# Circadian Rhythm --- The **circadian rhythm** is a [[biology|natural]], internal process that cycles roughly ever 24 hours. It influences many biological factors in the body such as the [[sleep]]-wake cycle, and our moods. Not just humans have circadian rhythms—it's been observed in other animals, plants, fungi, and even cyanobacteria. Although it is largely internal, it is triggered, or regulated by outside factors called **zeitgebers** (German for "time givers"), like the rising or setting of the sun. A lot is affected by the circadian rhythm, such as (but not limited to) [[melatonin]] production, [[body temperature]], [[blood pressure]] and alertness. ![[circadian rhythm.png]] ## Circadian Rhythm Disorders **Circadian rhythm disorders**, or **sleep-wake cycle disorders** are problems that occur when your own circadian rhythm is out of sync with your environment. They are caused when people regular interruptions to their sleep patterns. For example, it's common to see this in night shift workers or people who experience jet lag often. It can also occur in people who change their bed time or wake up time regularly, have poor [[sleep|sleep hygiene]], people who have brain damage, or take certain drugs. [[older adult|Old age]] is also a risk factor. General signs and symptoms of circadian rhythm disorders include: - [[insomnia]] - excessive sleepiness. - difficulty waking - [[depression]] ### Delayed Sleep Phase Disorder Going to bed or waking up more than two hours later than what is considered "normal". **Advanced Sleep Phase Disorder:** If you have this sleep disorder, you fall asleep in the early evening (6 p.m. to 9 p.m.) and wake up in the early morning (2 a.m. to 5 a.m.). (Sounds like some discrimination against "night owls" if you ask me.) ### Jet Lag **Jet lag** is caused when the circadian rhythm has been disturbed from air travel to a destination that is two or more time zones different from where you departed. Eastward travel is more difficult than westward travel because it is easier to delay sleep than to advance sleep. ### Shift Work Disorder **Shift work disorder** comes from frequently rotating shifts or working the night shift. ___