The Nervous System

Abstract

The mammalian circadian system comprises a master clock, located in the hypothalamic suprachiasmatic nucleus (SCN), and peripheral clocks situated throughout the body, including extra-SCN brain tissues. Individual cells have their own molecular circadian clock machinery, namely, transcriptional and translational feedback loops composed of several clock genes and their protein products. The SCN orchestrates peripheral clocks to carry out their physiological functions, meaning that the SCN does not merely drive the circadian signal but synchronizes the cell-based and peripheral clocks. The SCN itself is composed of multiple networks of oscillator cells in which both neurons and glia are involved. The hierarchical multi-oscillator system, both within the SCN and throughout the body, enables temporally coordinated functions, which are crucial for good health.