Most of the system controlling the bladder lies inside the pelvis, which is shaped like a large bowl. A balloon-shaped muscle located just below the belly button, the bladder stores urine. When you urinate, the muscle tightens up to squeeze the urine out. Urine leaves the body through the urethra, a tube surrounded by two sphincter muscles. The urethra is kept closed by the sphincter muscles squeezing like rubber bands. What are known as pelvic floor muscles under the bladder also help keep the urethra closed.

Once the bladder becomes full, the brain is signaled that you need to get to a bathroom. When the toilet is reached, the brain signals the sphincter and pelvic floor muscles to relax, allowing urine to pass out through the urethra. The bladder tightens up, allowing the urine to flow out of it.

Normal Bladder Control
Having normal bladder control means you urinate only when you need or want to. Good bladder control means that all parts of the system must work in sync:

  • The pelvic muscles must hold up the urethra and bladder
  • The urethra must be open and shut by the sphincter muscles
  • The bladder and pelvic floor muscles must be controlled by the nerves

Losing Control
You begin to lose normal control of your bladder when the muscles become too active. At this point, you may experience urge incontinence.

There are several reasons why your bladder may be too active, some of these include:

  • Nerve damage
  • A bladder infection
  • Alcohol
  • Some medications