Overview
Hyperarousal refers to a physical state that the body enters as a response from the nervous system to continuous stress. This includes hypervigilance, and it contrasts withhypoarousal.
In a typical stress response, the amygdala sends signals to the adrenal glands to flood the bloodstream with adrenaline and norepinephrine and trigger a potential fight-or-flight response while increasing your heart rate, constricting muscles, dilating pupiles, and making breathing more shallow. It also releases the stress hormone cortisol to flood your blood with glucose for energy, sharpen your focus on stimuli around you, and slow down processes like digestion and reproduction that aren’t needed in an emergency. The prefrontal cortex simultaneously processes the actual information that triggered the amygdala and can mute the stress response if there’s no real threat, like realizing that the loud sound you just heard was a car backfiring and not a gunshot. The brain has dedicated receptors to monitor the amount of cortisol in the blood and stop producing it past a certain point, with the premise that the threat has likely been dealt with.
In hyperarousal, the amygdala is constantly firing signals to produce stress hormones, and the brain’s receptors become desensitized to the levels of cortisol in the blood. This is literally toxic; the hippocampus region of the brain atrophies in response to cortisol which makes it harder to add context to the memory of threats. Instead of being able to process a subsided threat as something in the past, the threat appears continually present to the brain, so the amygdala keeps firing. The loop is incredibly damaging to the brain, which is why chronic stress is such a big deal and takes more than a shift in mindset.