Wize University Psychology Textbook > Consciousness
Circadian Rhythms
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Circadian Rhythms
Circadian Rhythms - biological cycles that include our sleep/wake cycle, digestive system, body temperature, blood pressure and blood sugar. Most run on an approximately 24 hour cycle.
The sleep/wake cycle is highly influenced by exposure to light and dark.
Changes in light and dark trigger the release of melatonin - a hormone that signals the onset of sleep. In an environment with unchanging light (always light or always dark), the sleep/wake cycle lengthens to approximately 25 hours.
Jet lag is the result of the difference between your biological clock and the time of day - your body needs some time to adjust your sleep and wake times. Generally, jet lag is worse when travelling east because it is harder to advance the biological clock (i.e., go to bed when you aren't sleepy) than to push it back (i.e., stay up a little longer even though you're sleepy).
Practice: Circadian Rhythms
Without changes in light and dark, the human sleep cycle: