What is the body’s biological clock?

Sleep and the body’s biological clock: What is the body’s biological clock?

This mechanism functions as an organism’s intrinsic timing device. Specific proteins in the body interact with our cells to coordinate what’s known as the circadian rhythm; physical, mental, and behaviour changes that follow a daily cycle. Sleeping at night and being awake during daytime is an example of a light-driven circadian rhythm. Natural factors within the body produce circadian rhythms, but the external environment can also influence this biological system.

Do circadian rhythms affect body function and health?

Circadian rhythms influence sleep-wake cycles, hormones, eating and digestion, and body temperature. Body clocks that run fast or slow, become interrupted or abnormal have been linked to chronic health conditions such as sleep disorders, obesity, diabetes, and depression.

Sleep and the endocrine system

The endocrine system is a collection of glands that secret hormones into our blood stream and carry them to target organs to exert their functions. The secretion of certain hormones increases during sleep (e.g. growth hormone, prolactin) while others decrease during sleep (e.g. thyroid stimulating hormone and cortisol). There is evidence to show that a link exists between endocrine dysfunction and poor sleeping patterns.

The HPA (hypothalamic-pituitary-adrenal) axis is an important neuroendocrine response system to stress and is regulated by a diverse group of projections located in and/or around the brain, including the limbic system, mid-brain, and brain stem nuclei. The HPA axis ultimately controls levels of cortisol and other stress hormones released by the adrenal glands. The result of HPA activation is to increase cortisol levels in the body in times of high stress to facilitate the ‘fight or flight’ response. Normally, cortisol levels are meant to peak at early morning, and gradually decline throughout the day. Prolonged emotional and/or physical stress can negatively affect the HPA axis, leading to consistently high cortisol levels, disrupting sleep and reducing melatonin production in the body. Melatonin promotes sleep, but high cortisol levels disrupt the delicate balance.

Diabetes is a disease which negatively impacts the body’s production of insulin, a hormone that regulates blood sugar. Adults who report getting 5 or less hours of sleep per night were 2.5 times more likely to have diabetes, compared to those who slept the recommended 7-8 hours per night (National Sleep Foundation, 2018).

Bottom line: Chronic sleep deprivation can cause internal body mechanisms to go wonky. In our society, working overtime and long work weeks are signs of high achievers, people that ‘get ahead’. As it turns out, skipping on sleep doesn’t really help any of us get ahead-it makes us sick, depressed, and ages our bodies at an accelerated rate.

Here are some healthy sleep tips:

  • Stick to a sleep schedule of the same bedtime, and the same wake-up time, even on weekends.
  • Practice a relaxing bedtime routine by avoiding bright lights before bed, light stretching exercises, or engaging in a short pre-bedtime meditation session.
  • Include exercise as part of your daily routine, especially vigorous exercise 2-3 times per week. However, don’t exercise at the expense of your sleep!
  • Overhaul your sleeping quarters. Your bedroom should be cool (between 60-67 F), free from any noise that may disturb you, and free from any light. If needed, consider blackout curtains, an eye mask, white noise machines, and other devices to help design an ideal sleeping environment.
  • Sleep on a comfortable mattress and pillows. Most good quality mattresses have a life expectancy of 9-10 years. It should be supportive, not saggy in the middle! Make sure the material, including your bedsheets and pillows, are free of allergens, especially if you are prone to hay-fever. Changing your bedsheets every 10-14 days, and wash pillow cases every 2 days to avoid exposure to dust mites and other microscopic nasties.
  • Try aromatherapy. Essential oils such as lavender and bergamot, and ylang ylang rubbed on the inside of the wrist can help to relax your nervous system and promote a restful sleep.
  • Sip on some herbal teas. Some helpful sleepy teas include skullcap, passionflower, lavender, and fennel.
  • Avoid caffeine and alcohol in the evening.

Sleep plays an important role in your physical and mental health. The way you feel while you’re awake in part is dependent upon what happened while you were sleeping. During sleep, your body is working to support healthy brain function and restore physical wellbeing. In babies, young children, and teens, proper sleep also supports growth and development. Ongoing sleep deficiency can lead to long-term health conditions, also affecting how you think, feel, and interact with others. After several nights of losing sleep, even at a loss of just 1-2 hours per night, your body will function as if it has missed 1-2 full nights of sleep!

If you suspect you are suffering from a sleep-related condition or are concerned you might not be getting the quality sleep your body needs, contact Elevate on 9252 2225 and book in to see our GP who can refer you to our sleep specialists. We spend up to one-third of our lives sleeping, so time to make sure you are getting the health benefits of a proper night’s rest.


National Institute of General Medical Sciences. (November 2017). Circadian rhythms. Retrieved from https://www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx.

National Heart, Lung, and Blood Institute. (2018). Why is sleep so important? Retrieved from https://www.nhlbi.nih.gov/node/4605.

National Sleep Foundation (2018). Healthy sleep tips. Retrieved from http://www.sleepfoundation.org.

National Sleep Foundation (2018). The physiology of sleep-the endocrine system and sleep. Retrieved from http://sleepdisorders.sleepfoundation.org/chapter-1-normal-sleep/the-physiology-of-sleep-the-endocrine-system-sleep/.

Smith, J. How to wake up immediately in the morning. [Life Hack Blog]. Retrieved from http://www.lifehack.org.

The Sleep Advisor (2018). 48 sleep hacks: dramatically improve your sleep and energy [online e-book]. Retrieved from http://www.sleepadvisor.org.

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