Sympathetic tone refers to the state of excitation of the sympathetic nervous system, which cannot be precisely measured and is constantly changing. Increased sympathetic tone puts the body into a type of response mode such as flight or attack. It is noticeable, among other things, by an increase in blood pressure, acceleration of the heart rate, constriction of the peripheral blood vessels and a decrease in intestinal activity. The parasympathetic nervous system acts as the main antagonist, providing relaxation and regeneration.
What is sympathetic tone?
Sympathetic tone refers to the state of excitation of the sympathetic nervous system, which cannot be precisely measured and is constantly changing. The term sympathetic tone is used to summarize the state of excitation of the sympathetic nervous system. The sympathetic nervous system, together with its antagonist, the parasympathetic nervous system, is classified as part of the autonomic nervous system. Sympathetic tone cannot be measured precisely and is constantly changing to adapt to the situation at hand. When sympathetic tone increases, the body is put into a heightened response mode and increased physical and muscular readiness to perform. Physiologically, the body is optimally programmed to flee or attack (stress response). However, the flight or fight mode is somewhat detrimental to other functions that are important for survival, so that a phase of high sympathetic tone must be followed by a relaxation phase, which is achieved by increased release of the neurotransmitter acetylcholine via the parasympathetic nervous system. In a healthy person, sympathetic and parasympathetic tonus complement each other and there is a balance between the two antagonists. In phases, the sympathico- or the parasympathetic tone respectively determine the physiological events in the body.
Function and task
Sympathetic tone, which is a measure of the sympathetic state of arousal, was developmentally important for the immediate protection of humans. High sympathetic tone, synonymous with high stress levels, sets off a cascade of short-term physiological changes that optimally prepare humans for flight or attack. The blood vessels supplying the skeletal muscles react by dilating, while vessels of the skin and those of some organs, such as the kidneys, become constricted. With a simultaneous increase in blood pressure and heart rate, improved supply to the muscles is achieved while reducing the risk of bleeding at the periphery in the event of a possible injury. In addition, intestinal peristalsis and urine production are slowed to achieve longer endurance even in the area of necessary excretion. Increased glycolysis via the breakdown of carbohydrates and increased cerebral blood flow couple optimal physical performance with optimal brain performance. Developmentally, the main benefit of sympathetic tone was probably optimal protection from attackers, either by flight or by attack. For both possibilities, a high sympathetic tone equally provides the best physiological preparation. Changing lifestyles in the industrialized world often result in stressors that trigger high sympathetic tone, which sets off the entire physiological cascade. As a rule, however, the stress hormones cannot be reduced by a high physical performance or an endurance performance, because flight or attack would be counterproductive in the situation and even before the stress hormones are reduced, the next stressor already appears. Often, therefore, there is a danger that the body is constantly kept on alert by particular stressors. The original protective mechanism can then turn into a risk for the development of a cardiovascular problem in the form of high blood pressure or other secondary diseases.
Diseases and ailments
High sympathetic tone, which is recognizable by a concentration of stress hormones (epinephrine, norepinephrine) above normal levels, causes a series of short-term physiological changes in the body, all of which are aimed at creating optimal conditions for escape or attack in the event of a threat. In principle, disease-related functional impairments can occur at any point in the wide range of physiological changes.Directly related to sympathetic tone is an inadequate balance between sympathetic and parasympathetic tone. It often leads to an almost permanent dominance of the sympathetic nervous system over the parasympathetic nervous system. As a result, the body has too little opportunity to regenerate, because the body is constantly in a state of alarm and many physiological processes no longer take place in normal mode. Typical complaints resulting from this are nervousness, sleep disturbances with daytime fatigue, cramps and digestive problems. The relatively non-specific symptoms had led many physicians to diagnose vegetative dystonia in the 1950s and even later. Today, the term is controversial among specialists, since in many cases it is “only” a disturbance in the relationship between sympathetic and parasympathetic tone in favor of sympathetic tone. The shifted relationship between the sympathetic and parasympathetic nervous systems is referred to as sympathicotonia. Most likely, sympathicotonia is due to the fact that frequent stressors cause a more or less permanent high concentration of stress hormones that cannot be physically “worked off”, so that some physiological processes only run in alarm mode and cause discomfort. Sympathicotonia also poses risks to the cardiovascular system. The frequent increase in blood pressure due to the frequent release of stress hormones carries the risk that the increased blood pressure and usually also an increased heartbeat rate will become permanent and chronic, i.e., permanent hypertension with all its sequelae will develop. It is very likely that genetic factors play a role in this. Excitability to stressors is highly individual. The sympathetic centers in the spinal cord receive impulses from specific regions in the central nervous system and react by increasing the sympathetic tone. The basic pattern here follows a genetic fixation and is probably only partly acquired through life circumstances.
