What Is Your Circadian Cycle?

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Rhythms of the body

There are very few things in nature that are linear, everything moves in circles of changing and adapting life patterns. As humans we have natural body and brain cycles that run over a 24 hour period.

These cycles or rhythms control many body functions switching them on or off at the most appropriate times. For example the circadian rhythms are responsible for or have an influence over:

  • Feeling hungry
  • Body temperature
  • Sleep-wake-sleep patterns
  • Hormone production
  • Cell regeneration

These rhythms are found not just in humans but in other animals, plants,fungi and even some bacteria. Scientists have found that these rhythms are *endogenously generated, but there are environmental factors that also have an influence - such as how much day light there is and seasonal temperatures.

*Endogenously means that the body produces these rhythms from within.

Biological Clocks.

Within the cells of our body, there are certain molecules that are responsible for driving the circadian cycles. They are in turn controlled by one master biological clock that is found in the brain. The hypothalamus has an area within it called the SCN (suprachiasmatic nucleus). There are about 20,000 nerve cells within the SCN and lying just above our optic nerve in the eye. This proximity to the the nerve of vision is able to relate immediate information on how light or dark the environment is. In addition, our personal circadian rhythms are determined genetically by how our mother and father's cycles operate.

One of the main functions of the circadian cycle is to regulate our sleep-awake-sleep patterns. So much so that any interruption of the rhythm can have unpleasant side effects - this is why we experience jet lag. However, many people also suffer from sleep disorders that are thought to be wholly or partially influenced by factors affecting the circadian cycle.

Circadian cycle and sleep

The body's master biological clock that we mentioned earlier - SCN (suprachiasmic nucleus) controls the release of a substance called melatonin. Melatonin is a hormone secreted by the pineal gland in the brain - and it's this hormone that makes you feel sleepy at night time. Medical researchers have found that as we get older, less melatonin is released. This is probably one reason young people usually don't have any problems sleeping as they will have higher amounts of melatonin secreted.

Babies don't have a functional circadian cycle until about 12-16 weeks - this is why they can seem to turn night into day. New born babies for example don't develop their light-dark cycles until about 6 weeks old. However, even at 12-16 weeks, babies are still developing their rhythms - they will only slowly mature into longer sleeping patterns at night.


Jet lag

In the case of jet leg what happens here is that although you travel through different time zones, your circadian cycle is set to your home environment. Your watch might say 9am, but your circadian rhythms are still in a home cycle where it might be 9pm. Eventually your circadian rhythms will come back into tune but it can take a few days. How severe you experience jet lag normally depends on how many time zones you cross and the distance travelled. The main symptoms are:

  • Sleep disturbance - this is one of the most common problems and in severe cases people can find themselves wide awake at night while feeling very tired during the day.
  • Confusion
  • Headaches
  • Lack of concentration, poor memory.
  • Gastric upsets - diarrhoea, nausea, loss of appetite etc.
  • Anxiety
  • Disorientation, feeling light-headed
  • Irregular periods can occur in women who travel frequently.
  • Movements are clumsy, un-coordinated.
  • General ill feeling, muscle pain and sweating.


However the circadian cycle can cause more than jet lag. Sleep disorders as well as obesity and diabetes have all been linked to problems with these body rhythms.

Babies don't have a fully functional circadian rhythm until between 12 and 16 weeks.
Babies don't have a fully functional circadian rhythm until between 12 and 16 weeks. | Source
The optic nerve sends information about the amount of light or dark in the environment and this is a major factor in regulating the circadian cycles.
The optic nerve sends information about the amount of light or dark in the environment and this is a major factor in regulating the circadian cycles. | Source

Have you ever suffered from sleep problems?

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When the rhythm goes wrong?

To finish off we'll have a brief look at what happens when the circadian cycle goes wrong - and possibly leading to problems such as sleep disorders.


One of the most common sleep disorders is Circadian Rhythm Insomnia. This is where the person's natural rhythm of 'dark-sleep, light-awake' is disrupted for some reason. The most common causes for this disruption are:

  • Jet lag - usually this will correct itself unless you are someone who constantly travels through different time zones.
  • Shift work - people who rotate shifts can have sleep problems and also those who work constant/frequent night shifts.
  • Advanced or delayed sleep phase syndrome - these conditions involve people becoming tired and then alert at inappropriate hours of the day and night.
  • Non 24-hour sleep/wake disorder - this involves periods of insomnia that tend to occur at different times each night. People may wake up late in the morning for example and fall asleep later at night. They will also experience periods of falling asleep perhaps in the evening and waking up in the early hours of the morning.

