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Presenter: Lena Edwards, MD

The human Circadian Clock is the endogenous biochemical mechanism that allows the body to anticipate and prepare for daily environmental changes thus contributing to the timely coordination of physiological processes. This master time keeper oscillates over a period of approximately 24 hours and is the central driving force of circadian rhythms. Although light is the most impactful exogenous influence, other factors such as stress and food intake can affect the function of the Circadian Clock.

The Circadian Clock is comprised of two primary components: 1) The Central Master Clock which is the central pacemaker located in the suprachiasmatic nucleus (SCN) within the hypothalamus; and 2) The peripheral ‘local’ clocks located in virtually every organ throughout the body. The Central Clock controls the activity of the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS). In turn, the HPA axis adjusts circadian rhythmicity of the peripheral clocks via the glucocorticoid receptor. Although the peripheral clocks are synchronized to the Central Clock, animal studies have shown that local peripheral clocks can operate even when uncoupled from the Master Clock. However, uncoupling of these two clock systems can cause significant metabolic dysregulation resulting in the development of diseases including obesity, metabolic syndrome, cardiovascular disease, and immune system dysfunction (i.e. autoimmunity, infections).

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