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Posted 11/04/2010

In my previous blog I discussed the two parts of the autonomic nervous system: the sympathetic and parasympathetic systems.  As a way to understand how the sympathetic and parasympathetic nervous systems function in harmony, think of the analogy of a car’s cruise control.  The function of a car (the human body) is to get you where you need to go.  The sympathetic system is the accelerator and the parasympathetic system is the brake.  You must have both in order to safely get to where you need to go.  The accelerator excites the engine by burning gas, while the brake slows down and conserves burning of gas.  You cannot get to your destination with only an accelerator, and you can’t stop your car without a brake.  Using this analogy, you can see it would be more than a bit problematic if one or the other was not working.

A driver sets the cruise control mechanism by pushing a button when the car has accelerated to some desired driving speed.  The control mechanism then takes over and begins to constantly compare the car’s current speed with the desired driving speed.  If the car slows down while going up a hill, the cruise mechanism automatically depresses the accelerator (sympathetic nervous system) and thus brings the car back up to the desired driving speed.  Similarly, if the car begins to exceed the desired driving speed while going down hill, the mechanism releases the accelerator to slow down the car.  Whenever the car is at the desired speed, the mechanism makes no changes.  The accelerator and brake will work in opposition, in the sense that any perceived error, such as a drop in speed, produces action by the system to counteract the error by changing the output of the engine.

In order to maintain health, you have to apply the brake pedal regularly in order to bring the speed of your car down and you may at times need to apply the accelerator to bring the speed of your car up.  Obviously, the actions involved in performing the function of cruise control are far more complicated for the human version versus the car version, yet they are very similar. 

Overuse of the accelerator (sympathetic nervous system) as seen in the states of anger, anxiety and hostility sets off the parasympathetic nervous system (brake), reflecting the autonomic nervous systems attempt to achieve balance.  In a simple yet reasonable analogy, the driver must somehow maintain his purpose of keeping the car traveling at a given “balanced speed”, but be prepared at any given time to abandon that purpose if any problem should arise. 

In my next blog I will discuss several different ways in which one’s autonomic nervous system may be malfunctioning, and the various symptoms that might become apparent.  Please stay “tuned”!!!

Posted November 4, 2010 at 10:38am by Jason Masek.
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