The Circadian Rhythm and Sleep Cycle

CIrcadian Rhythm and Sleep Cycle
Sleep Hygeine

What is the Circadian Rhythm?

There is a 24-hour circadian rhythm that regulates our sleep cycle. Our hormones are at play with regards to when we feel drowsy and when we experience wakefulness. Regardless if an individual considers themselves a night owl, or they are shift workers, the human body, animals and plants, are all regulated by this internal circadian clock called “The Circadian Rhythm”.
The circadian rhythm influences us both when we are asleep and when we’re awake. Otherwise known as the sleep-wake cycle, or the sleep cycle, the release of specific hormones makes this all possible. One such hormone that gets secreted and peaks, particularly when we are in the deepest stage of sleep, is growth hormone. It is through this release that our brain and body repairs and restores itself for continued health and well-being.
When there is a disruption to the circadian rhythm, there are some consequences we soon experience, such as increased fat storage, depression, diabetes and/or bipolar disorder. When a person has not had adequate sleep for an extended period, their sleep cycle informs them that they need to have rest. The result is the feeling of drowsiness.
Sleep Time
The timing that is set for both sleep and wakefulness can differ during a 24-hour span. At 2 – 4am, most adults will find they are very sleepy. Interesting, it turns out that we are also driven to sleep between 1 – 3 pm. Those with sleeplessness, requiring an insomnia treatment, are those that will suffer the most at these times of the day. This reality is all thanks to our natural circadian rhythm.

Sleep Cycles and Brain Waves


  • The “Insight” brainwave
  • The fastest frequency of all brain waves
  • Linked to the high-level information processing


  • “Waking Consciousness”
  • Responsible for reasoning


  • Present mostly in deep relaxation.
  • When we are awake, alpha may slip us into a daydream
  • Alpha brainwaves help us with light meditation.
  • Alpha brain waves help focus us through the quiet balancing of the mind
  • Alpha brain waves are present when our intuitive facilities are optimised


  • Light meditation and sleeping brainwave.
  • It includes REM dream state.


  • Deep REM sleep brainwave
  • Realm of the unconscious mind
  • Linked to repair and regeneration
  • The reason it is called delta sleep is because of the presence of high-amplitude, low-frequency delta waves. These are witnessed in a patient’s EEG.
  • It is hard to wake a person once they are in deep sleep.
  • Human growth hormone has been shown to release in pulses during deep sleep.

The Stages of Sleep within our Sleep Cycle

When we are about to fall asleep, our brain will enter the Alpha and Theta waves. This is when we experience dreaminess. This same dreaminess that is encountered during the day does not typically result in sleep, but at night it will. This is due to our circadian cycle. Many people who practice the art of mediation will be able to gain control over their brain waves. Alpha is a very restful/peaceful state.
Once our brains begin to enter the Theta wave, we will feel slightly awake and easily roused, but still in a light state of sleep. If we have been undisturbed in this stage, within 5-7 minutes the 2nd stage of sleep will be reached.
Sleep Patterns
It is crucial to understand your sleep cycle. Through the optimisation of your sleep sanctuary, you move towards the improvement of cellular regeneration and repair. Our specialist has created a list of sleeping tips that will enable you to get the rest you need every night.


  • (2018). New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation. British journal of pharmacology, 175(16), 3190–3199. Advance online publication. doi:10.1111/bph.14116 
  • Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Stroke. (2018). Retrieved 8 November 2018, from Https://

  • Bellesi, M., Riedner, B. A., Garcia-Molina, G. N., Cirelli, C., & Tononi, G. (2014). Enhancement of sleep slow waves: underlying mechanisms and practical consequences. Frontiers in systems neuroscience, 8, 208. doi:10.3389/fnsys.2014.00208 

  • Nedeltcheva, A. V., Kilkus, J. M., Imperial, J., Schoeller, D. A., & Penev, P. D. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of internal medicine, 153(7), 435-41.

  • Beccuti, G., & Pannain, S. (2011). Sleep and obesity. Current opinion in clinical nutrition and metabolic care, 14(4), 402-12.

  • Institute of Medicine (US) Committee on Sleep Medicine and Research; Colten HR, Altevogt BM, editors. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington (DC): National Academies Press (US); 2006. 2, Sleep Physiology.

  • Tosini, G., Ferguson, I., & Tsubota, K. (2016). Effects of blue light on the circadian system and eye physiology. Molecular vision, 22, 61-72.

  • Bass, J., & Takahashi, J. S. (2010). Circadian integration of metabolism and energetics. Science (New York, N.Y.), 330(6009), 1349-54.

  • Mahowald MW. Sleep Deprivation: Basic Science, Physiology, and Behavior Sleep Deprivation: Clinical Issues, Pharmacology, and Sleep Loss Effects. Arch Neurol. 2005;62(8):1314. doi:10.1001/archneur.62.8.1314-a

You might also like