Merck Manual

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Normal micturition occurs when bladder contraction is coordinated with urethral sphincter relaxation
GU_micturition
Normal micturition occurs when bladder contraction is coordinated with urethral sphincter relaxation

The CNS inhibits voiding until the appropriate time and coordinates and facilitates input from the lower urinary tract to start and complete voiding. The sympathetic system contracts the smooth muscle sphincter. The parasympathetic nervous system contracts the bladder detrusor muscle through cholinergic fibers. The somatic nervous system contracts the striated muscle sphincter through cholinergic fibers from the pudendal nerve. (Adapted from DuBeau CE, Resnick NM with the Massachusetts Department of Health EDUCATE project collaborators: , 1993; used with permission of the authors.)

In these topics
Overview of Voiding