Fig. 2.

Reflexes controlling storage of urine and micturition with an emphasis on physiological effects on the detrusor and external urethral sphincter. Reflexes are numbered for reference (as referred to in the text) and a suffix is added if the reflex mediates different responses during storage (s) or micturition (m). Reflexes that generate contractions are labeled with “+” on the target muscle, or “-” for relaxation of the muscle. Each reflex is labeled at the junction connecting afferent signals and efferent commands. Junctions are colored according to the afferent signals required for their activation (pudendal, pelvic, or both) and the “H” or “L” indicates that the corresponding sensory activity must be high or low, respectively. Reflexes that are abolished by high-level spinal cord transection are shown passing through supraspinal centers (SSC). a) Bladder distention evokes bladder contraction, which is silenced by spinal transection but persists after pudendal and hypogastric nerve transections: cat (Barrington, 1914). b) Passing fluid through the urethra with volume in the bladder evokes bladder contraction, which is reduced by spinal transection: cat (Barrington, 1914). c) Peng et al. 2008: Interventions reducing urethral afferent output decreases bladder contraction magnitude and voiding efficiency: rat (Peng, Chen, Chang, de Groat, & Cheng, 2006). d) Electrical stimulation of distal sensory branches of the pudendal nerve evoked reflex detrusor contractions at high bladder volumes, some of which were abolished by spinal transection: cat (Yoo et al., 2008a). e) Volume dependence of pudendal mediated supraspinal reflex contraction of detrusor: cat (McGee & Grill, 2014). f) Electrical stimulation of pudendal afferents evokes detrusor contractions at high bladder volumes and persists following hypogastric transection: cat (Woock et al., 2011). g) Electrical stimulation of pudendal nerve reflexively evokes detrusor contractions, and persists following spinal transection: rat (Chen et al., 2011). h) Electrical stimulation of pudendal afferents produce detrusor contraction only when intravesical pressure is high: cat (Bradley & Teague, 1972). i) Low frequency electrical stimulation of pudendal afferents inhibit detrusor contraction, an effect that persists following hypogastric transection and is abolished by local pharmacological blockade in the sacral cord: cat (McGee et al., 2014). j) Passing fluid through the urethra evokes external urethral sphincter relaxation, which persists following hypogastric and pelvic nerve transections: cat (Barrington, 1931). k) Electrical stimulation of proximal transected pudendal afferents evokes contralateral pudendal efferent activation at low frequency, an effect which can be inhibited with pelvic shock conditioning: cat (Bradley & Teague, 1972). l) Low frequency electrical stimulation of pelvic afferents activates the urethral sphincter, and persists following high-level spinal transection, suggesting a continence reflex at low pelvic afferent outflow: cat (Karicheti et al., 2010). m) Electrical stimulation of pelvic afferents readily induces a urethral sphincter contraction, and persists following spinal transection: cat (Bradley & Teague, 1972). n) Substantial bladder distention evokes urethral relaxation: cat (Barrington, 1914). o) High frequency electrical stimulation of pelvic afferents inhibits urethral sphincter activation, and persists following spinal transection: cat (Karicheti et al., 2010). p) Following recovery from spinal transection and hypogastric and/or pudendal nerve transection, leak point bladder pressure is increased by transecting the pelvic nerve, indicating that there is an internal pelvic spinal pathway promoting micturition: cat (Barrington, 1931). q) Following spinal transection bladder distention evoked detrusor contractions re-emerge in chronic conditions that can be abolished by capsaicin, which is known to block selectively unmyelinated afferent fibers carrying information about noxious bladder stimuli: cat (de Groat et al., 1990). r) High frequency electrical stimulation of pelvic afferents inhibits this hypogastric efferent reflex, thereby promoting detrusor contraction, and persists following spinal transection, whereas low frequency stimulation activates hypogastric efferents: cat (Karicheti et al., 2010). s) Onset, but not persistence, of spontaneous bladder contractions under isovolumentric conditions evoke a hypogastric efferent response that persists following spinal transection: cat (de Groat & Lalley, 1972).