CIRCADIAN RHYTHM

WHAT IS IT?

• Chronobiology
• Physical, mental, and behavioral changes in a 24 hour cycle. It is mostly in response to the light and darkness changes in an organisms environment.
• They influence sleep-wake cycles, hormones release, body temperature, and other functions within the body.
• It is produced naturally in the body, but is influenced by environmental factors.

SYSTEMS

• Sleep patterns are regulated by two body systems: sleep/wake homeostasis and the circadian biological clock.
• The sleep-wake system tells the body when it has been awake too long and it is time to sleep. Creates a balance of sleep and wakefulness.
• The circadian biological clock regulates the timing of sleepiness and wakefulness throughout the day. The dips are more or less intense based on the amount of sleep the person has gotten.

HOW IT AFFECTS TEENS

• During adolescence, there is a shift in the circadian rhythm which makes teens more alert and awake later in the evening. This makes it difficult for most teens to fall asleep before 11 pm. Because of the early school schedules that most teens must follow, their sleeping cycles get thrown off.
• Our "dips" occur between 2:00-5:00 pm, and 3:00-7:00 am. If sleep deprived, this phase of the cycle can stretch as far as 10:00 am.

HOW THE CYCLE IS CONTROLLED

• The circadian biological clock is controlled by a part of the brain called Suprachiasmatic nucleus (SCN). It is a group of hypothalamus cells that respond to light and dark signals. Light travels through the eyes and to the SCN, signaling the internal clock to be awake.
• SCN sends signals to regulate body temperature and hormone release, such as cortisol.
• Abnormal circadian rhythms have been linked to insomnia, obesity, depression, bipolar disorder, and seasonal affective disorder.

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MELATONIN

• SCN responds to light by delaying the release of melatonin. It is associated with sleep onset.
• It is produced when SCN signals the body when it is dark.
• Melatonin levels rise in the evening and stay risen throughout the night, promoting sleep.
• In teens, melatonin levels naturally rise later at night. Ways to help this is to keep lights dim at night, and get into bright light soon after waking up.

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JET LAG

• Jet lag offsets our natural sleep patterns. The brain is forced to shift its time and light cues, thus throwing the sleep cycle off course.
• With jet lag (and also in regular life with lack of sleep or irregular sleep patterns), people have symptoms such as feeling poorly and not being able to function and perform well.

CITATIONS:

• Sleepfoundation.org "sleep drive and your body clock"
• Nigms.nih.gov "circadian rhythms fact sheet" November 2012.