FIGURE 6.

Neuronal control of the lower urinary tract (LUT). The lower urinary tract receives neuronal control from both branches of the autonomic nervous system and the somatic nervous system. Sympathetic control arises from sympathetic preganglionic neurons in thoracic segments 11 to lumbar segment 2 that extend axons out the hypogastric nerve and synapse onto sympathetic postganglionic neurons within the inferior mesenteric ganglion. These sympathetic postganglionic neurons innervate the bladder, IUS, and urethra. Parasympathetic preganglionic neurons in sacral spinal cord segments 2–4 project axons out of the cord via the pelvic nerve and synapse onto parasympathetic postganglionic neurons within the pelvic ganglion. These postganglionic neurons directly innervate the bladder, IUS, and urethra. Interestingly, the external urethral sphincter is the only muscle in the LUT that is controlled via the somatic nervous system. This allows for voluntary control over urinary functions. (Created using www.biorender.com).