Figure 2: Targets of the SCN. The temporal signal transmitted by the suprachiasmatic nucleus, the biological clock, is translated into a rhythmic hormonal pattern or signals provided by the autonomic system. This relationship provides information to the body that adjusts peripheral organs to the light-dark cycle. The bottom panel shows the circadian rhythm in blood levels of corticosterone, luteinizing hormone, and melatonin for rodents modified from [2].