When the bladder fills with urine, sensory nerves send impulses to the brain telling it the bladder is full. The nerves connect with other nerves in the spinal cord to relay this information. In turn, the brain sends impulses back to the bladder instructing it to empty its contents.
Review Date 9/7/2021
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.