Circadian Rhythms & Sleep/Wake Cycle | The CLOCK Inside YOU

how would you feel about spending 2 months alone in a cave in the French Alps that's months without seeing sunlight what do you think would happen to your brain and what do you think would happen to your sleep hey everyone welcome back to Bear it in mind in this video we're going to begin to explore biological rhythms as part of the bioc psychology topic biological rhythms are repeated patterns of changes in the body that are regulated by an internal clock in other words there are processes in your body that happen again and again that are controlled by a clock inside you there are three biological rhythms that we're going to explore in the next two videos Cadian ultradian and infradian in this video we will explore the Cadian Rhythm including the effect of endogenous pacemakers and exogenous zeit givers at the end of the video there'll be some practice questions of what we cover so that you can check your understanding and link below is a free resource that goes with this [Music] video circadian rhythms last for around 24 hours the word cira is Latin for about and DM is Latin for day so it means about a day an example of a circadian rhythm is the sleep wake cycle our body has a rhythm where once a day we sleep for an extended per period of time and then we wake for an extended period of time all biological rhythms are controlled and maintained by two things endogenous pacemakers and exogenous zit gibbers we need to explore the effect of endogenous pacemakers and exogenous sight givers on the sleep wake cycle Endo is Greek for inside and genus is Greek for producing endogenous pacemakers are internal body clocks that regulate our biological rhythm so this means that inside you and me is a clock a clock that decides when we fall asleep and when we wake up EXO is Greek for outside and zeit giber is German for time Giver exogenous zit gibbers are external cues that influence and reset our internal biological clocks so is there something inside your body that is controlling and maintaining your sleep wake cycle is there an internal clock well yes there is it's called the now not quite but it sounds like it it's called the Supra chiasmatic nucleus or the scn for short the scn is a tiny cluster of nerve cells located in the hypothalamus the optic nerve transmits electrical impulses from your eyes to your brain the place where your optic nerves cross is called the optic kaym the scn is just above them hence why it's called the Supra which means above and kosm means cross shape where the optic nerves cross so the scn is above Supra the kaym cross shape now let's apply this to The Sleep awake cycle the scn is thought to be the endogenous pacemaker for our sleep wake cycle in other words the scn is the internal clock that sets the timing of when we feel the need to sleep and when we wake in fact the scn is thought to be the master clock now you may remember from the video on the endocrine system that the pineal gland in the brain secretes melatonin a hormone that is important in helping us fall asleep it's the scn that regulates the pineal gland and thus our sleep so what about exogenous sight gibbers then the external cues that influence our rhythms while one of the most powerful external cues that influences our sleep wake cycle is light are you deaf put that light out in fact the scn our internal clock receives information about light through our eyes and the optic nerve and believe it or not the scn can even detect light when our eyes are shut when there is less light the scn stimulates the pineal gland to produce more melatonin which helps us fall asleep and when there is more light melatonin production reduces to help us feel awake light is really important for our circadian rhythm because it adjusts our internal clock the time of sunrise and sunset changes each day and so our internal clock becomes out of sync and light especially early in the morning helps to re-calibrate our internal clock to the outside [Music] world let's now consider the research into the role of both endogenous pacemakers and exogenous sight gibbers on our circadian rhythm the sleep wake cycle firstly the caral in 2000 conducted research with Chipmunks that's not singing This is singing but this is not going to be so cute a control group of 20 normal Chipmunks with perfectly intact scn were compared with an experimental group of 30 Chipmunks who had their scn's destroyed each chipmunk was radi or colored so that they could be tracked and then they were released back into their natural habitat where they were observed for 80 days what they found was that more Chipmunks who had the SC damaged were killed by weasels compared to the control group the researchers suggested that the damage to the senen affected the Chipmunk sleep wake cycle in other words they didn't know when to sleep and so this made them Restless during the night and more vulnerable to the Predator locating its pre the research demonstrates the importance of the scn in regulating our circadian rhythm the sleep wake cycle because without it we lose the Rhythm however it could be argued that we should be cautious in the conclusions we draw from this study about the Cadian Rhythm because it's based on animal research perhaps the sleep wake cycle and the