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Oxygen is the most important biologic molecule in the human body. It assists in the ion transfer within the cell membrane and is essential for cellular respiration. Even the smallest fluctuations in our breathing pattern can have an impact on mitochondrial function and our cells membrane potentials. So, deep controlled breathing can reduce stress, anxiety, depression and negative affect. How?
There are two main mechanisms responsible for this:
Autonomic nervous system regulation (ANS) and changes in cell membrane potentials.
The autonomic nervous system is made of the sympathetic (SNS) and parasympathetic nervous system (PsNS). SNS is responsible for your "fight or flight" response. The PsNS is responsible for your "Rest and Digest." Depth of breathing, breathing pattern, and starting lung volume all influence degree of sympathetic inhibition, with slower, deeper breathing being the most powerful. Within the vagus pathway, there are branches which branch into the heart (cardiac vagal motorneurons). These have been shown to decrease their rates of firing during inspiration and fire in the first half of expiration. During a respiratory cycle the heart beat slows during expiration and increases during inspiration. These neurons are located in the nucleus ambiguus (NA) and the dorsal motor nucleus of the vagus (DMNX). Increased activity of the vagus causes the vagus nerve to have a stronger influence. This influence is termed "vagal tone" more vagal tone is linked to decreased stress levels (cortisol), decreased inflammation, and pain.
Slow deep breathing by diaphragmatic control has been shown to cause almost complete sympathetic inhibition. Higher lung volumes leading to the most inhibition, most of this sympatho-inhibatory effect occurring during the second half of inspiration thru the first half of expiration. During inspiration, the sympathetic system accelerates the heart, and during exhalation the vagus secrets ACh slowing heart rate. Oxygen inhalation increases cardiac parasympathetic activity, but also alters gas exchange, influencing ventilation. Slow breathing increases the vagal response of the cardiac baroreflex (pressure) and also modifies gas exchange. The increase in tidal volume, may also strengthen bronchial tone. Modification of the autonomic balance toward a parasympathetic dominance strengthens baroreflexes, resulting in reduced heart rate, reduced blood pressure, increased heart rate variability and increased baroreflex sensitivity, which in turn reduce the load on the heart and cardiovascular system in general.
The relationship between our breathing rate and cardiovascular system is termed “Cardiorespiratory synchronization, (CRS)" Stress decreases CRS and is linked to sympathetic control. Higher levels of CRS have been observed during deep breathing and meditation. This also has been observed to inhibit our amygdala (center for fear) and thalamus (center for sensory and information processing). Changes in emotional states have been shown to change neuronal cell membrane potentials. Oxygen accepts more electrons and is responsible for the proton gradient that occur in the electron transport chain during mitochondrial cellular respiration. After we breath in, there is a wave of positive potentials in the limbic (emotional area) region of the brain. These waves are referred to as respiration-related anxiety potentials (RAPs). RAPs begin in the amygdala in those with high anxiety or stress and in the right temporal pole in low anxiety subjects. RAPs, produced 400-500ms after breathing in, show how emotional states can lead to changes in cellular membrane potential. Stress leads to increased breathing rates, making respiration shallower.This leads to increased membrane potentials and more firing within limbic areas of the brain. These RAPs provide evidence of respiration’s influence on emotion.
Slow, deep breathing affecting cardiorespiratory synchronization can cause normalization in cellular membrane potentials and a generalized decrease in bodily pacemaker firings in areas such as the heart and amygdala. This leads to an inhibition of negative emotions. Breathing techniques are being recommended to be used as first line treatments and supplementary treatments for stress, anxiety, depression, and other emotional disorders. These disorders are typically treated with medications that affect neurotransmitters in the brain, rather than treatments that affect the entire body and brain. Widespread homeostatic changes occur during stress and anxiety so treatments that shift the ANS from sympathetic to parasympathetic states can be very effective.
Some evidence has shown that even a single diaphragmatic breathing session significantly reduces blood pressure, increases heart rate variability (HRV) and oxygenation. It can enhance pulmonary function and improves cardiorespiratory fitness and respiratory muscle strength.
Cortisol can be easily affected by breathing. Cortisol can involuntarily control metabolism, immunity, and some mental processing, including memory and emotional arousal, cognitive processing and attention. It has been suggested that the sympathovagal stress response returns to an optimal balance at 4.5–5.5 breaths per minute in most adults, reducing serum cortisol.
We enter this world with a gasp for air and we leave it without it. Our voluntary control over this reflexive mechanism empowers our bodies, minds, and nervous system. Awareness of our breathing, alone, could potentially explain all of the benefits of meditation discussed throughout the ages. It is a vital part of our human life and is continually being shown to have a tremendous influence on our physiology and ultimately, our quality of life. While a simple blog post cannot cover all there is to know, there is sure more to come over this super interesting topic!
Sources:
1. DOI:: 10.3389/fpsyg.2017.00874
2. DOI:: 10.1007/s10484-015-9279-8
3. DOI: 10.3389/fpsyt.2018.00044