Figure 1.

The mammalian circadian system: (a) The circadian rhythm generator in the suprachiasmatic nucleus (SCN) is entrained to light information conveyed to the brain from the retina via the retinohypothalamic tract (RHT). (b) The time information is then transmitted from the SCN to subsidiary circadian oscillators in the brain and the body via neuronal networks and hormones to regulate rhythmic brain and body functions [Reprinted with permission from ref. [2]. Copyright 2013 Springer Nature].