Sympathetic & Parasympathetic

Both part of the autonomic nervous system, the sympathetic and parasympathetic nervous systems work involuntarily. Sympathetic is responsible for the response commonly referred to as “fight or flight,” while parasympathetic is referred to as “rest and digest.” Both originate in the spinal cord and branch out from there.

The sympathetic nervous system is the part of the autonomic nervous system that prepares the body to react to stresses such as threat or injury. It causes muscles to contract and heart rate to increase.

The parasympathetic nervous system is the part of the autonomic nervous system that controls functions of the body at rest. It helps maintain homeostasis in the body. It causes muscles to relax and heart rate to decrease.

Significance of X axis

Imagine driving a Porsche. All the power and handling you could want but extremely vulnerable and dangerous to drive if the brakes are poor. The same applies here. If the Parasympathetic (PS) Braking is impaired from overuse combined with excessive Sympathetic (S)-Lifestyle choices, then the plot will shift and stay shifted to the LHS (Left Hand Side). Unhealthy lifestyle choices fatigue the braking response and feed into the overt Sympathetic situation.

A shift to the RHS (Right hand Side) suggests an inability for the body to rise up to the task in the case of external stress. Just as in the case of a Porsche, the brakes are working well but the system is unable to accelerate when the need arises hence operating below capacity.

Adjustments and certain lifestyle modifications shift the balance back towards a healthier centerline plot.

Significance of  Y axis

The vertical plot is associated with Autonomic Activity. Simply put, this represents the amount of reserve and resiliency that the individual is working with. We define this reserve as their amount of “Coping Capacity”. Imagine that a combination of lifestyle stressors and events constantly “pushes” down on us while our inborn, internal capacities resist this pressure. Now imagine that this “Equation of Life” is being played out under the guidance of the central nervous system. If the external forces gradually overwhelm the internal resistance and interfere with the nervous system, the coping capacity is reduced.

Increasing the coping capacity is desirable. The healthy and well people find their plots within the green box on the PWP (Pulse wave profiler)  graph. This allows for a bit of imbalance but the reserve must be high; within the 80-100 range. Above 100 is desirable and this is commonly found among athletes.  Having an autonomic activity score lower than 80 puts the individual in a vulnerable position. They do not have the necessary reserves to remain resilient in the face of ongoing or upcoming stressors. They have a suppressed recovery response and as the stresses accumulate or continue their health status can decline more rapidly. The statement of “getting sicker, quicker” applies here.

The likely causes for people falling outside the normal range are:

  • Physical stress e.g.
    • birth traumas
    • falls
    • car accidents
    • poor posture
    • driving long hours etc
  • Emotional stress
    • relationships
    • career
    • children
    • hold-in feelings
    • fast paced life etc
  • Environmental stress
    • Environmental e.g pollution
    • Smoker or second hand smoke
    • Poor diet
    • High caffeine amounts
    • Excessive sugar
    • Artificial sweeteners etc






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