# sympathetic nervous system | Symptoms, Causes, Tests and Treatment | OSANG > The sympathetic nervous system is the nervous system that quickly prepares the body for dangerous or stressful situations. It begins in the chest and lumbar region of th… - Official page: https://osns.co.kr/en/encyclopedia/sympathetic-nervous-system - Organization: OSANG Neurosurgery ## Page content Autonomic Medicine ## sympathetic nervous system Sympathetic Nervous System The sympathetic nervous system is a branch of the autonomic nervous system and is a nervous system that activates the body by inducing fight-or-flight responses such as increased heart rate, increased blood pressure, and bronchial dilatation in crisis situations. ## At a glance The sympathetic nervous system is the nervous system that quickly prepares the body for dangerous or stressful situations. It begins in the chest and lumbar region of the spinal cord and connects to almost all organs, including the heart, lungs, blood vessels, and digestive system. When the sympathetic nervous system is activated, the heart beats faster, blood pressure rises, pupils enlarge, and digestive functions are suppressed. This response is essential in coping with a crisis, but if the sympathetic nervous system is overly stimulated due to chronic stress, various symptoms such as palpitations, anxiety, insomnia, and indigestion may appear. Heart rate variability (HRV) testing can be used to evaluate sympathetic nerve activity. - 01Definition and Overview - 02anatomy - 03function - 04Symptoms of sympathetic nerve abnormalities - 05Inspection method - 06life management ## Definition and Overview The sympathetic nervous system is one of the two major divisions that make up the autonomic nervous system. It is responsible for the fight-or-flight response, which quickly activates the body in crisis situations. The concept of the sympathetic nervous system originates from the word sympatheia, which means ‘empathy’ in ancient Greek medicine. The term used to describe the phenomenon in which a disease in one organ affects another organ later became established as an anatomical term referring to a branch of the autonomic nervous system. The sympathetic nervous system is distributed to almost all organs, including the heart, lungs, blood vessels, gastrointestinal tract, bladder, eyes, and sweat glands. It is continuously involved in maintaining everyday bodily functions, such as standing, exercising, and regulating body temperature, as well as in emergency situations. ## anatomy The neuron cell bodies of the sympathetic nerves are located in the thoracic and lumbar regions of the spinal cord, specifically in the intermediolateral cell column between the first thoracic vertebra (T1) and the second lumbar vertebra (L2). For this reason, the sympathetic nervous system is also called the thoracolumbar system. Sympathetic nerve fibers from the spinal cord enter the sympathetic ganglia that line the spine. This ganglion is connected like a chain on both sides of the spine from the neck to the tailbone and is called the sympathetic trunk. There are approximately 22 to 23 ganglia on both sides of the sympathetic nerve trunk. The sympathetic pathway consists of two stages. The first level nerve (preganglionic nerve) extends from the spinal cord to the ganglion and uses acetylcholine as a signaling substance. The second level nerve (postganglionic nerve) extends from the ganglion to the target organ and uses norepinephrine as its main signaling substance. The exception is the adrenal medulla, which is directly connected to the preganglionic nerve without the postganglionic nerve. From the adrenal medulla, epinephrine (about 80%) and norepinephrine (about 20%) are secreted directly into the bloodstream and act throughout the body. ## function The core function of the sympathetic nervous system is to prepare the body to respond immediately in crisis situations. This is called the fight-or-flight response. When the sympathetic nervous system is activated, the following changes occur: - Heart: Heart rate and contractility increase, increasing blood supply - Blood vessels: Blood vessels in the skin and digestive organs constrict, while blood vessels in skeletal muscles and the heart dilate. - Breathing: The bronchi expand and oxygen intake increases. - Eyes: Pupils are enlarged (mydriasis), widening the field of view. - Metabolism: Increased release of glucose from the liver increases energy supply - Digestion: Gastrointestinal motility and secretion of digestive juices are suppressed. - Sweat glands: Increased sweating to regulate body temperature This response allows the body to move quickly, focus, and use energy efficiently in crisis situations. The sympathetic nervous system doesn't only work in emergency situations. It is continuously involved in maintaining daily homeostasis, such as maintaining blood pressure by constricting blood vessels in the lower extremities when standing, increasing heart rate during exercise, and narrowing skin blood vessels when cold. ## Symptoms of sympathetic nerve abnormalities When the activity of the sympathetic nervous system is too high or too low, various symptoms occur. The following symptoms are common in sympathetic overactivity: - Palpitations: Feeling that the heart is beating fast even when resting. - Increased blood pressure: Chronic sympathetic hyperactivity is a risk factor for high blood pressure. According to studies, sympathetic nerve hyperactivity is observed in approximately 40-65% of patients with essential hypertension. - Excessive sweating: Abnormally excessive sweating on the palms, soles, armpits, etc. - Anxiety/Nervousness: Physical symptoms caused by hyperactivity of the sympathetic nervous system worsen anxiety. - Insomnia: Initiating and maintaining sleep becomes difficult in a state of sympathetic dominance. - Indigestion: When the sympathetic nervous system is hyperactive, gastrointestinal tract movement and secretion of digestive juices