By Gabrielle Lewis
One of the most wondrous and complex structures of the human body is the nervous system and its role in supporting mental and physical health. In this article, we’ll take a deep dive into the Autonomic Nervous System and how it functions. We’ll also look at its role in optimizing whole person health and stress management, how it can get dysregulated through stressors, and how yoga therapy accesses the Autonomic Nervous System to self-regulate and manage stress.
What Is The Nervous System?
The nervous system is an intricate network of nerves responsible for sending and receiving communication between the brain and all the other cells, tissues, and organs. It is the hardwiring of the body, taking messages from the brain to organs, muscles, and glands.
The nervous system can be divided into two main categories. The Central Nervous System (CNS) is made up of the brain and spinal cord. The Peripheral Nervous System is made up of nerves and glands outside of the brain and spinal cord. Its main function is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body.
The Autonomic Nervous System is a component of the PNS that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. It can be divided into three main subsystems: the Sympathetic Nervous System (SNS), the Parasympathetic Nervous System (PNS), and the Enteric Nervous System (ENS). Today we’re going to focus on the SNS and the PNS.
The Role of the Sympathetic Nervous System
Due to the fast-paced world we’re living in, the Sympathetic Nervous System can often receive a bad reputation. From a yoga therapy perspective, each system in the body has a purpose. Sometimes, due to stress and trauma, that purpose can get thrown off course – which can often be the case with the Sympathetic Nervous System. Yoga therapy works on restoring the equilibrium of the body’s systems through a variety of techniques which we’ll learn more about later in the article.
The Fight or Flight Response
The primary role of the SNS is to provide optimal conditions for response to threat. The SNS controls the organs and glands during the flight or fight response.
When discussing the fight or flight response, let’s picture a classic scene from a David Attenborough wildlife documentary with a predator and prey. Through the prey’s senses, it can tell that there is a predator close by, so it has to make a choice for its survival.
The first option the prey can choose is if they are strong enough to fight. The second option is if they are fast enough to flight (run). There’s often a third response known as freeze which we’ll come back to a little later when discussing the Parasympathetic Nervous System.
This survival response is embedded into human beings as well and is a necessary component for our evolutionary survival needs. Often, we may find ourselves in a situation in which the SNS needs to kick it into gear for survival purposes. When these situations happen often or over a prolonged amount of time, the body becomes conditioned to respond to all situations from a heightened state of alert. This creates an overactive SNS which can result in a variety of mental and physical health conditions.
The Role of the Parasympathetic Nervous System
As a counterbalance to the Sympathetic Nervous System, the Parasympathetic Nervous System restores homeostasis in the body’s systems.
The Rest and Digest Response & The Vagus Nerve
The PNS is often referred to as the rest and digest part of the nervous system. It’s responsible for energy building, food digestion, and assimilation. The vagus nerve is an integral part of the PNS. Vagus comes from the Latin word for “wandering” – it’s the longest cranial nerve that controls the PNS, extending from the brainstem to the large intestine.
The Freeze Response
Neurobiology has shown that when responding to stressors something called hypoarousal can occur. Hypoarousal is is a reduction of nervous system activity. In essence, it’s the body’s way of shutting down when feeling overwhelmed when under threat.
For this reason, hypoarousal is also known as the freeze response. Remember the predator and prey analogy – this third response of freeze often occurs. Prey will freeze and camouflage into their environment if they feel they are not strong enough to fight or fast enough to flight. Once they feel the predator has gone then they vigorously shake their body. They instinctively know the importance of releasing their stress after they have been under threat. The freeze response often occurs in human beings as well. Rather than releasing stress somatically, we have a tendency hold on and store stress. This often manifests in imbalance in the body’s systems, including dysfunction in the organs and glands of the body, which can result in disease.
Polyvagal Theory postulates that part of the vagus nerve might have a role in this response to threat and has been coined as Dorsal Vagal Shutdown. This theory suggests that the back branch of the vagus nerve initiates a protective “freeze” response in the face of severe stress, conserving energy and protecting the body when it perceives an inescapable threat. Some of the techniques including breath regulation used in yoga therapy work specifically on the vagus nerve and restoring the body’s homeostasis.
The Hypothalamic-Pituitary-Adrenal Axis (HPA Axis)
As the body is so interconnected, another of the body’s systems to consider when looking at how we respond to stressors and how yoga therapy works is the Hypothalamic-Pituitary Axis or HPA Axis. The HPA Axis is part of the neuroendocrine system and produces a chain reaction of events that prepares the body for fight or flight when perceiving a potential threat.
The Autonomic Nervous System perceives a threat and triggers the hypothalamus to secrete corticotropin-releasing hormone (CRH). CRH then triggers the anterior pituitary to release adrenocorticotropic hormone (ACTH). ACTH then triggers the adrenal cortex to release cortisol which in turn prepares us to fight or flight. The HPA axis is so intelligently designed, that once the cortisol is released it will stimulate the hypothalamus to stop producing CRH and therefore end the stress response. However, when experiencing frequent stress, the HPA axis can become dysregulated.
Chronic Stress: Symptoms Of A Dysregulated Autonomic Nervous System
Our lives tend to run on autopilot, juggling work and home life which leaves little time to understand the mind-body-spirit connection and how stress and a dysregulated nervous system manifest.
The American Institute of Stress distinguishes four main types of stress:
- acute stress (fight or flight system);
- chronic stress (stress of day to day living – work and family);
- eustress (stress that has positive connotations like getting married or getting promoted);
- distress (stress that has negative connotations like getting divorced or losing a job.
