Body and brain internal clocks that control daily rhythms in mammals

The circadian system in mammals consists of a hierarchical structure of oscillators that operate at cellular, tissue, and systems levels.

• A shared molecular mechanism governs the cell-autonomous circadian oscillator present throughout the body.
• In the suprachiasmatic nucleus (SCN) of the hypothalamus, a network of neuronal oscillators functions as a master pacemaker.
• The SCN pacemaker drives rhythms in various physiological processes, including activity, rest, feeding, body temperature, and hormone levels.
• Coupling among SCN neurons enhances the robustness of the pacemaker, contributing to the stability of the organism's overall timing system.
• Cell-autonomous circadian clocks in most body cells are closely integrated with metabolic pathways.
• Circadian clocks may play a crucial role in regulating metabolism.

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