Read on to find out how the sympathetic and parasympathetic systems differ, how much excessive activity of the sympathetic nerve contributes to chronic diseases and how to cause a state of rest and digestion.
You've heard of "fight or flight", but what about its counterpart, "rest and digest"? Read this article to learn more about chronic stress and the fight or flight mode and get tips on how to keep your body relaxed and digested. #healthylifestyle #functionalmedicine #chriskresser
The difference between "Fight or run" and "Rest and digest"
sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) two of the three components autonomic nervous systemwhich controls the body's unconscious functions, such as breathing and digestion, as well as every organ in our body, with the exception of skeletal muscles.
You can recall from Biology 101 that the SNS is responsible for the “fight or run” response to a stressor or danger, while the parasympathetic system controls the functions of rest and assimilation of the body. Here is a brief overview: (1)
Sympathetic nervous system prepares your body to either run from danger or fight back. It is also activated in response to mental or physical stress. During the “hit or run” reaction, the following happens:
- Blood pressure increases
- The blood flow increases to the muscles, lungs and other areas necessary for avoiding perceived danger.
- Blood flow is reduced in the digestive and reproductive systems.
- Stress hormones such as cortisol and neurotransmitters such as adrenaline increase to make us stronger and faster.
- Glucose is quickly released for burning for fast energy.
parasympathetic nervous system is activated after a meal or in response to pleasure, and its physical effects are usually the opposite of those of an SNS reaction:
- Heart rate and slow breathing
- Blood pressure drops
- Intestinal activity increases
- Blood flow increases in the digestive tract
- Neurotransmitters, such as acetylcholine, which regulates muscle contraction, including cardiac muscle, are released
- Stress hormones decrease
Sympathetic vs. parasympathetic: it's all about balance
The sympathetic nervous system interacts with the hypothalamus-pituitary-adrenal axis (HPA) to control the body's response to stress. (2) Stress causes the adrenal glands to secrete hormones, including cortisol, adrenaline and norepinephrine, to increase blood pressure and blood sugar levels. After a stressful event, the parasympathetic nervous system should turn on to reduce the production of stress hormone and lower blood pressure by releasing the neurotransmitter acetylcholine, among other things.
To say that SNS and PNS are antagonistic is a simplification. These two systems can work with each other, against each other, or even independently of each other to maintain homeostasis or balance in all body systems. (3) It's all about balance.
Although their lives were not free from stress, our ancestors knew how to relax and rejuvenate. Adoption of their lifestyle and behavior now, as modern people, is the driving force of ancestral health.
Chronic stress, autonomic balance and heart rate variability
Unlike our ancestors, we lead a life often filled with distractions and busyness. Stress can be permanent – you can constantly worry about money or bad relationships, or experience constant stress from work that leaves you connected to your smartphone 24/7, or constantly sleep less than six hours every night, and all this will constantly trigger a sympathetic reaction nervous system "hit or run." Most likely, you are one of eight out of 10 Americans who, according to a 2017 Gallup poll, say they are under stress. (four)
If you suffer from chronic stress, you may experience the following symptoms:
- Reduced immunity
- Trouble sleeping
- Mood Swings
- Sugar and caffeine consumption
- Irritability or lightheadedness between meals
- Food to relieve fatigue
- Dizziness when going from sitting or lying down
- Digestive distress
Chronic stress upsets the balance between the parasympathetic and sympathetic nervous systems.
When you are in the chronic “fight or run” mode, being in this “on” state disrupts the body's response to stress, increasing overall cortisol and disrupting the normal rhythms of cortisol and melatonin. (5, 6, 7)
A good measure of parasympathetic-sympathetic balance is heart rate variability. (8) Unlike heart rate, which shows the average number of beats per minute, heart rate variability measures subtle changes in the time interval between individual beats. Although some wearable health trackers cannot measure heart rate variability, more sophisticated ones like the Oura ring can.
