Your body’s ability to deal with stress is regulated by the autonomic nervous system (ANS). This system monitors the environmental signals, interprets them, and organizes appropriate automatic behavioural responses. It is composed of a specialized group of neurons that regulate cardiac muscle (the heart), smooth muscles (walls of the visceral organs and blood vessels) and glands.
The autonomic nervous system has two components that balance each other – Protection – the sympathetic nervous system(SNS) and Growth – the parasympathetic nervous system (PNS). What is important to know is that both systems CANNOT operate optimally at the same time. We unavoidably restrict our growth behaviours when we shift into protective mode (stressed).
Protection – the HPA axis and the Immune system
The sympathetic nervous system (SNS) turns UP your nervous system. It helps us handle what we perceive to be emergencies or threatening situations (can include emotional upset as well as physical stress) and is in charge of the flight-or-fight response. The SNS has two systems to protect the body: the Hypothalamus – Pituitary – Adrenals axis (HPA Axis) which responds to perceived external threats, and the Immune system which protects us from threats originating underneath the skin (like attack by virus or bacteria).
1. HPA axis
2. Immune system
Growth – the Vagus Nerve
The parasympathetic nervous system turns DOWN the nervous system and helps us to be calm. It is most active when the body is at rest and not threatened in any way. This division is sometimes called the ‘resting-and-digesting’ system since it is chiefly concerned with promoting normal digestion, with elimination of feces and urine, and with conserving body energy. It promotes relaxation, rest, sleep, and drowsiness by slowing our heart rate, slowing our breathing, constricts the pupils of our eyes, increases the production of saliva in our mouth, and allows us to digest our food and grow.
The vagus nerve is the key instrument of the parasympathetic system. Beginning in the medulla oblongata, the nerve travels to all of the organs of the body sending signals to and from the brain. The two previous posts provide lots of information about the vagus nerve and how to activate the relaxation response. Post 1 – The Vagus Nerve, Post 2 – Activating the Vagus Nerve.
Importance of sleep
A recent survey found that more people are sleeping less than six hours a night, and are having difficulties sleeping (because they are unable to turn off their HPA axis). Chronic sleep loss can contribute to health problems such as weight gain, high blood pressure, and a decrease in the immune system’s power, reports the Harvard Women’s Health Watch.[i]
Some important tips for getting a good night’s sleep and allowing the PNS time to heal and relax are:
|Organ||Sympathetic Stimulation/Stress||Parasympathetic Stimulation/Relax|
|Heart rate||Increased rate and force of heartbeat||Decreases rate; slow and steady|
|Lungs||Dilates bronchioles||Constricts bronchioles|
|Motility||Decreased activity of digestive system||Increased slow muscles mobility (peristalsis) and amount of secretion by digestive system|
|Sphincters (closing valves)||Constriction||Relaxation|
|Gallbladder and bile ducts||Relaxed||Contracted|
|Bladder/Kidneys||Constricts sphincters (prevents voiding)||Relaxes sphincters (allows voiding)|
|Exocrene glands (glands with external secretion)|
|Salivary glands||Slight secretion||Copious secretion|
|Digestive glands||Reduced secretions||Copious secretions containing many enzymes|
|Sweat glands||Secretion||No effect|
|Pancreatic glands||Reduced secretion||Copious secretion[ii]|
Today, we live in a stressed-out world and an increasing body of research suggests that our hyper-vigilant lifestyle is severely impacting the health of our bodies. Daily stressors and emotional upsets are constantly activating the HPA axis causing emotional and physical disharmony that cause major illness such as cardio vascular issues, depression, digestive issues, glucose/insulin resistance. Further, these stressors are not released from the body (as they would be in a fight or flight situation) and can build up to become chronic fears and concerns.
A dynamic balance needs to exist between the two divisions of the autonomic nervous system, so that they can continuously make fine adjustments. As a society we need to find new ways to release our fears and stressors and add relaxation time and techniques to our daily life.
[ii] https://ayurveda.lotusguides.net/en/index.php?p=articles&id=2 and Marieb, Elaine N., Essentials of Human Anatomy & Physiology, p. 269.
Lipton, Bruce. Biology of Belief. Hay House: 2005. Pp. 114-119.