Breathing and the nervous system

The science of breathing is intimately connected with the autonomic nervous system, bringing its functions under conscious control to affect the body, mind, and emotions.

The autonomic nervous system (ANS) is part of the human nervous system. It behaves like a control system for your vital life functions such as heart rate, respiration rate and digestion, and contains nerves which have special functions related to the glands and visceral organs, regulating the body’s subconscious actions.

Until recently, modern science understood that the autonomic nervous system lay outside of awareness, running entirely unconsciously and autonomously, however, research in the field of neuroscience is now proving that you are able to consciously control your mind by influencing your nervous system through breath – the foundation of the ancient art of Pranayama.

The basics of the nervous system

The autonomic nervous system has three branches – the sympathetic, parasympathetic and enteric nervous systems.  Working automatically, the ANS silently adjusts the balance between the sympathetic and parasympathetic nervous systems. The enteric nervous system, whilst an independent system, works side-by-side with the parasympathetic nervous system.

The job of the autonomic nervous system is to respond to external threats when they arise, to continuously monitor internal body parameters making adjustments to keep them within optimum range. These functions include heart rate (circulatory system), breathing rate (respiratory system), peristalsis (digestive system), neurotransmitters (nervous system), hormone release (endocrine system) and muscle tone (skeleton-muscular system).

The sympathetic nervous system (ANS) – your “fight or flight” response – is designed to respond during stress and emergencies. It is activated when you are physically or emotionally aroused. When activated the body and mind are prepared to either defend or run away from a perceived threat in an automatic physiological reaction to situation (real or imagined) which is threatening or overwhelming.

If perception of danger continues following the activation of the first level of the stress response, the second level of stress response called the “HPA-axis” – consisting of the hypothalamus, pituitary gland and adrenal glands – is initiated and your body remains on high alert. The hypothalamus releases corticotropin-releasing hormone which travels to the pituitary gland where adrenocorticotropic hormone is released, travelling to the adrenal glands triggering the release of cortisol. When the threat passes, the parasympathetic nervous system dampens the stress response and cortisol levels fall.

When the sympathetic nervous system is inactive, the parasympathetic nervous system (PNS) – “rest and digest” response – dominates. The PNS controls bodily processes during ordinary situations.  It is restorative, calms body and mind, brings blood pressure and heart rate to normal, and stimulates your digestive tract to process food and eliminate waste.

The enteric nervous system is also called the “Second Brain”. It consists of 100 million neurons embedded in the walls of your digestive tract and has its own reflexes and senses. This is where the business of digestion occurs, which is why your emotional state drastically affects your gut – for example, you get butterflies in your stomach when you feel anxious.  Conversely, a sensation from the gastrointestinal tract can also affect your emotions – for example, when you have indigestion you may feel disturbed.

The nervous system and healthy living

The balance between the sympathetic and parasympathetic nervous systems determines the overall state of the autonomic nervous system at any given moment. However, whilst stimulation of the SNS takes just a few seconds, the complementary relaxation through stimulation of the PNS requires around twenty minutes. The SNS is an emergency response – a question of life and death – which plays an overly active role in our modern lifestyles. The PNS plays a passive role, since its main job is to moderate the stress response created by the sympathetic branch, and to bring your body back to homeostasis once the emergency has passed.

It is important to note that not only physical stress, but also emotional conditions are responsible for sympathetic nervous system activation. If the SNS remains activated for a long duration without the parasympathetic nervous system getting a chance to calm your body and mind, it can cause havoc in your life and may result in various physical, physiological and emotional disorders. This is the main reason for a significant rise in emotional disorders such as anxiety and depression in the modern world.

How the nervous system affects the Breath

The rate, depth and duration of breathing is adjusted subconsciously by the medulla oblongata – part of the brainstem – based on your body´s requirement for oxygen due to changes in metabolism at any given time, and the level of involvement of different respiratory muscle groups – diaphragm, intercostal, clavicular – changes accordingly. This is the reason you breathe rapidly through the chest when the sympathetic response is stimulated – for example during physical exercise, emotional stress and anxiety. Once the stress response is alleviated and the relaxation response is activated, diaphragmatic breathing should dominate.

There are many other subtler aspects of the breath which impact on the nervous system.

Inhalation vs Exhalation

At a physiological level, when the lungs are being expanded during inhalation, they put pressure on the passage of venous blood from the heart to the lungs, increasing your heart rate. This pressure reduces during exhalation decreasing your heart rate and generating a relaxing effect. This difference in heart rate during the inhalation and exhalation is called Respiratory Sinus Arrhythmia (RSA). A high RSA is a positive indicator of health promoted by deep and slow breathing using the diaphragm.

Left vs right nostril breathing

Did you know that breathing in humans alternates between the left and right nostrils automatically, with one nostril dominating anywhere from a few minutes to a few hours at a time?  According to Yogic science, the left nostril is governed by ida nadi which is associated with parasympathetic tone, and the right nostril is connected to pingala nadi, the sympathetic branch. Therefore, the alternating effects of left and right-nostril breathing are correlated with parasympathetic and sympathetic dominance.

Left vs right hemisphere

From a neuroscience perspective, the dominance of the right hemisphere of the brain corresponds to parasympathetic relaxation stimulation and is associated with increased alpha-wave activity in the EEG of the right cerebral hemisphere.  The left hemisphere corresponds to sympathetic nervous system activation and increased beta wave activity of the left cerebral hemisphere.

Chest vs diaphragmatic breathing

There is a close connection between breathing rhythm and sympathetic/parasympathetic dominance of the autonomic nervous system. When the demand for oxygen is high, your breath rate increases and the muscles in the ribcage dominate in an effort to meet that demand. This is why thoracic breathing – or chest breathing – is associated with dominance of the sympathetic nervous system.  Conversely, we breathe abdominally when the parasympathetic nervous system is in dominance.

Breathing is unique as a physiological function in that it is both autonomic and controllable.  Since your body cannot operate without your breath, if conscious control of the breath is abandoned, then the unconscious part of the mind reflexively takes control and breathing happens automatically. In the case of automatic breathing, the rhythm of the breath automatically changes based on the condition of the autonomic nervous system.

Since the state of the autonomic nervous system controls the rhythm of breathing the reverse is also true – changing your breathing can change the state of your mind and your nervous system. You can experience this by chronically chest breathing – you will be able to create a state of sympathetic nervous system arousal. Similarly, when you are feeling anxious or stressed, diaphragmatic breathing will induce relaxation.

Where Should I Begin?

Here are some examples through which the autonomic nervous system is shifted towards sympathetic tone, thus energizing the body and alerting the mind:

  • Thoracic/clavicular breathing
  • Stimulating Pranayama like Bhastrika and Kapalbhati
  • Breath retention (kumbhaka) following inhalation
  • Breathing through your right nostril

Here are some examples through which the autonomic nervous system is shifted towards parasympathetic tone, thus relaxing the body and calming the mind:

  • Abdominal/diaphragmatic breathing
  • Ujjayi and Viloma II Pranayama
  • Chanting of OM (A-U-M)
  • Breath retention (kumbhaka) after exhalation
  • Breathing through your left nostril

At Breath Evolution, our courses incorporate the teaching of breathing techniques based in pranayama, to achieve specific health and wellness goals.

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