Micturition and the soul

Abstract

There is a close connection between micturition and emotion. Several species use micturition to signal important messages as territorial demarcation and sexual attraction. For this reason, micturition is coordinated not in the spinal cord but in the brainstem, where it is closely connected with the limbic system. In cat, bladder afferents terminate in a cell group in the lateral dorsal horn and lateral part of the intermediate zone. Neurons in this cell group project to supraspinal levels, not to the thalamus but to the central periaqueductal gray (PAG). Neurons in the lateral PAG, not receiving direct sacral cord afferents, project to the pontine micturition center (PMC). The PMC projects directly to the parasympathetic bladder motoneurons and to sacral GABA-ergic and glycinergic premotor interneurons that inhibit motoneurons in Onuf's nucleus innervating the external striated bladder sphincter. Thus, PMC stimulation causes bladder contraction and bladder sphincter relaxation, i.e., complete micturition. Other than the PAG, only the preoptic area and a cell group in the caudal hypothalamus project directly to the PMC. The ventromedial upper medullary tegmentum also sends projections to the PMC, but they are diffuse and also involve structures that adjoin the PMC. Neuroimaging studies in humans suggest that the systems controlling micturition in cat and human are very similar. It seems that the many structures in the brain that are known to influence micturition use the PAG as relay to the PMC. This basic organization has to be kept in mind in the fight against overactive bladder (OAB) and urge-incontinence.

Cerebral control of the bladder in normal and urge-incontinent women

“…The hypothalamic region in Supplementary Table 6 and Figure 3 is identical to one responding to decreased urge to void in the same study; it appears to be the perifornical area of the hypothalamus, which in the cat has direct monosynaptic access to the PMC (Holstege, 2005). Strong activation at large bladder volumes in subjects with normal bladder control suggests an inhibitory influence on the PMC.…”

The supraspinal neural correlate of bladder cold sensation—An fMRI study

“…The PAG is an important relay station for sensations arising from visceral organs [Craig, 2002;Holstege, 2005] and therefore, a more robust activation of this region was expected. Failure to detect activation in the group analysis may be due to methodological limitations related to inadequate spatial and temporal resolution of both fMRI and PET, and also increased susceptibility to movement-related artifacts in the brainstem region.…”

70 Supraspinal control of urine storage and micturition in men – an fMRI study

“…This finding can be explained by the increased neuronal recruitment and cognitive effort necessary to initiate micturition. Voluntary control of micturition including its initiation usually requires 4 elements; 1) conscious bladder sensation, 2) assessment and integration of environmental, emotional, and social aspects, that is, it is safe, appropriate, and comfortable to micturate, 3) release of the bulbospinal micturition reflex, and 4) adequate sensorimotor function to relax the EUS and pelvic floor muscles (Holstege 2005;Fowler et al 2008;de Groat and Wickens 2013). In line with these notions, the supraspinal activity we observed included structures involved in 1) interoception, that is, the right anterior insula, PAG, ventral posterior thalamic nucleus (Craig 2002), 2) decision-making, social judgment, and emotional/motivational processing, that is, the IFG, MFG, and the cingulate cortex (Rolls and Grabenhorst 2008;Torta and Cauda 2011), 3) execution of the bulbospinal micturition reflex, that is, the pons (de Groat and Wickens 2013), and 4) sensorimotor control, that is, the precentral gyrus, OP, cingulate cortex, and cerebellum (Eickhoff et al 2010;Torta and Cauda 2011;Manto and Oulad Ben Taib 2013).…”