The Urinary System: Urinary Retention Essay

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Urination is controlled by a complex central nervous system mechanism that coordinates urine storage and release by the regulation of smooth muscle in the bladder and urethra. Bladder storage, emptying and coordinated urinary sphincter activity , are controlled by the sympathetic, parasympathetic, and somatic nervous systems. Parasympathetic nerves in the spinal cord (S2-S4) act to contract the bladder and relax the urethra through the release of acetylcholine, which excites smooth muscle muscarinic receptors (17). This causes urination through detrusor contraction. Postganglionic sympathetic neurons (T11- L2) . release noradrenaline causing bladder base contractions and relaxation of the bladder body, mediated by acetylcholine on…show more content…
Urination is controlled by a complex central nervous system mechanism that coordinates urine storage and release by the regulation of smooth muscle in the bladder and urethra. Bladder storage, emptying and coordinated urinary sphincter activity , are controlled by the sympathetic, parasympathetic, and somatic nervous systems. Parasympathetic nerves in the spinal cord (S2-S4) act to contract the bladder and relax the urethra through the release of acetylcholine, which excites smooth muscle muscarinic receptors (17). This causes urination through detrusor contraction. Postganglionic sympathetic neurons (T11- L2) . release noradrenaline causing bladder base contractions and relaxation of the bladder body, mediated by acetylcholine on nicotinic receptors. This encourages bladder storage through contraction of the urethral sphincter and relaxation of the detrusor muscle. Finally, somatic efferent motor neurons arising from the Onuf nucleus in the sacral spinal cord innervate the external urethral sphincter andact on nicotinic receptors using acetylcholine (17). The spino-bulbar-spinal micturition reflex is voluntarily inhibited by the pontine micturition center, primarily mediated by central dopamine, serotonin, noradrenaline, opioid and gamma amino butyric acid (GABA) pathways(17). The micturition reflex is dependent on sensory fibers from the bladder firing signals to the brain causing the urge to urinate. The pelvic afferent nerves that monitor bladder volume are small

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