Hypervigilance is a hyperarousal symptom, seen in post traumatic stress disorder (PTSD). Hypervigilance is the constant scanning of your environment for any signs of danger, and you have increased alertness and are jumpy and easily startled. Hypervigilance and hyperarousal are triggered by the activation of the fight or flight response:
When the fight or flight response is activated from a traumatic event or reminders of the traumatic event, the amygdala activates the locus coeruleus, which then activates the sympathetic nervous system. The activated sympathetic nervous system when interacts with the cardiovascular system, with resultant increase in heart rate and blood pressure, as the sympathetic nervous system directly activates the heart and constricts blood vessels.
When the sympathetic nervous system is activated long term from hypervigilance and hyperarousal, then it can lead to increased risk of high blood pressure (hypertension), clogged arteries (atherosclerosis), heart attacks (cardiac ischemia and myocardial infaction), and sudden death.
So when you have PTSD, the anxiety can be triggered internally from traumatic memories stored in the hippocampus. The memories stored in the hippocampus can activate the amygdala, as the hippocampus is connected to the amygdala, and the sympathetic nervous system is activated with these traumatic memories. This then maintains the hypervigilance and hyperarousal.
Because of these long term risks from hypervigilance, it is important to seek treatment to eradicate it. The following video explains how hypervigilance and PTSD develop, and what you can do to treat it: