Conventional medicine teaches that the parasympathetic system, through its powers on detrusor muscle contraction and internal sphincter relaxation, leads to micturition. Meanwhile, the sympathetic system does the opposite so the bladder does not push that sweet, gold urine out but holds it in.

Why, then, do people urinate more when they are nervous?

The pontine micturition centre is indeed an important area, one that struts around like a pompous turkey with its chest puffed out, wearing a mauve suit and a top hat. It certainly affects the desire to urinate. However, it is tempered by the all-powerful prefrontal cortex. That old dog!

The trusty prefrontal cortex: this fine specimen of modern decision-making prevents you from running yellow liquid down your leg, however surreptitiously you think it might be happening, while making small talk at a cocktail party or waiting in line at the post office. In short, it keeps socially inappropriate things from occurring at socially inappropriate times.

When the brain is racked by fear, the prefrontal cortex shuts down just a little, despite that possibly being the time you need it the most. No matter, because logic is replaced by emotion!

When the inhibition goes, so too does the bladder.

References

1. Arnold, J., McLeod, N., Thani-Gasalam, R., & Rashid, P. (2012). Overactive bladder syndrome – management and treatment options. Retrieved from https://www.racgp.org.au/afp/2012/november/overactive-bladder-syndrome/
2. Palmer, B. (2011). Can You Be Scared Enough To Pee Your Pants?. Retrieved from https://slate.com/news-and-politics/2011/10/peeing-your-pants-why-do-people-urinate-when-they-re-scared.html
3. Innervation of the Lower Urinary Tract. (2018). Retrieved from http://vanat.cvm.umn.edu/lut/Innervation.html
4. Know your brain: Prefrontal cortex. (2014). Retrieved from https://neuroscientificallychallenged.com/blog/2014/5/16/know-your-brain-prefrontal-cortex