As the bladder fills to between 150 and 300 cc, stretch receptors in the bladder walls are activated, creating the sensation of the need to void. Parasympathetic pelvic nerves transmit this signal to the detrusor muscle, initiating bladder contractions. The greater the amount of urine in the bladder, the stronger the impulse to micturate. Sympathetic nerve innervation of the detrusor muscle and internal sphincter prevents premature
parasympathetic stimulation and maintains the muscle tone of the internal sphincter. Higher-level motor impulses inhibit the voiding reflex by constricting the urethral sphincter and delaying voiding. Generally, ignoring the urge to void prevents release of the external sphincter, and neuron fatigue delays further stimulation of the voiding reflex arc for a few minutes to 1 hour. If the urge to void continues to be ignored, bladder reflex contractions eventually take over and cause involuntary voiding. Although micturition is generally under voluntary control, an overfilled or irritated bladder causes incontinence or the involuntary passage of urine.

The act of staying continent requires that a person have the motivation to do so, the ability to use toilet facilities, adequate mental functioning, and manual dexterity to manage clothing. Approximately 13 million adults over the age of 60 have either transient or chronic urinary incontinence. Complications of urinary incontinence include skin breakdown, depression, caregiver and personal stress, social isolation, and economic hardship caused by the cost of incontinence-related supplies. It is estimated that 50% of institutionalized elderly and 11% to 55% of community-dwelling elderly experience urinary incontinence. As a person ages, bladder capacity, sphincter tone, sensation, and the ability to inhibit detrusor contractions decrease, causing the involuntary passage of urine while the person is awake or, in some instances, asleep.