Figure 3.

Schematic summary of the higher-order projections to Onuf’s nucleus. Onuf’s nucleus (ON) receives direct projections from the paraventricular hypothalamic nucleus (Pa; in blue). The periaqueductal gray (PAG) in the mesencephalon controls the pelvic floor by stimulating the pelvic organ stimulating center (POSC; in red), which in turn projects to inhibitory interneurons in the sacral cord that finally innervate Onuf’s nucleus. Moreover, PAG sends efferent fibers to the nucleus retroambiguus (NRA; in green) in the medulla, which is then connected with Onuf’s MNs, which innervate the muscles determining the abdominal pressure. The strongest afferents to the PAG originate from different brain areas (identified in purple), such as the medial orbitofrontal cortex (OFC), the anterior cingulate gyrus (Cg), the preoptic area and hypothalamus (POA, Hyp), the lateral Bed Nucleus of Stria Terminalis (BNST) and the Central Nucleus of the Amygdala (CeA). Finally, projections from the limbic system and prefrontal cortex reach the PAG that then projects to the pelvic floor stimulating center (PFSC; in yellow) in the pons, which in turn innervates Onuf’s MNs.