Organization of the neural switching circuitry underlying reflex micturition

Abstract

The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain and spinal cord that coordinates the activity of the bladder and urethral outlet. Experimental studies in animals indicate that urine storage is modulated by reflex mechanisms in the spinal cord, whereas voiding is mediated by a spinobulbospinal pathway passing through a coordination centre in the rostral brain stem. Many of the neural circuits controlling micturition exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. This study summarizes the anatomy and physiology of the spinal and supraspinal micturition switching circuitry and describes a computer model of these circuits that mimics the switching functions of the bladder and urethra at the onset of micturition.

A young man with herpes simplex encephalitis: Andrew and Nathan type urodynamic abnormality

“…The present case urodynamically showed decreased bladder sensation due mostly to left-side-dominant bilateral lesions at the middle cingulate and insular cortices [9]. It is well documented that bladder afferent signals reach the frontal lobe including the prefrontal, cingulate and insular cortices in experimental animals [10,11] and humans [12,13]. Therefore, it is reasonable to assume that lesions in the cingulate and insular cortices lead to decreased bladder sensation.…”

“…Therefore, it is reasonable to assume that lesions in the cingulate and insular cortices lead to decreased bladder sensation. DO is a motor phenomenon, and commonly occurs in lesions in the cingulate and insular cortices [14] that mainly inhibit the micturition reflex [11]. It is noteworthy that before the occurrence of DO, he was unable to contract his bladder, which was observed with decreased bladder sensation.…”

“…This combination of bladder disorder is previously not well documented. It is reasonable to assume that triggering/initiation of bladder contraction needs appropriate sensory input from the lower urinary tract [11]. It is documented that dorsal rhizotomy interrupted the micturition reflex [15] and lessens DO in patients with intractable urinary incontinence.…”

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).…”

“…The PMC, via one long, descending pathway to the sacral spinal cord, controls both the relaxation of the EUS and the contraction of the detrusor, although micturition in healthy humans relies on this reflex circuitry only during early infancy. During brain maturation and social education this reflex is gradually put under suprapontine control (de Groat 2002;de Groat and Wickens 2013).…”