The Anatomy of The Parasympathetic Nervous System and How to Activate It
The body is always see sawing between the sympathetic and parasympathetic nervous systems, with a natural mechanism always trying to return us to our natural resting state, known as homeostasis.
You may heard of these two systems referred to as the fight, flight or freeze system, or the rest and digest system, respectively. In this article, we will pay close attention to the parasympathetic, or rest and digest system, including the basic anatomy of the nervous system, how it functions and how you can consciously affect your nervous state through various practices like ice baths, breathwork and breathing techniques, exercise, heat therapy, meditation and getting in nature.
What is the Nervous System?
The nervous system is responsible for signalling, controlling, responding and feeling of the body and the world around it.
The parasympathetic nervous system is the part of the nervous system that is responsible for calming things down and returning to a restful state, signalling that everything is safe and sound.
The nervous system as a whole is made up of the central nervous system (CNS) and the peripheral nervous system (PNS). While the CNS consists of the brain and spinal cord, the PNS is made up of the somatic nervous system and the autonomic nervous system, which is where the parasympathetic nervous system resides, so to speak.
While the somatic nervous system plays a part in voluntary actions like many of those associated with deliberate movement, the autonomic nervous system is responsible for many involuntary actions like breathing, sneezing, emotional responses, and other internal organ functioning that we don’t see or necessarily notice.
What is amazing is that while it was widely viewed that we could not affect our autonomic nervous system, famous studies on Wim Hof have showed otherwise and doing things like ice baths and breathing techniques offer a conscious and deliberate means to activating the PNS and even voluntarily affecting our immune response.
Ways To Activate The Parasympathetic Nervous System
Activating the parasympathetic nervous system can be a difficult task in a world of high work stress, prevalence of social media and chronic use of stress promoting digital devices, other emotional and life stressors, trauma and other natural challenges.
Of course, if everything is operating normally, the body and mind are capable of a natural shift in and out of sympathetic and parasympathetic states. But, we can become stuck in a chronically sympathetic state where stress is high and the fight or flight response is ‘stuck’ on.
Of course, anyone who has experienced trauma either physical or emotional should always seek help and advice from a medical professional who can offer rehabilitation through physical, emotional and even pharmaceutical therapy, but there are also non-invasive practices that can help us activate the parasympathetic nervous system.
Stimulating The Vagus Nerve
The vagus nerve has an important relationship with the parasympathetic nervous system. Low vagal tone can be associated with people in a chronically sympathetic nervous state. Cold water immersion, especially submerging the face in the cold water, is a reliable way to stimulate the vagus nerve.
The mammalian dive reflex that occurs when we submerge the face for a period in water, can help to stimulate the vagus nerve, relaxing the nervous system into a parasympathetic state.
Ice Baths and Cold Plunge
The interesting thing about cold water immersion is that, initially the extreme cold water causes a stress response on the body characterised by increased breathing, heart rate, blood pressure, pupil dilation and other noticeable physiological responses. Inside the body there are also releases of cortisol, epinephrine and norepinephrine sending signals to the mind and body to remove itself from the situation.
It is after this period of activation of the sympathetic, fight or flight state, that we move into a parasympathetic state from taking ice baths. By taking a regular cold plunge, the research shows that “cold habituation lowers sympathetic activation and causes a shift toward increased parasympathetic activity”, which is why so many people report feelings of positive mood, better sleep, improved mental health and other general wellbeing indicators from cold exposure.
Diaphragmatic Breathing and Physiological Sighing
Various breathing techniques including diaphragmatic breathing and the ‘physiological sigh’ or ‘cyclical sigh’, as described by Dr Andrew Huberman, can reliably shift you into a parasympathetic state.
It has long been known that consciously focussing on the breath, using various methods, is a key to voluntarily influencing the state of your nervous system and affecting stress and mood.
Diaphragmatic breathing and deep breathing can be used as an effective way to activate the parasympathetic nervous system. It is a breathing technique backed up by science, which indicates that diaphragmatic breathing can “trigger body relaxation responses and benefit both physical and mental health”.
At a basic level, diaphragmatic breathing encompasses a variety of other breathing methods, and is characterised by the use of the diaphragm to drive the breath with a rising belly on the inhale.
The physiological sigh or cyclic sighing is another breathing method that has been shown to be a reliable way to promote a state of ‘rest and digest’. Breathing practice is currently used for treatment of PTSD, motion disorders, phobias and other mental health conditions. There is even evidence that a single breathing practice can significantly reduce blood pressure and improve heart rate variability (HRV).
The physiological sigh is a breathing technique that helps reduce stress and anxiety, according to new research, by promoting the activation of the parasympathetic nervous system. The physiological sigh involves taking a full inhale, followed by another small inhale, before a sighing exhale.
Andrew Huberman explaining the physiological sigh
Conclusion
There is a growing interest in people seeking non-pharmacological methods of regulating their mood and mental health.
The nervous system is an essential function of the human body and our existence. Although it is completely normal to shift periodically between the sympathetic and parasympathetic nervous system, it can be the case that we become chronically tilted toward the sympathetic state.
With the obviously negative effects of this stressed state on our overall health, it is important to explore ways to maintain normal functioning of the nervous system. By using non-invasive techniques like cold plunge, breathing techniques, meditation, yoga and immersing in nature, it is possible to return to our natural resting state by encouraging the parasympathetic nervous state.
