Nervous System

Sleep and Dreams

What are circadian rhythms?

Circadian (from the Latin circa, meaning “about,” and dies, meaning “day”) are the regular, internal body rhythms. Although our lives revolve around a 24-hour day, researchers have found that normal circadian rhythms are more on a 25-hour cycle. Many physiological processes, including the sleep/wake cycle, body temperature, gastric secretion, and kidney function, follow a set pattern. For example, body temperature peaks in the late afternoon/early evening and is lowest between 2:00 A.M. and 5:00 A.M. Blood pressure, heartbeat, and respiration follow rhythmical cycles. The production of urine drops at night, allowing for uninterrupted rest.

Circadian rhythm disturbances occur when sleep/wake cycles are interrupted. They often affect shift workers whose biological clocks are disrupted by conflicting sleep and work schedules. “Jet lag” is another form of circadian rhythm disturbance.


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