With chronic stress we tend to ignore or push down the feelings that arise, and if left uncontrolled chronic stress can affect our overall health. It can present itself in mental health conditions such as depression, anxiety, panic disorders, and trauma responses.
Chronic stress can also manifest as physical health conditions such as digestive issues, cardiovascular problems, chronic pain, cognitive health conditions such as memory dysfunction, and attention and concentration issues.
Finally, chronic stress can show up as behavioral health conditions such as reacting disproportionately to an experience either by under-reacting or over-reacting, irritability, and sleep disorders.
How Yoga Therapy Supports Stress Management & The Autonomic Nervous System
Yoga therapy combines targeted movement, breath regulation, sound therapy, mindfulness, meditation, and lifestyle choices to support stress management, creating a symbiotic relationship in the autonomic nervous system.
Targeted Movement for Nervous System Regulation
Think back to the predator and prey analogy. Remember how the prey shakes their body after the perceived threat has gone? That’s where the targeted movements in yoga therapy come into play. Movements in yoga therapy are very specifically designed to create homeostasis with the HPA axis and the autonomic nervous system.
A study by Garcia-Sesnich et al. in 2017 that investigated the longitudinal and immediate effects of yoga on salivary levels of cortisol showed a decrease in cortisol levels and significant decrease of perceived stress having both an immediate effect, and after 3 months of practice. Furthermore, a study by Nobuhiko et al. in 2020, found indicators of parasympathetic nerve activity and decreased levels of cortisol after specific yoga movements.
Techniques for Vagal Tone
Vagal tone measures the health of the vagus nerve. Different yoga therapy techniques such as breath regulation, humming, chanting, and sound therapy work on increasing vagal tone which supports a healthy, functioning vagus nerve. In 2024, Budhi et al researched a particular yogic breath known as kapalabhati breath, and found that it can modulate vagal tone and parasympathetic activity and improve working memory performance. They also found that the parasympathetic shift may promote better cardioprotective health and longevity.
Breathwork for Nervous System Regulation & Stress Management
One of the foundations of yoga therapy is diaphragmatic breathing. Many people breathe shallowly and/or paradoxically which contributes to a dysregulated autonomic nervous system. This causes stress and dysfunction mentally and physically. Yoga therapy provides support for diaphragmatic breathing by educating and providing ways to practice and incorporate diaphragmatic breathing into daily life.
Your yoga therapist can also layer on other breath regulation techniques that work on balancing the autonomic nervous system to support stress management and overall mental and physical health. In 2024, Yadal et al. conducted a randomized controlled trial that investigated the effects of yoga-based breathing practices on depression, anxiety, stress and fear in Covid-19 positive hospitalized patients. They found that the experimental group reported better scores on all aspects compared to the control group, demonstrating that yoga-based breathing had a positive impact on mental health.
Conclusion
In summary, the autonomic nervous system plays a pivotal role in our overall well-being. Understanding the intricate balance between the sympathetic and parasympathetic systems is essential for managing stress and promoting optimal health.
Yoga therapy, with its targeted movements, breath regulation, and mindfulness practices, offers a comprehensive approach to cultivating a harmonious relationship with the nervous system. By nurturing the mind-body connection, we can empower ourselves to navigate life’s challenges and manage stress with greater resilience, balance, and vitality.
Yoga Therapy Associates provides private yoga therapy. Contact us today to find out how yoga therapy can help you and to schedule your consultation.
References
- Budhi, R. B., & Singh, D. (2024). The Influence of Kapalabhati on Working Memory and Phasic Heart Rate Variability. Cureus, 16(5), e61027. https://doi.org/10.7759/cureus.61027
- García-Sesnich, J. N., Flores, M. G., Ríos, M. H., & Aravena, J. G. (2017). Longitudinal and Immediate Effect of Kundalini Yoga on Salivary Levels of Cortisol and Activity of Alpha-Amylase and Its Effect on Perceived Stress. International journal of yoga, 10(2), 73–80. https://doi.org/10.4103/ijoy.IJOY_45_16
- Gothe, N. P., Keswani, R. K., & McAuley, E. (2016). Yoga practice improves executive function by attenuating stress levels. Biological psychology, 121(Pt A), 109–116. https://doi.org/10.1016/j.biopsycho.2016.10.010
- Eda, N., Ito, H., & Akama, T. (2020). Beneficial Effects of Yoga Stretching on Salivary Stress Hormones and Parasympathetic Nerve Activity. Journal of sports science & medicine, 19(4), 695–702. https://pubmed.ncbi.nlm.nih.gov/33239943/
- Streeter, C. C., Gerbarg, P. L., Saper, R. B., Ciraulo, D. A., & Brown, R. P. (2012). Effects of yoga on the autonomic nervous system, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder. Medical hypotheses, 78(5), 571–579. https://doi.org/10.1016/j.mehy.2012.01.021
- Yadav, S. S., Saoji, A. A., Somanadhapai, S., Yadav, N. L., Upadhyay, J., Rishi, N. N., & Thapa, R. (2024). Effect of Yoga-based breathing practices on depression, anxiety, stress, and fear of COVID-19 positive hospitalized patients: A randomized controlled trial. Journal of Ayurveda and integrative medicine, 15(2), 100897. https://doi.org/10.1016/j.jaim.2024.100897
- Khalsa, S. B., Cohen, L., McCall, T., Telles, S. (2016). Principles and Practice of Yoga in Health Care. United Kingdom: Jessica Kingsley Publishers.
- American Institute of Stress – https://www.stress.org