Thus the purpose of this blog post is to delve a little deeper than the catchy ‘sayings’ and highlight what the autonomic nervous system (ANS) and its subsequent parasympathetic (Rest & Digest) and sympathetic (Fight or Flight) divisions relate to and the role they play in homeostatic balance. Furthermore, to gain a basic understanding of HOW? and WHY? these fundamental mechanisms operate, which in turn will grant us the ability to grasp why the emotions and the activities we do can affect the subsequent balance of the autonomic nervous system which is so integral to our overall health and wellbeing. Furthermore, we will briefly mention how a regulatory form of therapy such as acupuncture is able to balance and promote the parasympathetic “healing” state and thus ameliorate a range of associated health conditions.
Firstly, it is important to introduce the autonomic nervous system (ANS) starting with the hypothalamus (a structure in our brain) which acts as the highest control centre of the autonomic motor neurons that innervate our visceral organs. Thus the hypothalamus as the “centre of homeostasis” is continuously (unconsciously/automatically) adjusting the activity of the visceral organs to match the individual’s activity and energy requirements. In this context, how the hypothalamus relays these impulses/commands that initiate the associated visceral (organ) actions is via the autonomic motor neurons (parasympathetic motor neurons & the sympathetic motor neurons). It is important to note that the above mentioned autonomic motor neurons constitute the two divisions of the autonomic nervous system, these divisions being the parasympathetic which is associated with the commonly known “rest and digest” “relaxation” “healing/repair” state, and the sympathetic which is responsible for the “fight or flight” “stress” response.
So, we can see from above a few key points we need to keep in mind, that the ANS innervates our internal organs and their associated functions with the main goal of mobilizing the required amount of energy needed. The ANS, as the name suggests, is “automatic” thus we do not have direct conscious control over it as we do over somatic motor neurons that innervate skeletal muscle. It is the hypothalamus that acts as the control tower that adjusts our internal organ activity and thus homeostasis. Now, you may be thinking if we have no direct control of the functioning of the ANS, how can meditation, acupuncture, or other activity affect the state of our ANS? This is due to numerous factors including the fact that our limbic system (centre of emotions) is wired into our hypothalamus. Thus, the emotions you have affect the hypothalamus (centre of homeostasis) and thus the associated parasympathetic/sympathetic motor neuron innervation of your internal organs. Furthermore the activity you do i.e. running, boxing, eating, meditating, studying … will either increase or decrease your energy requirements and thus engage the ANS accordingly to meet said requirements.
Before we go on I would like to highlight some basic anatomy that may assist in making things more clear. The parasympathetic motor neurons are situated in the cranial nerves and in the sacral nerve fibres. The sympathetic motor neurons are found in the thoracic and lumbar nerve fibres. Thus there is a clear anatomical difference and this is why the parasympathetic division of the ANS is also known as the craniosacral and the sympathetic as the thoracolumbar. Now, these respective neurons travel from the spinal cord/cranial nerves to the organs they innervate and with the exception of the adrenal medulla (of the adrenal gland), all the organs receive dual innervation by the sympathetic & parasympathetic motor neurons.
With this image in mind and keeping the main functional ‘goal’ of the autonomic nervous system in mind (which is to provide the necessary energy requirements to meet demand), we can understand how in states of “stress” or “Fight or Flight” the sympathetic neurons start to fire and thus your heart rate and myocardial contractility INCREASES. It does this to increase cardiac output and provide an increased amount of nutrients and oxygen to your bodily tissues to meet the increase in energy demand so you can RUN! Or FIGHT! Interestingly the sympathetic motor neurons that innervate the gastrointestinal tract fire as well and this DECREASES gut motility and digestive function. Reason being is that if you are in a “fight or flight” state you don’t want to waste precious energy on digesting lunch but rather utilise that energy for combat or fleeing. Other organs that are affected by the innervation of the sympathetic motor neurons include the liver and adipose tissue resulting in glycogenolysis & lipolysis which increase the circulating glucose and fatty acid levels for (ATP) Adenosine triphosphate production (energy). The lumen of the airways increases due to the bronchodilation that occurs to INCREASE oxygen availability for cellular respiration. DECREASE in mucous secretions occurs, INCREASE in blood pressure (due to increased cardiac output) occurs, INCREASE in sweating (due to increase cellular respiration & subsequent release of heat) & Decrease in salivation occurs. Basically in essence the sympathetic “stress” “fight or flight” response readies the body for combat or fleeing and not for heling and digesting. In essence it is a catabolic response that utilises great amounts of energy for that purpose.
