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Sleep Quality and Circadian Rhythm Regulation
🕑 Added 2025-07-23 18:39:57 +0000 UTC
Almost all life on earth uses an internal biological clock to anticipate the profound changes that result from the Earth's rotation upon its axis. In organisms as varied as photosynthetic bacteria and humans, physiology and behaviour are ‘fine-tuned’ to the varied, yet predictable, demands of the day/night cycle. Creatures effectively ‘know’ the time of day, and these internally generated daily cycles are called ‘circadian rhythms’, which comes from the Latin circa (about) and dies (day). In addition to the alignment of the internal and external day, a circadian clock also ensures that biological processes occur in the appropriate temporal sequence. For cells to function properly they need the right materials in the right place at the right time. Thousands of genes have to be switched on and off in a specific order. Proteins, enzymes, fats, carbohydrates, hormones, nucleic acids and other compounds have to be absorbed, broken down, metabolized and produced in a precise time window. Energy has to be obtained, and then partitioned across the cellular economy and allocated to growth, reproduction, metabolism, locomotion and cellular repair. Without this internal temporal compartmentalization, our biology would be profoundly compromised.
Circadian rhythms must also be synchronized or entrained to the external environment using signals that provide time of day information (zeitgebers), and the patterns of light produced by the Earth's 24 h rotation provide the dominant entrainment cue. However, in many species, other environmental zeitgebers such as temperature, food availability, rainfall and even predation can contribute to entrainment. The key point is that circadian rhythms are not driven by an external cycle but are generated internally, and then synchronized to the external 24 h world.
At the heart of the circadian system of mammals is a structure located deep within the brains hypothalamus called the ‘suprachiasmatic nuclei’ or SCN.
The SCN of humans comprises about 50 000 cellular circadian oscillators sufficiently stable to generate circadian rhythms of neuronal firing for at least six weeks in vitro. This was first shown in dispersed SCN neurons from neonatal rats, placed into the culture on a grid of microelectrodes. Individual neurons displayed robust circadian rhythms in electrical firing, but the phases of these individual rhythms were all different, showing that SCN neurons act as individual clocks and that the basic oscillation lay within individual cells, and was not the emergent property of a network of individual neurons.
Although the SCN is the ‘master clock’ in mammals, it is not the only clock . There are cellular clocks, using essentially the same subcellular mechanisms, within the liver, muscles, pancreas, adipose tissue and probably in every organ and tissue of the body. Destruction of the SCN abolishes multiple rhythms, such as locomotor activity, and this was the reason that the SCN was considered to ‘drive’ 24 h rhythmicity. However, it is now appreciated that the loss of overt rhythmicity occurs because (i) some of the individual peripheral clock cells dampen, and lose rhythmicity after several cycles; but more commonly, because (ii) the individual cellular clocks become uncoupled from each other. The cells continue to tick, but at different phases so that an overt 24 h rhythm within the tissue or organ is lost. This discovery led to the appreciation that the SCN acts as a pacemaker to coordinate, but not drive, the circadian activity of billions of individual peripheral circadian oscillators throughout the tissues and organs of the body. The signalling pathways used by the SCN to entrain these peripheral clocks are still uncertain, but we know that the SCN does not send out countless separate signals around the body targeted at specific individual clocks. Rather, there seems to be a limited number of neuronal and humoral signals. The SCN also receives feedback signals from the periphery that allows the whole body to function in synchrony with the varying demands of the 24 h light/dark cycle. The result is a complex circadian network that coordinates rhythmic physiology and behaviour.
inadequate sleep is suggested if some/all of the following are experienced:
- are dependent upon an alarm clock, or another person, to get you out of bed
-over sleep extensively (get up late) on free days
-take a long time to wake up and feel alert
-feel sleepy and irritable during the day
-feel you need a mid-afternoon nap to function adequately
-are unable to concentrate and exhibit overly impulsive behaviours
-crave caffeinated and sugar-rich drinks
-receive advice from family, friends, work colleagues that your behaviour has changed, specifically you are more irritable, lack empathy in social situations, and are less reflective (disinhibited) experience increased worry, anxiety, mood swings and depression
The idea behind this field is to regulate your circadian rhythm therefore improving your sleep quality (but there are also some concepts to improve your sleep quality in other ways).
The source of this text and base of this field can be found here: https://pmc.ncbi.nlm.nih.gov/articles/PMC7202392/
It's a really good study, I suggest having a look for the ones interested.
I suggest using it in the morning/evening, this is why the song isn't a calming one. 2 to 3 times is a good amount per session, 1 session a day is a good amount too.
This was a suggestion of a lot of members so I won't mention any specific names.
Comments
George C.
Thank You So Much, PU! 🙏 This will be a Great addition to my Playlists and Very Useful, since I still have sleepless nights quite often.
Mila
Thank you for making this. This is such an important issue for general health 💪🏽
