What is overactive bladder?
The bladder is a part of your body's urinary system. Every time you eat and drink, your body absorbs liquids. Your kidneys then filter out the waste products from your body's fluids and make urine, which is stored in your bladder. The bladder expands as it fills with urine, and contracts to empty.
Both your brain and your muscles are involved in peeing. When the bladder is full, nerves in your bladder signal the brain. That's when you get the need "to go". Once you reach the toilet, your brain sends a message to the large bladder muscle (the detrusor) to squeeze, or contract. At the same time, your brain tells the sphincter muscles that surround the tube that releases urine from the bladder (your urethra) to relax and let the urine through.
Normally, the bladder muscle is relaxed during filling and the muscles only contract when the bladder is emptying. Bladder control means un urinate only when you want to.