Page 13 - Bladder Dysfunction in the Context of the Bladder-Brain Connection - Ilse Groenendijk.pdf

Introduction 11
1.1 THE URINARY TRACT
The urinary tract manages the transportation and storage of urine and consist of the upper urinary tract and the lower urinary tract (LUT). The upper urinary tract includes the kidneys and the ureters. The LUT consists of the urinary bladder, the urethra, the external and internal urinary sphincters and the pelvic floor muscles; its anatomy differs between men and women. Although the ability to void at a socially appropriate place and time does not seem like a complex task for human being, it requires the proper functionality of many different complex pathways within the body. Disorders of the LUT (functional bladder disorders) create symptoms of the LUT. This thesis aims to improve our knowledge on diagnostics and treatment of such disorders and symptoms in the context of the bladder-brain connections.
The micturition-cycle is divided into the storage phase and the voiding phase. Dur- ing the storage phase the detrusor muscle in the bladder wall is relaxed, creating a low-pressure bladder without feeling the urge to void. If the amount of urine exceeds a certain threshold, an urge to void is felt. The voiding phase may start if we are in an appropriate place to void. During the voiding phase the external urethral sphincter relaxes, the detrusor muscle contracts, and the bladder empties. When voiding stops, the storage phase starts again.
1.2 INNERVATION OF THE LUT
The ascending and descending innervation of the LUT is warranted by three nerves (fig 1). Visceral information from the bladder, bladder neck and urethra, is sent to the pons and higher brain areas via both the hypogastric nerve (sympathetic) and the pelvic nerve (parasympathetic). These nerves are furthermore responsible for the descending auto- nomic innervation of the bladder. The somatosensory control and the motor control of the external urethral sphincter and genitalia are regulated through the pudendal nerve.1 The areas in the brain and brainstem involved in somatic and autonomic control of the LUT differ as to the specific task of the LUT. The precise working mechanism of these structures in the control of the LUT has not yet been completely clarified. The knowledge in this field is increasing rapidly, however, partly due to the evolution of dynamic brain imaging. Dynamic brain imaging captures the location of activation or deactivation in the brain over time during a specific task. The central innervation of the LUT in healthy subjects has been investigated using dynamic brain imaging but literature is still scarce. Furthermore, these techniques are prone to artefacts, and interpretation of the results is complicated. When focusing on LUT control, some brain areas are specifically studied. The cortex of the brain includes the primary motor cortex and the primary sensory
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