are suppressed. When sympathetic nerve function declines, the following symptoms appear: - Orthostatic hypotension: When standing up, blood vessels do not contract sufficiently, resulting in dizziness or fainting. - Reduced sweating: Difficulty regulating body temperature, increasing the risk of heatstroke in hot environments According to heart rate variability (HRV) studies, autonomic imbalance (sympathetic hyperactivity, parasympathetic inhibition) is significantly associated with increased cardiovascular disease mortality. ## Inspection method The main tests to evaluate sympathetic nerve function are as follows. - Heart rate variability (HRV) analysis: Measures minute changes in heartbeat intervals to determine the balance of sympathetic and parasympathetic nerves. In HRV frequency analysis, the low frequency (LF, 0.04~0.15Hz) component is related to sympathetic nerve activity, and a high LF/HF ratio suggests sympathetic nerve dominance. - Tilt table test: Tilt from a lying down position to a standing position and observe changes in blood pressure and heart rate. Normally, when you stand up, the sympathetic nerves should be activated, blood vessels should constrict, and your heart rate should increase appropriately. - Valsalva maneuver: Analyze blood pressure and heart rate responses after closing the nose and mouth and exhaling forcefully. If sympathetic nerve function is normal, reflex vasoconstriction and increased heart rate are observed when blood pressure decreases. - Blood and urine catecholamine test: Directly evaluates the level of sympathetic nerve activity by measuring norepinephrine and epinephrine concentrations. - Sympathetic skin response (SSR): Evaluates the function of sympathetic nerve endings by measuring the sweating response to electrical stimulation. ## life management Lifestyle rules for alleviating sympathetic nerve overactivity and maintaining autonomic nervous system balance are as follows. - Aerobic exercise: Walking, swimming, or cycling for more than 30 minutes, 3 to 5 times a week, reduces sympathetic nerve hyperactivity and improves parasympathetic nerve function. Research results have reported that 12 weeks of regular aerobic exercise significantly improves HRV. - Abdominal breathing: Slow, deep abdominal breathing (6 times per minute) stimulates the vagus nerve and suppresses sympathetic nerve activity. - Sleep hygiene: Regular sleep of 7 to 8 hours a day is essential for autonomic recovery. Lack of sleep is a major cause of sympathetic hyperactivity. - Limit caffeine and alcohol: Excessive caffeine stimulates the sympathetic nervous system, and alcohol disturbs the balance of the autonomic nervous system. - Stress management: Meditation, progressive muscle relaxation, and regular leisure activities can help prevent chronic sympathetic overactivity. - Water intake: Sufficient water intake of 1.5 to 2 liters per day maintains blood volume and reduces the excessive compensation response of the sympathetic nervous system. If symptoms persist or interfere with daily life, it is recommended to consult an autonomic neurologist. ## Frequently asked questions ### Q01What is the sympathetic nervous system? The sympathetic nervous system is a branch of the autonomic nervous system that prepares the body to respond quickly in dangerous or stressful situations by speeding up the heart rate, raising blood pressure, and concentrating blood flow to the muscles. You can commonly understand this as ‘battle mode nerves.’ ### Q02What symptoms occur when the sympathetic nervous system is overactivated? If the sympathetic nervous system is overly activated, palpitations, chest tightness, hand tremors, cold sweat, anxiety, insomnia, indigestion, and increased blood pressure may occur. If these symptoms persist, we recommend that you seek professional consultation, including an autonomic nerve test. ### Q03What is the difference between the sympathetic and parasympathetic nervous systems? The sympathetic nervous system activates the body in situations of stress or crisis, and the parasympathetic nervous system restores the body in a stable state. The sympathetic nervous system increases heart rate and inhibits digestion, while the parasympathetic nervous system slows heart rate and promotes digestion. Proper balance between these two nerves is key to maintaining good health. ### Q04How is sympathetic nerve function tested? Heart rate variability (HRV) testing is a representative non-invasive evaluation method. In HRV analysis, a high LF/HF ratio suggests a state of sympathetic dominance. In addition, the sympathetic response is also evaluated through tilt-table tests and Valsalva maneuvers. This is a test that can be performed easily and painlessly. ### Q05What causes the sympathetic nervous system to become overactive? Chronic stress, lack of sleep, excessive caffeine consumption, anxiety disorders, and pain disorders are common causes. In some cases, endocrine diseases such as hyperthyroidism or pheochromocytoma may be the cause, so if symptoms persist, it is important to accurately determine the cause. ### Q06What can I do to reduce sympathetic overactivity? Regular aerobic exercise, abdominal breathing, and meditation help relieve sympathetic hyperactivity. Be sure to get enough sleep (7-8 hours) and limit caffeine. If your symptoms are severe, you may want to consider neuromodulation treatment such as medication or stellate ganglion block through consultation with a specialist. ## Related articles - Irritable Bowel Syndrome - Aging and autonomic nervous system - Autonomic dysfunction after stroke - Pupillary Dysfunction This article provides general medical information and does not replace an individual diagnosis or treatment plan. Please seek a medical assessment if symptoms persist. ## Important notice This Markdown alternative helps search and AI tools understand the public page accurately. It provides general health information and does not replace an individual diagnosis or treatment.