How Do We Know When to Pee?
It's a very long piece..here's a snippet
If you’ve ever come home after a long day at work, and—just as you unlocked the front door—felt a sudden, even overwhelming urge to go, you’ve experienced the tight link that scientists have long known exists between the brain and bladder. Called latchkey incontinence, this type of urge doesn’t have anything to do with how full your bladder is. (It’s also different from a physical inability to hold urine in when we sneeze, cough, or jump: That common problem, called stress incontinence, usually occurs due to weak pelvic floor muscles.)
Some scientists think that the urgent sensations that characterize overactive bladder syndrome may be conditioned responses like the ones that Russian physiologist Ivan Pavlov created in the 1890s when he trained dogs to associate food with the sound of a metronome. For some people, that conditioning could be years of waiting to get home to urinate so they can use their own bathrooms, Clarkson and her team hypothesize. For others, it might arise from a variety of situations and triggers, like the sound of running water. It’s normal if such intense sensations happen occasionally, but if they happen a lot, researchers consider it a potentially worrisome symptom.
Women with overactive bladders often have unusual patterns of brain activity, Clarkson and other groups have found. In a typical experiment in Clarkson’s lab, study participants lie flat in an fMRI machine while a catheter infuses fluid into the bladder until they say they are feeling full. A technician removes some fluid, then replaces it, repeating the process multiple times.
Using this approach, Clarkson and other researchers have built a model of how the brain controls the bladder, involving regions such as the insula, which processes fullness signals from the bladder, and the prefrontal cortex, which helps determine if it’s an appropriate time and place to pee.
Two additional regions, the supplementary motor area and the anterior cingulate cortex, appear to work together to gauge just how urgent the need to urinate is and execute the pelvic floor muscle contractions that help us hold it until a bathroom is found. These areas tend to be more active in some people with overactive bladder syndrome, possibly contributing to the overwhelming sense of urgency even when their bladders are only partly full. “We think that’s almost like a panic station,” Clarkson says. “When you have urgency, you gotta go.”
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