Parasympathetic Nervous System

The parasympathetic nervous system is one of the two main parts of the autonomic nervous system - the part of the nervous system that functions without conscious control, regulating functions like heart rate, blood pressure, breathing, and digestion.

The parasympathetic nervous system (PNS) is responsible for bodily functions that take place when you’re at rest. These activities include digestion, lowering heart rate, reducing muscle tension, removing waste, salivating, and sexual arousal (Biology Dictionary, 2017). This is why the PNS is typically referred to as the “rest and digest” system.

The parasympathetic nervous system is active during everyday activity when nothing particularly stressful is going on. It regulates the automatic bodily functions that are essential to keep us going.

The parasympathetic nervous system is also what brings us back to a state of calm after a period of stress. After danger or a perceived threat has passed, the parasympathetic nervous system allows you to calm down by lowering your heart rate and blood pressure, relaxing muscles, and slowing breathing. It brings your systems back to homeostasis, or balance, and allows your body to relax and recuperate (NCI Dictionary, 2023). Slowing things down allows us to conserve energy so we’re ready for future threats where quick action is needed.

Functions

Here are more specifics about what the parasympathetic nervous system does. The parasympathetic nervous system:

Constricts pupils for better near vision

Creates tears to keep eyes lubricated

Increases salivation

Slows heart rate, especially after a stressful experience or after exercise

Constricts airways in the lungs to slow the breathing rate

Facilitates digestion and stimulates intestinal muscles to move things along

Stimulates urination by contracting the bladder

Elicits sexual arousal

Activates the immune system

From the list above, it’s clear the parasympathetic nervous system is involved in some pretty important life-sustaining functions. If it’s not running properly, it can lead to all kinds of health issues. These include gastrointestinal issues, heart rhythm problems, issues with waste removal, and sexual dysfunction.

In addition, many of us experience daily stress or even anxiety which can be triggered by things like work pressures, family concerns, discrimination, or even getting stuck in traffic. So the ability to return to a calm state is critical. Imagine if you were unable to come back down from a stressed-out state. Because of its ability to promote a feeling of calm and well-being, the parasympathetic nervous system plays a crucial role in mental health.

Likewise, the ability of the parasympathetic nervous system to create calm is important for physical health. When we’re in a state of tension, stress hormones like cortisol and adrenaline are released which raise your blood pressure, increase your breathing rate, and create muscle tension. Being in this state frequently contributes to many health problems such as heart disease, diabetes, obesity, and depression (APA, 2010). The parasympathetic nervous system also plays another important role in our physical health by regulating the immune system. It’s involved in controlling inflammation and promoting healing.

Activate the Parasympathetic Nervous System

Although the parasympathetic nervous system generally operates outside of our conscious control, there are some things you can do to activate it. In addition to promoting feelings of calm and relaxation, using these techniques can help reduce the risk of chronic diseases like high blood pressure, heart disease, and digestive disorders. Activating the parasympathetic nervous system can also strengthen the immune system and promote healing. Here are some techniques:

Slow breathing techniques - A study showed that consciously slowing your breath rate to 10 breaths per minute lowers heart rate and blood pressure and promotes relaxation. It was also found to reduce stress and improve mood (Zaccaro et al., 2018).

Yoga - Studies show that yoga can activate the parasympathetic nervous system and reduce the activity of the sympathetic nervous system which relieves anxiety and improves mood (Streeter et al., 2012). It accomplishes this in two ways. First, simply directing your mind to focus on your body in the present moment turns your attention away from worries about the past or future. Also, some specific poses and techniques help bring blood pressure down and induce calm, most involving taking your head below the heart. We’ll get into that in more detail later.

Meditation & Mindfulness - As with yoga, meditation also increases parasympathetic activity and reduces sympathetic activity (Tang et al., 2009). It also does this by turning your mind toward the present moment by watching your thoughts and feelings without judgment. We often use a tool such as watching the breath to give the mind something to focus on. This way we’re less distracted by intrusive thoughts or worries. When distracting thoughts happen (which they will), you gently and without judgment direct your mind back to the breath.

Other methods for activating the parasympathetic nervous system include going for a walk in nature, connecting with friends, laughing, visualizing a peaceful setting, or my favourite, petting your dog.

Notes

The parasympathetic nervous system plays a huge role in health and well-being. With all the stressors we typically experience every day, it can sometimes feel like we’re almost always in that fight or flight mode. Fortunately, there are ways to activate and strengthen the parasympathetic nervous system, which can help us lead a healthier and more well-balanced life.

References

APA. (2010). APA survey raises concern about health impact of stress on children and families. American Psychological Association. Retrieved April 23, 2023.

NCI Dictionary. (2023). NCI Dictionary of Cancer terms. National Cancer Institute. Retrieved April 21, 2023.

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.

Tang, Y.-Y., Ma, Y., Fan, Y., Feng, H., Wang, J., Feng, S., Lu, Q., Hu, B., Lin, Y., Li, J., Zhang, Y., Wang, Y., Zhou, L., & Fan, M. (2009). Central and autonomic nervous system interaction is altered by short-term meditation. Proceedings of the National Academy of Sciences, 106(22), 8865–8870.

Zaccaro, A., Piarulli, A., Laurino, M., Garbella, E., Menicucci, D., Neri, B., & Gemignani, A. (2018). How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing. Frontiers in Human Neuroscience, 12.

Categories: : Therapies