Autonomic Innervation of the Bladder: The vesical plexus, the anterior portion of the inferior hypogastric plexus, forms loops around the end portion of the ureter and terminates within the bladder wall. Parasympathetic fibers (derived from pelvic splanchnics) travel through this plexus to provide motor innervation to the detrusor muscle and inhibitory signals to the internal sphincter. Therefore when the sensory fibers (visceral afferent) are stretched, the bladder contracts reflexively and the internal sphincter relaxes so urine can flow to the urethra. Sympathetics, on the other hand, cause vasoconstriction of renal vessels to slow urine formation and maintain contraction of the internal sphincter of the bladder to allow for urinary continence. The fibers of the vesical plexus, which also supply the fundus of the bladder, have offshoots to the seminal vesicle, the ductus deferens and the ejaculatory duct in the male.
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