The bladder is a hollow muscular organ that serves as the reservoir for urine. When it fills with urine, the internal pressure sends signals to the brain that it is time to pee. While you can control urination to some degree with voluntary muscles in the urethra, the main muscle in the wall of the bladder called the detrusor muscle is involuntary. When it is time to urinate, the detrusor muscle will contract on its own to fully empty the bladder. Bladder spasms occur when the detrusor muscle contracts spontaneously and often when the bladder is not significantly filled.
When this happens, it can cause:
- Convulsive cramping in the lower abdomen, ranging from mild to severe
- Pressure and/or burning in the urethra
- Urge incontinence (the strong, sudden need to urinate that causes leakage)
Bladder spasms occur when the detrusor muscle contracts spontaneously and often when the bladder is not significantly filled.
SOURCES
TREATING INTERSTITIAL CYSTITIS 