Heart Rate Vulnerability

Heart rate variability (HRV) measures the overall health and balance of the autonomic nervous system. The automonic nervous system is composed of three main parts; the sympathetic system which governs “fight and flight,” the parasympathetic system, which is thought of as “rest and digest” and the enteric nervous system that regulates the complex task of digestion, absorption and defense at the level of the intestinal mucosa.
The Autonomic Nervous System (ANS) function is closely tied to adrenal function and overall stress management. It is the autonomic nervous system that continuously monitor and alters the internal workings of your body to maintain “homeodynamic balance.” Homeodynamic balance is the process of maintaining a healthy internal state, despite our complex, ever-changing environment.
Below are lists of functions that the ANS is responsible for. When your ANS is out of balance, your body will not perform these tasks as well as it should.

Specific functions of the sympathetic nervous system:

•  Promotes a “fight or flight” response, corresponds with arousal and energy generation, and inhibits digestion
•  Diverts blood flow away from the gastro-intestinal (GI) tract and skin via vasoconstriction
•  Blood flow to skeletal muscles and the lungs is enhanced (by as much as 1200% in the case of skeletal muscles)
•  Dilates bronchioles of the lung, which allows for greater alveolar oxygen exchange
•  Increases heart rate and the contractility of cardiac cells (myocytes), thereby providing a mechanism for enhanced blood flow to skeletal muscles
•  Dilates pupils and relaxes the ciliary muscle to the lens, allowing more light to enter the eye and far vision
•  Provides vasodilation for the coronary vessels of the heart
•  Constricts all the intestinal sphincters and the urinary sphincter
•  Inhibits peristalsis of the GI Tract

•  The parasympathetic nervous system can also constrict the bronchiolar diameter when the need for oxygen has diminished
•  Dedicated cardiac branches of the vagus and thoracic spinal accessory nerves impart parasympathetic control of the heart (myocardium)
•  During accommodation, the parasympathetic nervous system causes constriction of the pupil and contraction of the ciliary muscle to the lens, allowing for closer vision
•  The parasympathetic nervous system stimulates salivary gland secretion, and accelerates peristalsis, mediating digestion of food and, indirectly, the absorption of nutrients

Specific function of the parasympathetic nervous system:

•  Promotes a “rest and digest” response, promotes calming of the nerves, and enhances digestion
•  The parasympathetic nerves dilate blood vessels leading to the GI tract, increasing blood flow (this is important following the consumption of food, due to the greater metabolic demands placed on the body by the gut)

Specific functions at the enteric nervous system:

•  Control of Motility
•  Regulation of fluid exchange and local blood flow
•  Regulation of gastric and pancreatic secretion
•  Regulation of gastrointestinal endocrine cells
•  Defense reactions
•  Entero-enteric reflexes
•  ENS-CNS interactions (enteric nervous system-central nervous system interactions)
•  Neuro-immune interactions