Yoga: Why does it feel so good? Part 4 – Nervous System
This is the fourth and last part of my series on why yoga is so incredibly healthy for us and we finish on the one that is perhaps, the most vital to our survival – our nervous system. Responsible for controlling our body’s actions, thoughts and responses from everything from breathing to going to the toilet, our nervous system directly impacts upon our stress levels. Having a healthy nervous system and being able to ensure it is being used effectively is one of the most important things we can do in this lifetime and we can influence it through our yoga asanas (movement and poses), nidras (meditations), dharana (focus) and pranayama (breathing). Here I explain further…
Why is yoga healthy? (Nervous system)
Yoga is healthy for you aside from building strength and flexibility because it helps equalise both brain hemispheres by activating neural pathways on both sides of the body. The nervous system is complex in that there are a number of sides to it. In yoga, we are concerned with the autonomic nervous system which is the section of the system that we do not consciously control. It is responsible for bodily function such as our breathing and heart rate. This system is divided into our sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) and both are key to our survival.
The sympathetic nervous system is a system for short-term survival. It excites the body, preparing it for action. Any signal of danger or disturbance—real or perceived—can set in motion the stress response. The SNS alerts your heart rate, blood pressure, clotting mechanisms, blood sugar level, respiration, and voluntary muscles to prepare for action. At the same time, it signals your digestive and elimination systems, sensitivity to pain, and other systems not needed for self-defence to slow or shut down. The effects of the SNS are immediate, widespread, and long-lasting. In contrast, the parasympathetic nervous system is a system of long-term survival. It promotes rest and regeneration. The acronym SLUDD succinctly summarises the functions of the
PNS: salivation, lacrimation, urination, defecation, and digestion. In addition, this system redirects blood flow back to the core of the body. The PNS system is characteristically slower to take effect than the SNS, and its effects are less widespread.
In this system of dual innervation, most organs receive nerve impulses from both the sympathetic and parasympathetic nervous systems. While the two divisions are activated under different circumstances, both are vital to our survival and well-being.
In our modern world, it is rare that our survival is under threat however, there are many situations which can activate our stress response as we perceive stressful situations as being a threat to our survival. It is highly detrimental to the body to experience the stress response on a regular basis without being able to work off this negative impact through exercise. We become chronically stressed and exhausted. The nerve impulses from the SNS redirect energy to the muscles and organs needed for immediate survival in an emergency, and away from those needed for longer term survival and reproduction.
The second stage, the resistance reaction, is initiated by hypothalamic releasing hormones, which stimulate the release of cortisol, human growth hormone, and thyroid hormone. By producing increased energy, and by helping the body repair damaged cells and reduce inflammation, these hormones enable the body to continue to fight the stressor after the initial response dissipates.
Most of the time, these two stages suffice to get the body through stressful situations. Sometimes they do not, and the body moves into the exhaustion stage, in which it continues to produce large amounts of stress hormones. Prolonged exposure to these hormones, particularly cortisol, can have devastating effects. A sustained high level of cortisol destroys healthy muscles, bones, and cells, suppresses the immune system, impairs digestion, and weakens endocrine function. The destructive effects of chronic stress put people at greater risk of chronic disease and premature death.
In particular, Yoga techniques offer the possibility of reducing inappropriate activation of the sympathetic nervous system. The calming effects of savasana (corpse pose), Yoga nidra (meditation), and pranayama (breathing) have been widely studied and reported. The effects of these practices provide a great service to many Yoga aspirants by giving them a short-term “time out” from stress, and also by creating positive physiological changes in bodily systems (including the nervous system). For example, deep breathing activates the parasympathetic nervous system, possibly because regular movement of the diaphragm stimulates the vagus nerve. These practices can induce the relaxation response, which provides a healthy respite from chronic stress.
While these techniques are valuable, they may only calm us temporarily. If underlying patterns in our psyches continue to trigger the fight-or-flight response inappropriately, we end up simply repeating the same old patterns. Such patterns are often deep, long-standing, and subconscious. Unless we choose to change them and develop tools to do so, the fallback position is to repeat and reinforce the patterns, making already strong tendencies ever stronger. In Yoga, we can practice repetition to change deeply embedded physical, psychological, or emotional patterns. We can use repetition in meditation to observe and understand our behavior patterns, and then create new ones. Imagine the profound and lasting effects that could result from changing these deeper patterns that affect the way we view ourselves, others, and the world.
Through our thoughts and our actions, we are continually recording patterns on citta. Patanjali shows us that we have the choice of reinforcing old patterns and, thus, repeating the same behaviours, or creating new patterns and changing our behaviour. By choosing to focus the mind, we can end the distractions that cause the mind to be agitated. An agitated state of mind calls up unconscious tendencies associated with the stress response, while a focused mind evokes patterns associated with the parasympathetic, rest and regeneration response.
Each time we consciously focus the mind, ending a vrtti (disturbance), we are reprogramming our individual citta. Patanjali calls this process nirodah parinama. When we do this continually, a new pattern emerges, the old pattern recedes, and we experience the calm flow of transformation described in Sutra III.10. Because transformation is a journey inward, the old pattern being replaced is called the vyutthana (externalisation) samskara.
From a physical perspective, ashtanga yoga makes movement easier by creating neural pathways to make movements reflex actions and therefore, automatic. This enables the body and brain to be at ease, thereby activating the parasympathetic nervous system.