Figure 4. Central CLOCK synchronizes the peripheral CLOCKs and regulates peripheral organ activities via neural and humoral interactions. Light/dark information travels via the retinohypothalamic tract (RHT) from the retina – specifically from the retina ganglion cells which are intrinsically photosensitive – to the suprachiasmatic nucleus where efferent neurons 1) transfer timing information to other parts of the CNS such as th e paraventricular nucleus (PVN), medial preoptic area (MPO) and dorsomedial nucleus (DMH) of the hypothalamus and the pineal gland, and 2) affect the autonomic nervous system (sympathetic and parasympathetic) and regulate the secretion of pituitary hormones and melatonin, which in turn control basic functions of the body like sleep, food intake and body temperature. DMV: dorsal motor nucleus of vagus . ( Adapted from Nader, N, Chrousos, GP, Kino T. Trends Endocrinol Metab 2010;21:277).