The relief of peeing

The topic is mundane, I know—but who doesn't know the relief, almost pleasure, of emptying your bladder when it's already stretched to the limit? The reason is that holding your pee is hard work for the brain, as well as making you anxious and unable to think about anything else.

Urination is something the brain can do without conscious control. As the bladder fills with urine, information about its state of distension is passed through the nerves to the spinal cord and from there to the urination control center in the brain's pons. Once the bladder is too full, this center automatically initiates emptying.

But peeing at any time, simply because the bladder is full, is not considered civilized. Humans and dogs quickly learn that there is a time and place for peeing thanks to their ability to recognize the sensation of a full bladder and exercise cognitive control over the pontine center of urination.

If the bladder becomes too full, there is no way around it: the safety mechanisms take over, and out goes the urine. But until then, the pontine center of urination is under the control of the prefrontal cortex, which only allows urination when, in addition to being necessary, it is socially acceptable and can happen in a safe place.

The prefrontal cortex, in turn, exercises its control informed by the insular cortex, which represents, among other physiological sensations, the sensation of the bladder filling up. The insula also passes this information on to the cingulate cortex, which monitors the situation and alerts other regions of the brain when things start to get critical. From then on, all you can think about is the nearest bathroom, while the prefrontal cortex holds the fort, literally, keeping the pontine center inhibited.

Once in the bathroom, and with prefrontal blessing, the pontine center switches from sympathetic activity, which keeps the bladder distended and the sphincter contracted, to parasympathetic activation, which contracts the bladder and relaxes the sphincter, allowing urine to pass.

That's why peeing feels so good: in addition to being a state of parasympathetic activation, which relaxes the body, it also relieves your cingulate and prefrontal cortex, which were working hard to keep you tense, in control, and looking for a bathroom. Hence the mental relief of being able to pee. It's like being able to tell a secret and stop suffering about it. Aaaaah...

Excerpt from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in June 2013