Which item is a trigger for PNS backlash?

• A. The threat perception has diminished
• B. The perception of injury
• C. Trauma to a vital system
• D. Exhaustion of aerobic and anaerobic systems

Answer: (B)

The key idea is how the autonomic nervous system responds to threat cues and then settles down. When someone perceives injury, the brain registers potential damage and the body kicks into protective mode: heightened alertness, faster breathing, and other arousal signs. After this initial surge, the parasympathetic system steps in to calm things, promote recovery, and restore balance—this rebound toward rest-and-digest is what’s meant by a PNS backlash. So the perception of injury is the cue that triggers that parasympathetic rebalancing. The other scenarios don’t specifically drive this parasympathetic rebound: diminished threat perception lowers arousal, trauma to a vital system represents severe damage rather than a reflexive calming response, and fatigue is about energy depletion rather than a cue for parasympathetic resetting.