Now if we look at the parasympathetic response being one of “resting & digesting” we can imagine that the opposite occurs. Anabolic, regenerating and healing processes take place which translates to increased blood flow to the gastrointestinal tract, relative decreased blood flow to the heart and skeletal muscle as they are not needed to ‘work’ so hard and thus increased systemic blood circulation, glycogenosis & lipogenesis (process of storing circulating glucose and fatty acids to glycogen and triglycerides respectively), INCREASED salivary and bronchial secretions & DECREASE in blood pressure. Thus the essence of the parasympathetic state is one of energy conservation, down regulation, the rest & digest state that is needed for growth, repair and healing.
So this is all good … Our state of balance ‘homeostasis’ is dependent on many things including the dual innervation of our parasympathetic and sympathetic aspects of our autonomic nervous system. If a LION is chasing you we need the sympathetic fight or flight neurons to ‘fire’ and the associated increase/decrease in organ functions that combine to mobilise energy so we can RUN. If we are sleeping we need parasympathetic innervation to enable us to heal, rest and repair. The REAL ISSUE is when due to our emotional state and/or lifestyle we maintain a sympathetic dominant state when there is no LION chasing us… For ALL the reasons/concepts discussed in the paragraphs above this ANS imbalance can manifest in the acupuncture clinic as individuals presenting with palpitations, and/or high blood pressure, anxiety/nervousness/phobias, poor digestion/assimilation, IBS signs and symptoms, constipation, asthma, abnormal sweating, thermoregulation issues & much more…
Perceived stress is just as real as a lion chasing us, and due to (as mentioned above) the limbic system directly feeding into our hypothalamus, the associated physiological responses can become the cause of pathology. Our thoughts, emotions and activities directly relate to our subsequent organ function and the above paragraphs highlight exactly that through a western physiological framework.
Now, acupuncture philosophy and practice has recognised since its inception some 2500 years ago the integral link between body, mind & environment, and I have highlighted this deep connection in previous blogs. I will say however that in the acupuncture clinic I find that nearly all individuals benefit, regardless of their main complaint, from acupuncture treatment strategies targeted at down regulating sympathetic innervation and promoting parasympathetic innervation. Granted that the acupuncture classical texts did not mention the autonomic nervous system with its parasympathetic and sympathetic divisions. However one just needs to read a classical acupuncture text to realise that the “human condition” was then as it is today, and although the ‘terminology’ used in classical acupuncture philosophy is different, the dynamics and interrelationships expressed are the same.
Furthermore as an acupuncturist it is my job to take these classical acupuncture concepts, articulate them in a way that relates to our ‘modern paradigm’ (i.e. for the purpose of blogs/education) and most importantly effectively apply them to the body through acupuncture treatment to the ultimate benefit of the patient. Thus I have seen in my clinical acupuncture practice when treating individuals in a ‘pathological’ sympathetic dominant state of being, working on the Ren mai meridian, kidney meridian and liver meridian to be extremely beneficial in regulating neuro-endocrine function when palpatory findings dictate.
I hope this post has shed some light on some basic concepts relating to the autonomic nervous system division and its parasympathetic/sympathetic effects.
As always if any questions arise please feel free to contact me.
Giancarlo Nerini - Licensed Acupuncturist