Monday, February 8, 2010

What is the Autonomic Nervous System?

I'm looking at the image I added to this blog post and nodding my head. This may be one of those posts that don't require many words. So maybe I'll just highlight the main concepts and let the images and the table below do most of the talking today.

The autonomic nervous system
works 24/7/365, i.e all the time. Humans have very little control over what autonomic nervous system does, with the exception of breathing. Some individuals can be trained with biofeedback techniques to influence, but not control, heart rate and blood pressure.

The autonomic nervous system has three components: the sympathetic nervous system, the parasympathetic nervous system and the lesser known enteric nervous system. The sympathetic nervous system controls the "flight or fight" response in our bodies, the "Oh no, there is a lion! Let's get out of here!" response. The parasympathetic nervous system controls the "rest and digest" response. The enteric nervous system is known as our second brain and is located in our gut, although why we need a second brain surrounding our stomachs is still unknown.

Here is a summary of how the sympathetic and parasympathetic nervous systems effect some of our internal structures and organs (chart courtesy of the Neuroscience for Kids website):

The Autonomic Nervous System
StructureSympathetic StimulationParasympathetic Stimulation
Iris (eye muscle)Pupil dilationPupil constriction
Salivary GlandsSaliva production reducedSaliva production increased
Oral/Nasal MucosaMucus production reducedMucus production increased
HeartHeart rate and force increasedHeart rate and force decreased
LungBronchial muscle relaxedBronchial muscle contracted
StomachPeristalsis reducedGastric juice secreted; motility increased
Small IntestineMotility reducedDigestion increased
Large IntestineMotility reducedSecretions and motility increased
LiverIncreased conversion of
glycogen to glucose
KidneyDecreased urine secretionIncreased urine secretion
Adrenal medullaNorepinephrine and
epinephrine secreted
BladderWall relaxed
Sphincter closed
Wall contracted
Sphincter relaxed

In dysautonomia, the sympathetic and parasympathetic responses become dysregulated. One way to measure the responsiveness of the autonomic nervous system is through a test called a heart rate variability study. You may be surprised to learn that a normal heart does not beat at regularly timed intervals. Apparently looking at a heart beat pattern reveals the state of the autonomic nervous system.

According to the results of my heart beat variability study done back in 2005, my heart does beat in a more regular pattern, which indicates that both my sympathetic and parasympathetic systems have less tone or responsiveness. It also showed that overall my sympathetic nervous system was more active than my parasympathetic nervous system. This explains why the my symptoms of dysautonomia trouble me so much, because my body spends way more time in "fight or flight" than "rest and digest."

If a picture is worth a thousand words, you will now begin to see how disconcerting and uncomfortable it might be to live in a body where all your automatic functions are revved up and out of sync.

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1 comment

Lauren jonczak said...

My daughter's doctor told me that she is going to have to get some autonomic nervous system testing done and I am completely worried. I have been doing a lot of research to get a better understanding. This was very helpful, thanks so much for sharing.