Brain imaging and the popularisation of the term ‘neuroplasticity’, particularly in relation to mindfulness meditation, has elevated the profile of the autonomic nervous system (ANS) in popular culture, popular science, medicine and biomedical research.
Biomedical research has identified imbalances or dysregulation of the ANS as being present in many conditions including stress, anxiety, depression, personality disorders, post-traumatic stress, chronic pain, metabolic syndrome, degenerative neurological diseases, cardiovascular disease, diabetes, irritable bowel syndrome and fibromyalgia.
The ANS is often depicted and understood as being like a see-saw of opposing sympathetic (flight-fright-freeze) and parasympathetic (rest-digest-restore) states. Sympathetic and parasympathetic innervation affect: pupil constriction and dilation, blood vessel contraction and dilation, muscle tone, attenuation of sound, glandular secretion, peristalsis, digestion and many other physiological processes. ANS balance supports optimal homeostasis.
The biological reality of the ANS is not binary. The ANS is a complex regulatory network consisting of central (brain and brainstem) nuclei, peripheral nerve ganglion and neural networks. These are under massive cortical (conscious) influence and communicate extensively with the hypothalamic pituitary adrenal axis and immune system. The ANS is integral to allostasis and is entangled and inseparable from other physiological systems.
The integrative action of the ANS regulates all thoracic and abdominal organs, blood vessels, peripheral nerves, secretory and salivary glands, connective tissue, and muscle. This integrated action is achieved through dual sympathetic and parasympathetic innervation that include both motor (doing) and sensory (information gathering) nerves. Motor fibres cause specific functional changes in the target organ or tissue – dilation, secretion, lacrimation, contraction. Sensory fibres from the ANS convey information to the central nervous system about the overall physiological state of our body. These nerve fibres include mechanoreceptors, chemoreceptors and receptors that mediate pain and other sensations. This rich information stream contributes to the material sense of self referred to as interoception.
This material self is not static or immutable and lesions, for example, can cause a range of changes.
Even in the absence of specific focal lesions, within the ANS, the current and long term balance of the ANS is palpable and perceptible. Tension, density and motion are palpable and can reveal a persons autonomic state.
Common symptoms that may alert us to possible autonomic imbalance include twitching, lacrimation or dry mucous membranes, non-specific myofascial pain, elevated resting muscle tone, gastrointestinal disturbances, dysfunctional menstruation, dysfunctional breathing, cardiac symptoms, tinnitus and headache.
FEATURED IMAGE:
Wilfred Janig. Integrative action of the autonomic nervous system (2006).