Autonomic Nervous System: How It Works and Autonomic Dysfunction

Medically Reviewed By Seunggu Han, M.D.
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The autonomic nervous system is part of the peripheral nervous system. It controls the muscles of the internal organs and the glands. The autonomic nervous system is responsible for processes such as blood pressure, respiration, and heart rate. Other names for the autonomic nervous system include ANS, involuntary nervous system, and vegetative nervous system.

Read on to learn more about the autonomic nervous system. This guide includes information about the functions of the autonomic nervous system, as well as related symptoms and conditions.

What are the functions of the autonomic nervous system?

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Oleksii Syrotkin/Stocksy United (person appearing is a model and used for illustrative purposes only)

The autonomic nervous system controls involuntary functions. There are two main parts to the autonomic nervous system: the sympathetic nervous system and the parasympathetic nervous system.

Sympathetic nervous system

The sympathetic nervous system, or sympathetic autonomic nervous system, is responsible for the body’s “fight or flight” response. This affects multiple organs, as it redirects oxygen-rich blood to areas of the body involved in intense physical activity.

Learn more about the relationship between the “fight or flight” response and stress and anxiety.

Parasympathetic nervous system

The parasympathetic nervous system is responsible for the body’s “rest and digest” state. This controls:

  • energy conservation
  • digestion
  • muscle relaxation
  • heart rate
  • dilation of blood vessels

What conditions can affect the autonomic nervous system?

When there is a problem with the way the autonomic nervous system works, this is known as autonomic dysfunction.

The autonomic nervous system incorporates many of the body’s organs and functions. Because of this, an individual may experience autonomic dysfunction as a result of more than one condition.

Conditions can relate to:

Inherited conditions

Inherited conditions that can cause autonomic dysfunction include:

Autoimmune conditions

Autoimmune conditions that can cause autonomic dysfunction include:

  • Guillain-Barré syndrome
  • Lambert-Eaton syndrome
  • autoimmune autonomic ganglionopathy
  • myasthenic syndrome
  • Sjögren’s disease
  • rheumatoid arthritis
  • systemic lupus erythematosus

Learn more about autoimmune conditions.

Degenerative neurologic conditions

Degenerative neurological conditions that can cause autonomic dysfunction include:

  • Parkinson’s disease
  • Shy-Drager syndrome
  • pure autonomic failure

Learn about neurological symptoms.


Infections that can cause autonomic dysfunction include:

Other conditions

Other conditions that can cause autonomic dysfunction include:

What symptoms are related to autonomic dysfunction?

Orthostatic hypotension is a common symptom of autonomic dysfunction. This is a type of low blood pressure that occurs when you stand up after sitting or lying down. Symptoms of orthostatic hypotension include:

  • dizziness
  • lightheadedness
  • falls
  • fainting

Around 6% of people experience orthostatic hypotension. It is more common in older adults. Learn more about orthostatic hypotension.

Other symptoms of autonomic dysfunction will depend on the underlying cause or condition and which organs are affected.

Possible symptoms of autonomic dysfunction include:

  • increase or decrease in sweating
  • feeling either hot or cold in some areas or across your whole body
  • constipation, digestion problems, and other gastrointestinal symptoms
  • urinary difficulties
  • sexual dysfunction
  • problems with regulating blood pressure

When should I contact a doctor?

Contact your doctor if you have concerns about symptoms or conditions affecting the autonomic nervous system.

Symptoms of autonomic dysfunction can vary depending on the underlying cause. Your doctor will be able to assess your symptoms and advise on the best steps to take.

How are autonomic nervous system conditions diagnosed?

Autonomic dysfunction can occur due to a wide range of conditions. Because of this, examinations and tests to help with diagnosis can depend on the symptoms you present.

Your doctor may focus on:

  • cardiovascular symptoms
  • urination
  • neurological presentation
  • sweat gland activity

If you experience orthostatic syncope or presyncope, your doctor may suspect cardiovascular autonomic dysfunction. These refer to fainting or feeling faint due to low blood pressure when standing.

Autonomic testing

Autonomic testing helps to determine how well your autonomic nervous system is working. There are different types of autonomic tests, which your doctor will carry out depending on your symptoms.

Autonomic testing can include:

  • Tilt table test: Your doctor will securely strap you to a table. They will monitor your blood pressure and heart rate while they position the table at different angles. Learn more about the tilt table test.
  • Deep breathing test: Your doctor will monitor your heart rate and blood pressure while you breathe deeply.
  • Valsalva maneuver: This is another type of breathing test where you will breathe forcefully through a mouthpiece. Your nose will be pinched shut, and your doctor will monitor your blood pressure and heart rate. Learn more about the Valsalva maneuver.
  • Quantitative sudomotor axon reflex test (QSART): The QSART test is designed to test the nerves that control your ability to sweat. Your doctor will place electrodes on your body to stimulate sweating.
  • Thermoregulatory sweat test (TST): The TST test measures your body’s ability to sweat in warm environments. Your doctor will apply a powder to your skin, then slowly increase the temperature of the room. The powder will change color as you sweat.
  • Bladder ultrasound: Your doctor will carry out a bladder ultrasound after you urinate. They will check to see how much urine is still left in your bladder.

How is autonomic dysfunction treated?

Treatments for autonomic dysfunction can depend on the cause, but they will typically focus on:

  • managing symptoms
  • immunotherapy
  • treating underlying conditions

Examples of treatments include:

  • physical exercise or physical therapy
  • compression stockings for cardiovascular autonomic dysfunction
  • wearing sunglasses for dilated pupils
  • immunotherapy treatments, including immune suppressing drugs, intravenous immunoglobulins, and plasma exchange
  • medication to stabilize blood pressure

Orthostatic hypotension treatments

Treatments for orthostatic hypotension include:

  • changing any medications that may be contributing to your symptoms
  • wearing compression stockings or abdominal binders
  • increasing your intake of salt and water at your doctor’s advice
  • making gradual changes to your posture
  • avoiding walking in hot or humid weather
  • avoiding hot showers and saunas

Medications can also help reduce symptoms of orthostatic hypotension if the above treatments are ineffective. Midodrine, an alpha-adrenergic agonist, and droxidopa, a norepinephrine precursor, have both been approved by the Food and Drug Administration for orthostatic hypotension.

Your doctor will advise you on the best treatment options for your specific condition.

What are the complications of autonomic dysfunction?

You may experience complications as a result of problems with your autonomic nervous system. They can depend on the underlying cause or condition but may include:

Contact your doctor if you have concerns about autonomic dysfunction.


The autonomic nervous system comprises the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is responsible for the body’s “fight or flight” response. The parasympathetic nervous system controls the “rest and digest” state.

Autonomic dysfunction occurs when the autonomic nervous system does not function as it should. This can occur due to an underlying condition. Autonomic dysfunction can result in orthostatic hypotension and other symptoms relating to the body’s autonomic functions.

Contact your doctor if you have concerns about autonomic dysfunction. They can perform autonomic testing to determine the cause of your symptoms.

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Medical Reviewer: Seunggu Han, M.D.
Last Review Date: 2022 Jun 30
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