Since my last article a few months ago, I have had the opportunity to listen to the rest of the We Gotta Thing podcasts.  There is an excellent discussion in Episode 30 in which Jay from That Couple Next Door podcast outlines a lot of the same ideas about erectile dysfunction that I have addressed in these articles.  There are two issues that he mentioned that I would like to comment on. First, he points out that erectile dysfunction, or ED, really implies ongoing problems with erections, not just the occasional trouble “getting it up”.  I completely agree although I have used the term more generally here. Second, Jay goes into some detail about the autonomic nervous system, which is very relevant and which I would like to examine before further discussing the treatment of ED.  In the previous article I stated that the most common reason for ED is the brain. The action of the autonomic nervous system is a major subcategory of the causes of ED which originate between the ears rather than between the legs.

The autonomic nervous system, or as I like to think of it, the “automatic” nervous system, controls the functions of the body that a person doesn’t have to think about.  These functions include heart rate, blood pressure, movement of the digestive system, dilation or constriction of the bronchi, dilation or constriction of the pupils, shunting of blood flow, and many other things.  While the control of each of these systems is complex, the autonomic nervous system can be thought of as having two parts: the sympathetic nervous system and the parasympathetic nervous system.  The sympathetic nervous system is what controls our “fight or flight” response to danger or excitement; when the sympathetic system is active, the heart rate increases, the eyes dilate, the bronchi expand, and blood is shunted to the muscles to prepare for action.  On the other hand, when the parasympathetic nervous system is activated things tend to go in the opposite direction: the heart rate slows, digestion and kidney function increase, sexual arousal increases, and blood is shunted away from the muscles to the intestines and other visceral organs.  Therefore the parasympathetic system is often said to promote the functions of “rest and digest”, or more relevant to our concerns, “feed and breed”.

The relevance to ED is that when the sympathetic system is strongly activated then sexual function, including erection, is suppressed.  This makes sense; if a person is threatened and needs to either fight or flee then blood needs to be sent to the muscles and not wasted on causing an erection!  This is one of the most common causes of occasional erectile dysfunction; if the brain senses that it may be in danger, either physical or psychological, then it is likely to activate the sympathetic system and effectively eliminate the chance of successfully achieving an erection.  

Of course, it is not quite as simple as saying that the parasympathetic system prepares for sex and the sympathetic nervous system suppresses it.  Sexual activity does certainly usually involve an elevated heart rate, and some people are sexually excited by dangerous or risky situations. While the “fight or flight” versus “feed and breed” model is helpful to think about, the system is quite a bit more complex.  Some sympathetic activity is actually required for ejaculation; a common medical school mnemonic is Point and Shoot, for the activity of the parasympathetic and sympathetic nervous system in sexual function.  Nevertheless, it is generally true that if a man is in a situation which on some level he perceives as threatening, either physically or psychologically, then there is a good chance he will not be able to get an erection.  He may not even be consciously aware of this feeling of danger.

In my next article, and the last in this series, I will address the treatment of the various causes of erectile dysfunction.

Stay calm and (so you can be) horny,

Dr. C