Autonomic Overdrive


How Stress Affects our Nervous System

Stress Response in the Autonomic Nervous System


Stress is extremely detrimental to our health.  It affects us in the background and sometime we don’t even realize it until enough stress builds up to grab our attention.  To understand how stress can affect us long term, without really thinking about it, we need to look at the Automatic response of the human nervous system.

Ever wonder what part of your nervous system takes care of all the bodily processes that you don’t have to consciously think about? Breathing in and out is probably its most famous action but everything from digestion, hormonal production, body temperature, immediate survival, and stress is regulated by the Autonomic Nervous System, which is a subdivision of the peripheral nervous system.

The Peripheral Nervous System is everything in your nervous system, excluding the brain and spinal cord. These are the nerves that run through your gut and to all your extremities.

The autonomic nervous system has two separate and completely opposite divisions that counterbalance each other, they are the sympathetic; fight or flight, and the parasympathetic; the rest and digest divisions. There is an eternal battle going on between these two subdivisions and you are constantly being pulled in each direction like a tug of war rope. Since you don’t fully control this portion of the nervous system yourself, even small amounts of stress can tug the rope and pull your system into high alert mode. This can cause problems with your physical and emotional health because you could be in stressful overdrive when you should be resting and regenerating, and since we don’t consciously control it it is easy to miss.. Remember that your recovery needs to be equal or greater towards your work load or you will start wearing down.

ParaSympathetic Division
aka: Rest & Digest

This division of the ANS (Autonomic Nervous System) is activated and in full swing when your environment is calm and peaceful and there is little to none outside stress in your environment.  This parasympathetic division helps us out long term and plans for the future. Your body knows that after a long day at the office, arguing with your boss, and a hour in traffic, your fuel sources are low and your stress hormones are high. To combat this and prepare for the next day your body needs to recover so the parasympathetic side of the ANS takes over. The reason we have this side of the ANS is so your body can replace energy stores, regenerate tissues, and eliminate wastes.

This guy is in Parasympathetic Mode.

You can see why they call it the “Rest and Digest” division because it really takes control during your recovery and repair. Your body has a hard time starting these regenerative processes when you’re stressed out or in an uncomfortable environment because these things cause the other side of the ANS, the sympathetic flight or fight, to be activated.

Sympathetic Division
aka: Fight, Flight, and Freeze

This division is all about short term survival.  You need to remember that Humans have been around for awhile and a lot of these stress mechanisms were around during the hunter and gathering stage in human evolution. They kept us alive then and they do a pretty good job of keeping us alive now. The easiest and most well known description of the sympthatic response is: What would happen if you are being chased by a tiger?

If you were in Asia and there was a hungry tiger behind you, without a cage, your body would make a few sudden physiological changes in response to seeing it. 


  1. Your heart rate would increase so you can supply your muscles with more oxygen, making them more efficient and your heart would start to contract more forcefully increasing circulation. Better for you to run faster and longer!
  2. Your pupils would dilate, allowing more light to enter the eye, so you can see more of your surrounding and the current situation giving you the best chance at survival. No tripping on roots or rocks!
  3. The blood vessels in your digestive system would vasoconstrict so more bloodflow can be used for your muscles for movement. They can help you get away from the threat. Your body knows there is no point in digesting food if you wont make it another few hours.

This is just an example and the tiger can be substituted with other stressful things, like time management, debt, family, and love.  The sympathetic response will override the “rest and digest” division during physical altercations and emotional stress. Your body does not have time to repair and digest when you’re running from a tiger. So most of your physiological survival fight or flight mechanisms take over.  In your body’s opinion the only thing that is important is to get away from the threat and you can regenerate and recover later when the threat is gone and you are safe. The problems occur when your body is in this fight or flight mode, even when you think you are resting and relaxing.  Have you ever had a full nights sleep and woke up not feeling too refreshed? This could be caused by an overload of stress!

Freeze Response: There has been another discovery in the sympathetic division of the ANS.  The freeze response is exactly what it sounds like.  Some creatures will freeze and lie still in response to a perceived threat.  This has shown to be an effective mechanism for survival because not everything is trying to eat you, they are just scared of you so as long as you aren’t moving, the freeze greatly increases your short term survival.

How can these autonomic responses affect us?


 So now we know the different directions that our autonomic nervous system’s autopilot can steer us we can take a look how that can be ill to our health.  

Humans are busy and we have other things to think about and that is why a lot of these process are done automatically.  Just like anyone our body can be prone to errors and mistakes.  Think about your last major road rage incident (this is Austin traffic we are talking about). It does not matter who was at fault but can you remember how worked up your body got? You probably experienced anger and frustration, along with an increased heart rate and breathing.  You also may be flexing your muscles which increases muscle tone. This is a sympathetic response and since most all of us have experienced this at some point, you can’t just turn it off.  It can last an hour or a week and it can even resurface when you think about it days later. Combine the road rage incident with a stressful day at work while fighting with your significant other, your body is in complete survival mode.  It perceives multiple threats in the course of the day so you are on high alert leaving no time for rest and regeneration.. Once this negative stress response takes over during normal day to day things you start missing out on a lot of recovery processes in the body.  Road rage is just one common example but if stressful situations are a common occurrence for you then long term it can suppress the immune system and lead to chronic conditions. When you’re in sympathetic overdrive it can keep you from sleeping at night.  Your mind wants you to sleep but your body is weary of predators that can be lurking so it annoyingly keeps you awake, just in case.

How can we keep this automatic response in check?

The good thing is you can fight back against this negative stress response. The most important thing is awareness.  You need to recognize when a sympathetic response may be forming and understanding the different types of stress.  Things to look for are increased heart rate, increased breathing rate, pupil dilation, irritation and perspiration. Once you recognize the signs then ask yourself if you really are perceiving a threat or maybe you are making a mountain of a molehill. Things usually are not as bad as they seem and its important to realize that life in general is pretty tough so its best to tackle stressful situations as soon possible and with your head held high. Every time you complete something that is hard and stressful you will be able to surpass that next time and the hardest things get easier, allowing you to tackle even harder obstacles.

Other things that can help with sympathetic dominance and help push you into rest and digest mode are(in no particular order):

  • Breathing exercises
  • Meditation
  • Massage Therapy
  • Yoga
  • Tai Chi
  • Mindfulness
  • Chiropractic
  • Well Balanced and non processed Diet

Nick Picchetti L.M.T.