Guide

The fight-or-flight response in the alarm phase of general adaptation syndrome is mediated by the sympathetic nervous system. When activated, it triggers rapid physiological changes such as increased heart rate and blood pressure, bronchodilation, pupil dilation, and redirection of blood flow to muscles, preparing the body for quick action. The parasympathetic system promotes rest and digestion and would dampen these effects, so it is not the mediator. The enteric nervous system governs gastrointestinal function and operates independently of this systemic arousal. The central nervous system coordinates responses, but the immediate mediator of fight-or-flight is the sympathetic branch of the autonomic nervous system. (For context, longer stress involves the HPA axis and cortisol release, but the instantaneous fight-or-flight effect is SNS-mediated.)