Figure 1.

(A) Neurocontrol of the lower urinary tract. The sympathetic nerve (SYM) from spinal cord levels T10-L2 innervates the urinary tract via the hypogastric nerve. The parasympathetic nerve (PSYM) from the S2–S4 levels innervates the bladder via the pelvic nerve. The somatic nerve controlling the rhabdosphincter is innervated by the pudendal nerve from Onuf's nucleus in the sacral S2–S4 levels of the spinal cord. (B) Anatomy of the lower urinary tract, the nerves that innervate it and key neurotransmitters. Ach, acetylcholine; NE, norepinephrine; +M3, muscarinic receptor type 3, mainly in the detrusor smooth muscle that contracts the bladder; −β3, β3-adrenergic receptors in the detrusor smooth muscle that relax the bladder during urine storage; +α1, α1 adrenergic receptors that contract the smooth muscle of the internal sphincter; +N, nicotinic receptors that contract the external sphincter (rhabdosphincter).