Autonomic Nervous System

What is the autonomic nervous system?

The autonomic nervous system (ANS) is a regulatory branch of the central nervous system that helps people adapt to changes in their environment. It adjusts or modifies some functions in response to stress. The ANS helps regulate...

blood vessels' size and blood pressure
the heart's electrical activity and ability to contract
the bronchium's (BRON'ke-um) diameter (and thus air flow) in the lungs
The ANS also regulates the movement and work of the stomach, intestine and salivary glands, the secretion of insulin and the urinary and sexual functions. The ANS acts through a balance of its two components, the sympathetic nervous system and parasympathetic nervous system.
What is autonomic failure?

Malfunction of the ANS is called autonomic failure. It results from an imbalance between the sympathetic and parasympathetic divisions. Aging is associated with several abnormalities in ANS function that can impair elderly people's adaptation to stress.

The most common signs of ANS impairment are ...

a drop in blood pressure when a person is standing or stands up suddenly (orthostatic hypotension) or
a drop in blood pressure within one hour of eating a meal (postprandial hypotension).
The drop in blood pressure causes inadequate blood flow to the brain. That's why it's common for people with this problem to feel dizzy or lightheaded. These conditions occur more often in people with high blood pressure.
Several abnormalities make normal elderly people more likely to have low blood pressure. The onset of disease in old age, such as diabetes, stroke and Parkinson's disease, as well as medications used to treat them, may have other adverse effects in the ANS that are obvious in the cardiovascular system.

How is autonomic failure diagnosed and treated?

There are many tests of the ANS. Most of them easy to perform but hard to interpret individually. The most valuable diagnostic resources are a carefully taken history and a physical exam.

So far there's no cure for autonomic disorders. Still, several physical measures and drugs can help people with autonomic failure prevent low blood pressure or feel less uncomfortable during episodes.

Applying external pressure to the lower half of the body helps prevent blood from pooling in the legs. This maintains blood pressure and improves blood flow to the brain. Custom-fitted counterpressure support garments are used for this.
Physical maneuvers are easy to apply and effective in combating standing dizziness. Leg-crossing, squatting, abdominal compression and bending forward are examples of these maneuvers.
Fludrocortisone (FLOO'dro-COR'tih-sOn) is a drug that's been very successful in retaining water and maintaining blood pressure in autonomic failure. Many patients respond to a combination of the maneuvers listed above and fludrocortisone. For more severe cases, further drug intervention is required.