You already know mostly everything about how the system looks. But how does it work? Who tells the gate at the bottom of the reservoir to open or close and how can our urinary system (when it is working right) allow us to remain dry and “take a leak” only at desired times? This is where the bladder, the pelvic floor, the lower urinary system and its supporting mechanism are connected or rather integrated with the nervous system.

How does my body know when I have to go?

We have described the lower urinary tract as a gated reservoir much like a dam. Even the most sophisticated dam cannot operate without information command systems and ways to deliver orders to its different parts including the gate. Every dam has a control headquarter where information regarding the climate, future precipitation, the level of the water in the reservoir and so on is processed. Once a decision has been made to open or close the gate, the order is forwarded to the gate itself using a communication delivery system of some kind such as electrical cables and relay stations.

We control our bladders in a very similar way. We need input. We need information and this is being gathered and processed all the time. Special sensors (those are the receptors mentioned before because they receive information) are located in the wall of the bladder. They gather information on how full our bladder is. This information is delivered through our electrical cables (the neurons) to the spinal cord (our relay station) and into the brain. This is how you know your bladder is full.

You can be more dramatically informed: The message can be your bladder is really full, and you need to go now (or an urge). 

A last an urgent warning message is conveyed, when you have to go urgently, you know that the gates will open no matter what the circumstances are (strong urge). Information is flowing, not only from the body itself, but externally as well. External input can range from the absolutely uncomfortable: “I am at a meeting with my manager now, so I cannot use the restroom” or “I am giving a talk in front of an audience”, to the less uncomfortable but no less compelling reason: “the movie I am watching is really interesting and I don’t want to miss it.”

Our external situation affects our decision to delay using the bathroom to a more appropriate or convenient time. That is when information is flowing down the communication system (nervous system) back to your bladder: “Hold your horses” or at least your water.

But the commanding system (our brain) can send other orders. Take the following situation as an example.

You finally arrive home after a long day during which you could not get to the bathroom. You put your key in the lock, open your door, you rush to the bathroom, pull down your pants and at last you are sitting on the commode and are ready to go. But all of these steps are not enough; the real process has still to take place. Your brain is sending these orders: Release the pelvic floor, open the gate (relax the urinary sphincter), and contract the bladder. Finally, you are voiding. What a relief!

Holding it in and letting it go

Considering all the external and internal information your body has to process, your bladder and pelvic floor will always be in one of two states or phases:

The first stage is the storing phase in which the bladder is holding and storing urine. In this phase the muscle in the wall of the bladder is relaxed and the external sphincter is in the closed gate mode.