What is the Origin of Human Biological Clock?

The concept is an anthropocentric extension of chronobiology, the study of biological rhythms, which has been observed in organisms across all kingdoms of life. The clinical focus on the human clock became critical with the identification of the SCN as the central pacemaker and the discovery of the molecular clockwork involving core clock genes in the 1990s. This understanding highlights the vulnerability of human health to temporal misalignment.

What is the Mechanism of Human Biological Clock?

The central clock in the SCN receives direct light input from the retina via the retinohypothalamic tract, acting as the primary zeitgeber for entrainment. This light signal modulates the transcription-translation feedback loops of the core clock genes. The SCN then sends signals, both neural and hormonal, to peripheral clocks in organs like the liver and adrenals, ensuring the synchronized, rhythmic expression of metabolic and endocrine genes throughout the body.

Human Biological Clock ∞ Area

Human Biological Clock

Meaning

The intrinsic, genetically encoded time-keeping system present in virtually every cell of the human body, centrally regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus. This master clock synchronizes the 24-hour cycle of physiological processes, including sleep-wake cycles, core body temperature fluctuations, and the rhythmic secretion of nearly all endocrine factors. It is the fundamental mechanism that establishes the temporal order of human biology.