The steps
The master clock
A master clock in the brain, the suprachiasmatic nucleus, keeps your body's 24-hour rhythms in step. It controls melatonin based on how much light your eyes receive.
Source: National Institute of General Medical Sciences (NIH), Circadian rhythms
Light sets the time
Light has perhaps the greatest influence on your body clock, and light at night can lower the amount of melatonin you make.
Sources: National Institute of General Medical Sciences (NIH), Circadian rhythms; healthdirect Australia, Melatonin
The darkness signal
Melatonin is made by the pineal gland. Its levels rise when it is dark, about two hours before sleep, helping to get you ready for sleep.
The morning lift
Cortisol follows a daily pattern too, rising in the early morning and peaking at about 8 am.
When the clock slips
Jet lag and shift work alter the normal sleep-wake cycle. Long-term sleep loss and continually shifting rhythms can increase the risks of obesity, diabetes, mood disorders and heart and blood pressure problems.
Source: National Institute of General Medical Sciences (NIH), Circadian rhythms
Keeping time
Going to bed and waking up at around the same time each day, keeping the bedroom dark and quiet, and avoiding screens in bed all help.
Source: healthdirect Australia, Sleep
Quiz
1. What has perhaps the greatest influence on your body clock?
Answer: Light. Light has perhaps the greatest influence on circadian rhythms, according to the US National Institute of General Medical Sciences.
Source: National Institute of General Medical Sciences (NIH), Circadian rhythms
2. When do cortisol levels naturally peak?
Answer: In the early morning, at about 8 am. Cortisol levels rise in the early morning and peak at about 8 am.
3. When do melatonin levels rise?
Answer: When it is dark. Melatonin levels increase when it is dark, rising about two hours before sleep.