A healthy nervous system maintains homeostasis by balancing input from both branches of the ANS during activites ranging from relaxing, digesting and sleeping, to waking, walking, feeling excited, and running.
Sympathetic Nervous System Increases:blood pressureheart ratefuel availability (sugar, fats...)adrenalineoxygen circulation to vital organsblood clotting (minimizes loss of blood if wounded)pupil size and peripheral vision (improves vision) Decreases:fuel storage (decreases insulin activity to store glucose, for example)digestionsalivation. Under Normal Circumstances, the Sympathetic Nervous System promotes the ability to be active and the defense mechanism of fight or flight. It affects activites in red. An individual who is exposed to states of SNS dominance has an increased risk for Symptoms and Illnesses listed below, which have long been associated with stress.
The symptoms and illnesses associated with SNS dominance are those of fight/flight, and include: hypertension, hypercholesterolemia, fast arrhythmias, heart disease, type 1 diabetes, sjogren's; anxiety, panic attacks, hypervigilance, poor sleep,...
Increases vigilance and arousal to quickly notice and respond to danger.
Symptoms: hypervigilance; startling easily;nervousness;anxiety;fear;
Illness: chronic or severe anxiety; panic attacks
Increases blood pressure to get blood to the brain and vital organs:
Symptoms: ? white coat high blood pressure;
Illness: hypertension, strokes from prolonged high blood pressure, heart disease; heart attacks
Increases heart rate to circulate fuel and oxygen to vital organs for activity and defense:
Symptoms: fast heart rate
Illness fast arrhythmias (?atrial fibrillation; PSVT?)
Increases fuel availability (sugar, fats...) to the brain, muscles and other organs who need it during exercise and defense. Because insulin promotes food storage, it is inhibited during sns activity to maximize fuel availability.
Symptoms: high blood sugar; high cholesterol;low insulin;
Illness type 1 diabetes, with increased risk for high blood pressure, high cholesterol, heart disease,...; hypercholesterolemia
Increases adrenalineto facilitate changes in blood pressure, heart rate etc
Symptoms: shakiness; palpitations; ?butterflies; difficulty concentrating
Illnesschronic anxiety, panic, hypertension, and others listed here
Increases oxygen circulation to vital organs to provide fuel for activity and defense while decreasing circulation to non-vital organs such as skin, the extremities,...
Symptoms: cold hands and feet;headaches?
Illnessperipheral neuropathy?
Increases blood clotting ,which minimizes blood loss if wounded during defense such as fight/flight
Symptoms: strokes; clotting disorders
Illnessstrokes;
Increases pupil size and peripheral vision to maximize awareness of sources of potential danger.
Symptoms: blurry vision when trying to focus on narrow vision (reading...)
Illnessprolonged visual changes requiring corrective lenses?Due to its participation in generating the well-known fight/flight response, the SNS is the more familiar and the more studied of the two branches of the autonomic nervous system (ANS). Contrary to its name, the fight/flight response, coined by the physiologist Walter Cannon (Ganong, 2001), represents a broad range of mobilization activities. The sympathetic nervous system (SNS) is geared towards mobilization. It is associated with active coping strategies, such as the energized activity utilized to complete a project, fight a foe, or flee a predator. A stronger activation of SNS arousal arises following experiences that are emotionally distressing (Goldstein, 2000) such as the perception of threat. In the face of danger, the SNS facilitates changes in the body that promote survival. These changes include elevations in heart rate to facilitate the rapid circulation of oxygen and glucose to muscles that need fuel to flee or fight, pupil dilatation for better vision, water retention to minimize loss in fluid volume, and increases in the clotting of blood that minimize blood loss in the event of wounding.
Examples of threats that may induce the fight/flight or stress response include those arising within the internal environment, such as in the case of low blood sugar, which represents a global threat to the organism sugar (glucose) is the only food used by the brain (Ganong, 2001). Threat may also be perceived in the external environment, such as occurs when someone comes face to face with a bear, is in an accident, or is threatened by a hurricane. Excitement (an internal stimulus) or a long jog (an external stimulus) may stimulate the same level of sympathetic arousal that is mediated in the face of threat (Braunwald et al., 2001). The context in which threat occurs, the perception of the degree of danger, and the ability to successfully escape from a situation all affect the degree of SNS response.
