2. Background & Significance The storage and elimination of urine is regulated by neural circuits in the brain and spinal cord to coordinate function between the urinary bladder and the urethra. During the micturition (bladder emptying) reflex, the elimination of urine is facilitated by bladder wall contraction and urethral wall and pelvic floor muscle relaxation. Urine that subsequently flows through the urethra also activates sensory nerves to amplify bladder contractions and maintain efficient bladder emptying. Incomplete voiding and urinary retention occurs when these mechanisms are disrupted or poorly coordinated.