When the bladder fills with urine, sensory nerves send impulses to the brain indicating that the bladder is full. The sensory nerves connect with other nerves in the spinal cord to relay this information. In turn, the brain sends impulses back to the bladder instructing the bladder to empty its contents.
Update Date 10/2/2013
Updated by: Scott Miller, MD, Urologist in private practice in Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.