With VNS analysis, the functional state of the autonomic nervous system (ANS) is measured. The ANS is the central control and regulatory system in our body, responsible for governing all the involuntary organ systems such as heart rate, respiratory system, digestive system, hormonal system, immune system, blood pressure, and more.
The ANS consists of the sympathetic nervous system (fight-or-flight response) and the parasympathetic nervous system (rest and digest response).
Originally, the ANS evolved to prepare the body for fight or flight responses. In a metaphorical sense, when a saber-toothed tiger approached early humans, the sympathetic nervous system was activated. It increased blood pressure, tensed muscles, and released sugar into the bloodstream. The body entered a state of extreme tension and heightened focus.
At the same time, the parasympathetic nervous system was suppressed along with all the systems not required for fight or flight, such as the immune system, hormonal system, and digestive system. It wouldn't be appropriate to feel the need to use the restroom in a life-threatening situation.
After physical activity (fight or flight), the body could recover and regenerate as the parasympathetic system was reactivated, and the sympathetic system was toned down. Cells could regenerate, and the body could replenish its strength. It was truly a brilliant mechanism of nature.
However, in modern times, the problem is that the body is exposed to similar stress factors as it was with the saber-toothed tiger, but physical activity is lacking. Standing in the supermarket with a malfunctioning debit card, having an urgent appointment, the children refusing to go to kindergarten, being late for work, dealing with a demanding boss, and so on.
The issue here is that the ANS prepares the body for fight or flight in these stress situations, just like it did with the saber-toothed tiger. However, it's difficult nowadays to dissipate this stress through physical activity. You don't necessarily want to step into the boxing ring with your boss or start a sprint in the supermarket.
If stress situations persist over a prolonged period, eventually, the ANS becomes unable to establish a balance between rest and recovery (parasympathetic) and fight or flight (sympathetic). The fight-or-flight response solidifies into a state of chronic stress (constant activation of the sympathetic system). This chronic stress raises blood pressure and increases blood sugar levels (which aren't consumed through muscle movement). The sympathetic system keeps all organs in a state of tension, even high tension. On the other hand, the parasympathetic system operates at a low level, affecting the digestive system, hormonal system, and immune system.
Eventually, at any time of the day, the ANS can no longer replenish the energy stores or switch cell communication from fight or flight to relaxation, regeneration, and recovery.
In such a situation, it's only a matter of time before all emergency resources in the body are depleted, and the ANS dysfunction manifests as organic disease symptoms, becoming chronic.