|MadSci Network: Anatomy|
Why do males shiver when they urinate?
Justin, I have actually thought about this question myself sometimes when answering the call and have thought I should do some research on the subject. but it is a tricky item to study. If there is any research already done on this topic I am not aware of it but I have a few comments and observations (guesses).
First, you may have noticed, as others and I have, that the shivering is generally related to how distended the bladder is at the time of micturition (defined as voiding the urine, emptying the bladder and many other more vulgar, and popular, expressions). Since the micturition reflex is relayed through the autonomic nervous system (ANS) and is directly related in strength to the amount of stretch of the bladder, the shivering is probably associated to other ANS reflexes. The sympathetic side of the ANS tends to keep the bladder relaxed and the urethral sphincter contracted. That means that you don’t “pee in your pants” when fighting, fleeing, or taking tests, for example. The parasympathetic side of the ANS tends to cause relaxation of the urethral sphincter and contraction of the bladder so that you void.
It is my thought that the more desperate one becomes in response to a bulging bladder, the more of a general sympathetic outflow of action potential will be generated to keep you dry. This would include the release of the adrenal medulla catacholamines epinephrine, norepinephrine, and dopamine. When the opportunity arises to allow the parasympathetic side of the ANS to take over, the change in catacholamine production might be the cause of the shivering. If you carefully pay attention to your body signals when “taking a leak”, you will notice a blood pressure “rush” and a momentary flushing or euphoria shortly after relaxing the urethral sphincter. This feeling is not altogether bad, but not altogether pleasant either. It might be compared to the feeling one gets when receiving highly emotional news (good or bad). This response is also ANS controlled and in its most extreme forms leads to fainting.
Well, that is my thought on the matter and I hope it is worth more than what you are paying for it but without some solid research there is no way of knowing for sure.
Maybe you will take up the challenge and see what is happening here even though you indicate you are a non-science major. As always there could be benefits from this research. One thing that comes to mind is that this would be a way of naturally increasing ANS release of the catacholamines in clinical situations where catacholamines are needed. A nurse could simply insert a catheter (which is often done anyway in clinical settings) into the bladder and control the amount of bladder receptor stretch by adding sterile water or removing urine from the urinary bladder at will. Just a thought!
If you have no idea what the ANS is and want to know more you should get a good basic anatomy and physiology text from your library and read up on it. It is rather complicated but well worth the study. Some author names of general basic texts that would have this information are: Tortora and Evans; Berne and Levy; Moffitt, Moffitt, and Schauf; Silverthorn; Craft; and on and on. Just go to the library and take a look.
Enjoy your studies, Dr. Swanson
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