The treatment for circadian sleep disorders depends on the particular sleep problem affecting the person. Once this is established a number of therapies can be used to try and get the person back into normal rhythms. For example some treatments might involve:

  • Cognitive therapy
  • Relaxation
  • Self-hypnosis
  • Bright light therapy
  • Chronotherapy - this is where bedtime is slowly adjusted until the desired time for sleeping and waking is reached.

For many people a combination of techniques is often required rather than just one.

Lastly, if you do have problems with your sleep patterns, then speak to your doctor. Disturbed sleep doesn't just result in loss of a few hours rest that you can make up at some other time. Without regular, refreshing sleep, people can develop numerous physical and mental health conditions.

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Comments 22 comments

innerspin profile image

innerspin 3 years ago from uk

Very interesting hub. Most of the people I work with have to do night shifts part of the time, some find it very disruptive and feel " jet lagged." Don't think I could do it! Disruption of the Circadian cycle can be stressful.


torrilynn profile image

torrilynn 3 years ago

seeker7, thanks for this outlook and i never knew exactly what circadian cycles were until i came across your hub. thanks again. voted up.


Bumpsysmum profile image

Bumpsysmum 3 years ago from Cambridgeshire

Great Hub Seeker7. I have found as I've got older that my sleep patterns have changed drastically. I used to have no problem sleeping, as a teenager I would joke that I could sleep pegged to a clothes line. Now I tend to have no trouble getting to sleep but wake after an hour or two then can't get back to sleep for ages. I have tried all sorts of medication and also retraining myself, but I think I'm at that age as you say where I need less sleep anyway. I do find that if I have a 'good' night and sleep right through I actually feel worse than if I'd been awake half the night! I don't seem to suffer though. Voted up, useful and interesting.


Ghaelach 3 years ago

Hi Helen.

A very interesting and informative article you have written and researched.

The part about sleep disorder interested me as I am on the boarder line with Apnea. Which is abnormal pauses in breathing and this can last from at least ten seconds to minutes.

A good hub and good reading.

LOL Ghaelach


onegreenparachute profile image

onegreenparachute 3 years ago from Greenwood, B.C., Canada

Very interesting Seeker. I have always perferred the night. I like to go to bed around 1:00 - 2:00 and get up around 8:00 - 9:00. It just feels right and it came in mighty handy when I worked as a bartender.

I'm sharing this one! Thanks.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi innerspin, many thanks for stopping by and taking the time to leave a comment. I can sympathise with the folks you work with, I used to do permanent nightshifts in hospitals and yes 'jet-lagged' is the exact word I would use. When I finally came back to working regular day shifts I couldn't believe how much better I felt. Nightshift can take a lot out of you without even realising it.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi torrilynn, many thanks for stopping by and for taking the time to leave a comment - really appreciated! I know what you mean about the C.Cycles, they're mentioned and banded about a lot without really giving folks an explanation of what they are exactly, so hopefully the hub will continue to help people out with this.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Bumpsysmum, always lovely to hear from you and glad that you enjoyed the hub!

Yes, I'm very similar to you with sleep patterns. I'm 51 and getting the dreaded flushings etc. and they reckon that being pre-menopausal can affect your sleep, so that is certainly my problem at the moment. My big thing is trying to get over to sleep some nights and I can wake up then every two hours or so. Thankfully this isn't everynight but I rarerly go all night long anyway without waking at least once or twice. And yes, you can feel worse if you sleep all night - I find I'm really groggy and can also get tension headaches probably because of sleeping in the one position too long.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Ghaelach, many thanks for stopping by and glad that you enjoyed the hub.

Yes, Apnea, that is an interesting condition in itself and seems to affect quite a number of people and depending on how often they are woken up from sleep can be very stressful and debilatating.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi onegreenparachute (I love your nickname!!!),

Glad that you enjoyed the hub and many thanks for the interesting comment as well. The sleep pattern that you have obviously keeps you healthy and happy and that's all that matters. Everyone shouldn't be constrained by rigid bed time and rigid getting up times, everyone is different and like you, should go with the rhythm that suits them best.

