What is the Origin of Endogenous Rhythm Entrainment?

The term comes directly from chronobiology, combining endogenous (originating from within) and entrainment (from the French entraîner, to drag along or synchronize). The primary entraining signal is light, acting on the master clock in the brain. The concept explains why biological clocks remain accurate despite their intrinsic drift.

What is the Mechanism of Endogenous Rhythm Entrainment?

Light input to the retina stimulates the suprachiasmatic nucleus (SCN) via the retinohypothalamic tract, acting as the most potent zeitgeber. The SCN then adjusts the phase of its molecular clock, which in turn dictates the timing of melatonin and cortisol secretion, two critical endocrine markers of rhythm. This phase adjustment allows the entire system to shift and maintain coherence with the external 24-hour cycle.

Endogenous Rhythm Entrainment ∞ Area

Endogenous Rhythm Entrainment

Meaning

The synchronization of the body’s internal, self-sustaining biological rhythms (endogenous rhythms) to external environmental cues, known as zeitgebers. Entrainment is the process that keeps the body’s circadian clock aligned with the 24-hour day-night cycle, which is fundamental for coordinating hormone release, metabolism, and behavior. Proper entrainment is essential for preventing the metabolic and hormonal consequences of chronic circadian misalignment.