In general, increased heart rate variability indicates improved health and improved vegetative balance between PNS and SNS. Heart rate variability is often referred to as vagal tone, named after the vagus nerve – the longest nerve in the body – which accounts for 75 percent of the entire parasympathetic nervous system. (9) The vagus nerve connects to the heart, lungs, and digestive tract. In fact, the vagus nerve is a critical component of the axis of the intestine and brain, as a direct link between the intestinal microbiome and the brain. (ten)
Eight causes of stress in your body
Our bodies are not designed to withstand constant stress. Hyperactive SNS destroys the HPA axis, causes chronic inflammation and, ultimately, has been associated with a number of chronic health conditions:
1. Cardiovascular diseases
Chronic sympathetic nervous activity increases blood pressure and destructively changes the shape, size and organization of blood vessels. (11, 12) In one study of patients with heart failure, sympathetic nerve activity was an independent predictor of one-year cardiac death. (13)
2. Insulin resistance and type 2 diabetes
To provide quick energy from a predator, the body’s response to a fight or flight increases blood glucose levels, and chronically elevated levels can lead to insulin resistance. (14) People with type 2 diabetes often show sympathetic hyperactivity. (15, 16)
People who are obese have an increased sympathetic nervous activity and an increased level of norepinephrine compared with a healthy weight. (17, 18, 19)
4. Weakened immune system
Both SNS and PNS regulate the immune system in various ways. High levels of cortisol as a result of continuous stimulation of SNS can suppress immune function, and overactive SNS can shift the body’s immune balance to be sensitive to autoimmune conditions such as rheumatoid arthritis. (20, 21, 22)
5. Kidney disease
Sympathetic nerve receptors are abundantly present in the kidneys, and excessive SNS activity can disrupt sodium and water homeostasis, which leads to an increase in blood pressure and kidney disease. (23, 24, 25)
6. Depression, anxiety and other imbalances of mood
Due to the effect of the parasympathetic nerve on the vagus nerve, a sedentary PNS may contribute to an imbalance of mood. In addition, the autonomic nervous system mediates inflammation and an immune response, both of which are involved in depression, anxiety, and more. (26, 27, 28)
7. Ulcerative colitis, Crohn's disease and irritable bowel syndrome
We know that stress affects the intestines and that chronic stress leads to hyperactivity of the SNA. The imbalance between SNS and PNS is also associated with ulcerative colitis, Crohn's disease, irritable bowel syndrome and other intestinal problems. (29, 30, 31)
8. poor sleep
This is a vicious cycle: stress can lead to poor sleep, which leads to increased stress and disruption of the natural rhythms of melatonin. Sleep problems are associated with obesity, insulin resistance, heart disease, impaired cognitive function, and many others. (32, 33, 34, 35, 36, 37).
12 ways to cause rest and digest
You may be able to cope with acute stress quite easily (especially if you decide to cope with it), and daily stress often passes with time (traffic rush hour is over, you turn on the project, the “big day” in the calendar comes and goes). But if you struggle with chronic stress for a long period of time, your sympathetic and parasympathetic nervous systems are likely to be in imbalance. Try some of the following activities and tricks to begin to relax and digest regularly:
- Deep breathing: Breathing exercises can increase the tone of the vagus nerve and facilitate digestive motility. (38) Check out my favorite breathing techniques to get started.
- Meditation: It has been shown that meditation, especially mindfulness meditation, increases the activity of the PNS, reduces the activity of the CNS, and improves heart rate variability. (39, 40, 41, 42)
- Massage Therapy: Whether it is a head massage, a hand massage or a deep-body massage of the whole body, this type of touch can improve PNS, as measured by heart rate variability. (43, 44, 45, 46)
- Media fast: Using a smartphone can increase the heart rate and reduce the activity of the autonomic nervous system. (47, 48) Regular breaks to work with tablets, phones, and computers help us maintain balance and focus.
- Acupuncture: If acupuncture is performed by a professional licensed specialist, it can increase the vagus nerve tone and reduce heart rate and inflammation. (49)
- Exercise: The sympathetic nervous system is activated during exercise, but regular exercise correlates with increased vagus tonus and overall health. (50)
- Yoga: Yoga increases the activity of the vagus nerve, combining aspects of exercise, meditation and deep breathing. (51)
- Nature: Regular interaction with nature improves vegetative tone and heart rate variability. (52)
- Pleasure: Pleasure for different people looks different, depending on hobbies and interests, but this is not the same as distractions, such as social networks and snacks, watching TV shows
- Immersion in cold water: Especially after strenuous exercise, splashing the face with cold water can trigger the parasympathetic nervous system. (53, 54, 55)
- Gaping: Exaggerated inhalation and exhalation of a yawn triggers the PNS, probably as well as exercises with controlled breathing. (56, 57)
- Chewing gum: Chewing stimulates digestion, controlled mainly by the parasympathetic nervous system. Chewing gum does the same. (58)