(a) The peripheral signals from the visceral organs (such as ghrelin and GLP1 from the gastrointestinal tract, insulin from the pancreas and leptin from the adipose tissue shown here or other metabolites and regulators discussed in section 3.2.2) reach two key regions of the brain: the MBH via pituitary-portal circulation, and/or the DVC constituting the AP and NTS via the circulation or through the sensory vagus nerve. (b) Schematic representation of the transport of blood-borne molecules to the MBH via the fenestrated capillaries of the ME. Tanycytes at the floor of the third ventricle (ME tanycytes) adapt their plasticity to permit the passage of molecules. Tanycytes at the ARH and VMH sense the uptake of peripheral signals and transmit them to the neighbouring neurons. Astrocytes at the interface of BBB capillaries also sense and transmit the systemic metabolic information to neurons. MCH neuronal projections from the LHA release MCH at the base or the pole of ependymal cells controlling ciliary beat frequency. AP, area postrema; ARH, arcuate nucleus of the hypothalamus; BBB, blood-brain barrier; CVO, circumventricular organ; DVC, dorsal vagus complex; LHA, lateral hypothalamic area; MBH, mediobasal hypothalamus; MCH, melanin-concentrating hormone; ME, median eminence; NTS, nucleus of the solitary tract; VMH, ventromedial nucleus of the hypothalamus.