The emergency responses of fight, flight, or freeze have been so important for survival over the millennia that they are built into the human nervous system and also that of animals, like alligators, that branched off much lower on the evolutionary tree. However, these responses can also interfere with making decisions and getting along with others. The need for calming down from anger, fear, or withdrawal has led to the practice of slow, paced breathing as part of relaxation in cognitive-behavioral therapy. But how do these biological responses work?
Brain interactions. A simplified view starts with the amygdala, the small, almond-like structure below the surface of the temporal lobes, which stand out on both left and right sides of the brain. The amygdala stores emotional memories of threatening events and emotional responses, and becomes active during emergency situations or reminders of them. It then sends excitatory nerve impulses to the hypothalamus, located in the central part of the brain, which in turn relays impulses streaming downward through the brain stem and spinal cord to activate the sympathetic nervous system. Increased heart rate can be one result, while others include dilation of the pupils, sweating of the palms, and release of adrenaline from the adrenal gland, along with feelings of anger or anxiety.
The prefrontal cortex (PFC) typically keeps the amygdala under control and is involved in thoughtful evaluation and self-control. In addition, relaxed breathing, letting go of muscle tension, and pleasant mental imagery can slow down heart rate and other emergency responses.
Slow, paced breathing. Many athletes, health-conscious people, target shooters, and active military have practiced a method of slow, paced breathing as a way of calming down when necessary before or during a challenging situation (not to be confused with rapid, intense over-breathing or hyperventilation, often associated with panic episodes). In slow, paced, relaxed breathing, during the exhalation phase, as you breathe out slowly from the belly, the diaphragm moves upward, decreasing the space and increasing the pressure around the lungs and heart to force the air out. Inhalation has the opposite effects. These changes act on the body’s pressure sensors, or baroreceptors, at sites in the heart and nearby blood vessels. Stretch receptors in the lungs and respiratory centers in the brain stem contribute additional signals.
The resulting effects of breathing act on the medulla, the lowest part of the brain stem, leading to reflex controls traveling downward through the vagus nerve to enhance parasympathetic activity that promotes relaxation. At the same time, the sympathetic nervous system quiets down.
Extreme examples of keeping calm in dangerous circumstances are firefighters and Navy SEALs who are taught various methods of controlled, slow breathing to help them deal with the stressful situations they may face (Jorge, R., 2017).
Vagus nerve effects. The vagus nerve acts on the cardiac pacemaker to slow the heart rate during exhalation.The resulting normal heart rate variability, in time with the respiratory rhythm, is greater in children and athletes than in older, sedentary people. You may not be interested in mathematical models, but recent calculations (Ben-Tal and others, 2014) suggest that this slowing is most prominent at about 7 breaths per minute, which translates to about 9 seconds per breath at rest. The rhythmic slowing is associated with respiratory sinus arrhythmia in medical terminology. These observations are not to be confused with the type of arrhythmia or other symptoms that require medical attention. This is not medical advice, which should be provided by a physician or other health-care provider.
Vagal tone and interpersonal communication. The overall activity of the vagus, called vagal tone, can potentially help to control unnecessary fight-flight-freeze responses. Vagal tone has recently attracted increased attention in psychology (Miller, J., Kahle, S., & Hastings, P., 2017). Surprisingly, how it works is not totally understood and the mechanism described here is only one part of the story. However, the slow, regular breathing described here is widely used in clinical practice, and can be an important part of the cognitive-behavioral treatment of anxiety, panic, and anger.
The vagus has a primitive group of nerve fibers that promote freezing to avoid danger, according to the polyvagal theory of psychologist Stephen Porges (2009). A more advanced part of the vagus counteracts the fight-flight response of the sympathetic nervous system, Porges says, where its effect on the heart plays a major role. Furthermore, this part interacts with positive facial and vocal expressions that promote a feeling of calm, safety and well-being.
If this theory is correct, it shows how the bodily forms of relaxation described here interact with well-attuned communication between people. In turbulent times like these this positive social communication becomes even more important.
Ben-Tal. A., Shamailov, S., & Paton, J. (2014). Central regulation of heart rate and the appearance of Respiratory Sinus Arrhythmia: New insights from mathematical modeling. Math Biosci. 255: 71–82.
Miller, J., Kahle, S., & Hastings, P. (2017). Moderate baseline vagal tone predicts greater prosociality in children. Developmental Psychology 53 (2), 274–289 © 2016 American Psychological Association
Porges, S. (2009). The polyvagal theory: New insights into adaptive reactions of the autonomic nervous system. Cleveland Clinic J. Med.76 (Suppl 2): S86–S90.
Jorge, R. (2017). Training minutes: Breathing techniques (video). http://www.fireengineering.com/articles/2017/02/training-minutes-breathing-techniques.html