Circadian rhythm & zeitgebers¶
The circadian rhythm is the roughly 24-hour internal cycle that regulates sleep, alertness, body temperature, and hormone release. It is generated by a master clock in the brain (the suprachiasmatic nucleus) and kept aligned to the day by external time cues.
Zeitgebers¶
A zeitgeber ("time-giver") is an external cue that entrains the circadian clock to the 24-hour day:
- Light — the most powerful zeitgeber, especially bright morning light.
- Meals — when you eat across the day.
- Activity — exercise and physical activity.
- Social routine — work, school, and contact with others.
In many circadian rhythm disorders the clock either runs at a period different from 24 hours, or fails to stay entrained to its zeitgebers.
Contributions welcome
This is a starter page. If you can clearly and accurately explain entrainment, the role of melatonin, or light timing, please improve it.