My best times are evening/night and early morning. Late afternoons are a wash out for me, so unless vital, I just don't do afternoons! LOL!!


Rosemay50 profile image

Rosemay50 3 years ago from Hawkes Bay - NewZealand

This is a really interesting hub Helen, got me thinking about all sorts of things, like are the SCN messages affected by the loss of sight,

So many factors change our sleep pattern. I am one of those who is awake as soon as the sun shines through the blinds no matter how late I go to bed, so I find winters I wake much later.

I once did night shifts for six months and had to give it up, I was sleeping 12 hours a day and it still wasn't enough, and 'life' just didn't exist.

Hate jet lag because 2 or 3 days of the vacation are waste in recovering.

Anyways a super interesting and informative article Voting Up and sharing


Gypsy Rose Lee profile image

Gypsy Rose Lee 3 years ago from Riga, Latvia

Thanks for sharing this very informative and interesting hub. Never knew about these cycles. Now I will follow my sleep patterns more closely. Passing this on.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Rosemay, now that's a really interesting question about the SCN and loss of sight. I would think that people who gradually loose their sight would develop problems but those people born blind I wonder if they would generally adapt to this? Also I think even although blind, that some light would still get in through the eye and it would then depend on how or where the damage to the optic nerve was.

Yes, the dreaded nightshifts!!! I did permanent nights for three years and a break then for another four years and when I had finished the second lot I vowed never to do nights again and I never have! I think you don't really realise just how badly it does affect you until you start doing normal working hours again. Not just sleep is affected, although this is the worst of it, but eating habits and everything thing else that is suppose to function naturally doesn't!! I think nightshifts are like having jet lag on a permanent basis!!!


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Rasma, great as always to hear from you and glad that you enjoyed the hub - as always thanks for the support and the share, greatly appreciated!!


Joy.joy.joy profile image

Joy.joy.joy 3 years ago from Phoenixville, PA

Thanks! - great simple, accessible info. I am also interested in the tie-in between circadian sleep rhythms and the liver.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Joy-joy-joy - what a great, fun name you have - I love this!!!

Glad that you enjoyed the hub and I also find your interest with circadian rhythms and the liver very interesting. As far as I know the liver has it's own rhythm and when this is disrupted it can lead to metabolic diseases such as diabetes but also obesity and high cholesterol - definately a subject worth a hub in it's own right! Why not have a go!!


kashmir56 profile image

kashmir56 3 years ago from Massachusetts

Hi Helen great well written article with great interesting information, and much of it i did not know before. Thanks for helping me learn more about this subject with this great informative article. Well done !

Vote up and more !!! Sharing !


Eiddwen profile image

Eiddwen 3 years ago from Wales

So very interesting indeed seeker7 ; have a wonderful day and here's to many many more.

Eddy.


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Tom, always lovely to hear from you and glad you enjoyed the hub. There was a lot that was knew to me as well, so I guess we've both learned something new!


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Eddy, lovely to hear from you as always, and glad that you enjoyed the hub!


Alastar Packer profile image

Alastar Packer 3 years ago from North Carolina

Yes those were the good old days when sleep and its cycles weren't a problem. I just understand this waking up every two hours. Sure, there are some meds that tamper down those sleep interruptions but who wants to be on them forever? Besides you've got the tolerance factor. Anyway Helen, .learned some new things here. You heard that REM song called Daysleeper where he sings about Circadian Rhythms. And thanks for the thanks my friend, we'll see with the interview, and absolutely! Queen of the paranormal was a compliment by the person and I agree with them 100%!


Seeker7 profile image

Seeker7 3 years ago from Fife, Scotland Author

Hi Alastar, LOL!! Well I've been called a 'witch' at one time so I guess for most people 'Queen' is a step up!

As to sleeping, yes I remember very well being able to sleep at any time, anywhere! After the student parties it was amazing where you would doss down for the night and wake up ready to take on another day. Now, I'm like your good self, every two hours seeing the clock. I think the medication is okay for short periods, especially if people have severe insomnia, going through trauma, bereavement etc. But it's so easy to get into the habit of feeling that you must have the pills or sleep is impossible, that I personally don't think they're worth the risk. Folks should try some of the old remedies like rum & honey mede or a whisky 'hot toddie' - great things that taste lovely, non addictive and wonderfully relaxing. I've also heard, within reason of course, that they do have health benefits!

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