Medical News Today 1-10-19
This article will explain the autonomic nervous system, or ANS, how it works, and the disorders that can affect its functioning.
Anatomy
The nervous system is a collection of cells that send and receive electrical and chemical signals throughout the body.
The nervous system consists of two main parts:
Within the ANS, there are two subsystems that have mostly opposing effects:
The nervous system regulates the internal environment of the body. It is essential for maintaining homeostasis.
Homeostasis refers to the relatively stable and balanced conditions inside the body that are necessary to support life. Some of those that homeostasis regulates include:
The ANS is also involved in the following bodily functions:
If the body perceives a threat in the environment, the sympathetic neurons of the ANS react by:
Factors that affect how it works
The fight or flight response of the ANS evolved to protect the body from dangers around it. However, many stressful aspects of daily life can also trigger this response.
Examples include:
Some drugs can also affect the way the ANS functions. Examples include:
Autonomic disorders affect the functioning of the ANS. They can sometimes occur as a result of the following:
Autonomic disorder symptoms
Autonomic disorders can cause a wide range of symptoms, including:
When to see a doctor
Autonomic disorders can be serious. People who experience symptoms of an autonomic disorder should see a doctor for a full diagnosis.
Talking to a doctor is particularly important for people with diabetes or other conditions that can increase the likelihood of autonomic disorders.
Testing
To diagnose the cause of ANS symptoms, a doctor will first assess a person's medical history for risk factors.
A doctor may also request one or more of the following:
- Anatomy
- Function
- What affects how it works?
- Disorders and causes
- Disorder symptoms
- Seeing a doctor
- Testing
- Summary
This article will explain the autonomic nervous system, or ANS, how it works, and the disorders that can affect its functioning.
Anatomy
The nervous system is a collection of cells that send and receive electrical and chemical signals throughout the body.
The nervous system consists of two main parts:
- The central nervous system: This consists of the brain and spinal cord.
- The peripheral nervous system: This contains all the neurons outside of the central nervous system.
Within the ANS, there are two subsystems that have mostly opposing effects:
- The sympathetic nervous system (SNS): Neurons within the SNS generally prepare the body to react to something in its environment. For example, the SNS may increase heart rate to prepare a person to escape from danger.
- The parasympathetic nervous system (PNS): Parasympathetic neurons mostly regulate bodily functions when a person is at rest.
The nervous system regulates the internal environment of the body. It is essential for maintaining homeostasis.
Homeostasis refers to the relatively stable and balanced conditions inside the body that are necessary to support life. Some of those that homeostasis regulates include:
- body temperature
- blood pressure
- heart rate
- breathing
- metabolism
- blood glucose levels
- blood acidity levels
- water and electrolytes
- digestion
The ANS is also involved in the following bodily functions:
- producing bodily fluids, such as sweat
- urination
- sexual responses
If the body perceives a threat in the environment, the sympathetic neurons of the ANS react by:
- increasing heart rate
- widening the airways to make breathing easier
- releasing stored energy
- increasing strength in the muscles
- slowing digestion and other bodily processes that are less important for taking action
Factors that affect how it works
The fight or flight response of the ANS evolved to protect the body from dangers around it. However, many stressful aspects of daily life can also trigger this response.
Examples include:
- work-related stress
- financial concerns
- relationship problems
Some drugs can also affect the way the ANS functions. Examples include:
- caffeine
- phenylephrine, which doctors use to treat low blood pressure, or hypotension
- clonidine, which doctors use to treat high blood pressure, or hypertension
- albuterol, which helps to relax airway spasms during an acute asthma attack
- the beta-blockers esmolol and labetalol
Autonomic disorders affect the functioning of the ANS. They can sometimes occur as a result of the following:
- aging
- damage to neurons within the ANS
- damage to specific parts of the brain
- diabetes
- peripheral nerve disorder
- Parkinson's disease
- multiple system atrophy (MSA)
- spinal cord disorders
- Lambert-Eaton syndrome
- botulism
- viral infections
- damage to nerves in the neck
Autonomic disorder symptoms
Autonomic disorders can cause a wide range of symptoms, including:
- dizziness and lightheadedness due to orthostatic hypotension (OH), which is a significant drop in blood pressure when standing up after sitting
- reduced or absent sweating, leading to intolerance of heat
- dry eyes and mouth
- digestive issues
- nausea
- vomiting
- constipation
- difficulty urinating
- erectile dysfunction
- pupils being less reactive to light
When to see a doctor
Autonomic disorders can be serious. People who experience symptoms of an autonomic disorder should see a doctor for a full diagnosis.
Talking to a doctor is particularly important for people with diabetes or other conditions that can increase the likelihood of autonomic disorders.
Testing
To diagnose the cause of ANS symptoms, a doctor will first assess a person's medical history for risk factors.
A doctor may also request one or more of the following:
- Tests to detect orthostatic hypotension: A doctor may measure OH using a tilt-table test. In this test, a person lies on a bed that tilts their body at different angles while a machine records their heart rate and blood pressure.
- Electrocardiogram: This test measures electrical activity within the heart.
- Sweat test: This test assesses whether the sweat glands are functioning correctly. A doctor uses electrodes to stimulate the sweat glands and measures the volume of sweat they produce in response to the stimulus.
- Pupillary light reflex test: This test measures how sensitive the pupils are to changes in light.