particular biology involved in sleep in humans is rather different and so the results from Chipmunks may not generalize well what about research with hum humans how could we find out if we do have an internal biological clock that controls our sleep wake cycle this brings us to the research of Frenchman Michelle CIF a man who in 1962 spent two months underground in caves in the French Alps without sunlight and without clocks it was the Cold War and we knew nothing about the human sleep cycle in outer space Not only was there a competition between the US and Russia to put men into space but France France had also just begun its nuclear submarine program French headquarters knew nothing about how best to organize the sleep cycle of submariners NASA analyzed my first experiment in 1962 and put up the money to do sophisticated mathematical analysis spending this amount of time Underground in caves obviously removed his exposure to Natural Light the key exogenous zeger for our sleep wake cycle but he also wanted to see the effects of living without knowing what the time was whilst he was underground he monitored his body's activity for a number of things including when he slept so what happened to him there were many discoveries from his research some of which NASA were particularly interested in in relation to memory loss but for our purposes what he found was that despite the absence of natural daylight he maintained a regular sleep wake cycle of around 25 hours he woke up and went to sleep at regular fixed times he also unsurprisingly lost track of time I descended into the cave on July 16th and was planning to finish the experiment on September 14th when my Surface team notified me that the day had finally arrived I thought that it was only August the 20th I believed I still had another month to spend in the cave the research of sea suggests a number of things firstly we have an internal biological clock that controls our circadian rhythm that controls when we sleep and when we wake and secondly it appears that our sleep wake cycle is actually nearer to 25 hours rather than 24 and thirdly it shows the need we have for exogenous sight gibbers such as light to regulate our 24-hour sleep wake cycle in se's own words the important thing is that we Pro that there was an internal clock independent of natural day night cycle interestingly during the subsequent experiments I did with other research subjects all of the people in the caves showed Cycles longer than 24 hours there's way more to ceas research than we have time to cover in this video so if you'd like to find out more about him on the other things that happened to him in the cave then I've put some links in the description below for you however some research has raised questions about the research of Cs and others who have been studied in isolation this is because of the role of artist artificial light research conducted by Caesar ital in 1999 had the telling title of stability precision and near 24-hour period of the human circadian pacemaker they stated that previous studies on the human sleep wake cycle had failed to take into account an important factor it was understood that bright light acted as an exogenous sight Giver to the Cadian Rhythm but it was widely believed that the human Cadian pacemaker the sen was not affected by ordinary indoor artificial light sea had artificial light in his cave for those two months where he read books studied kept a diary and recorded his experiences what Caesar atel found was that when they controlled for artificial light the natural cycle of the Cadian Rhythm was 24.8 hours with very little Drift from this far closer to 24 hours than the 25 reported by others this firstly show shows how artificial light can be an exogenous sight Giver to our sleep wake cycle and secondly it undermines the findings of self isolation studies like sea in terms of the length of their sleep wake cycle because they had artificial light which may have influenced and reset their circadian [Music] rhythm beyond the sleep wake cycle there are many other examples within the body of circadian rhythms such as our body temperature digestion or when hormones are secreted these are all affected by the time of day having an understanding of these Cadian rhythms has had Real Life practical application in the treatment of illnesses this field of study is known as Chrono Therapeutics Chrono meaning time it's the study of how timing affects drug treatments and other interventions for example in this study with cancer patients they found that when in the day patients are given intravenous medication to kill cancerous cells can shape how effective the medication is and how toxic the side effects are in other words there appears to be an optimal time to deliver medication that helps fight the illness and limits the harm to the patient therefore this shows the importance of understanding Saran rhythms and their impact on human life if this video has got you all intrigued about the psychology of sleep then you need to check the description below where I've linked to a list of books and podcasts where you can explore further next next we're going to finish our Series in bioc pychology by looking at the other two rhythms ultradian and infradian which is linked below for you but now it's time to check your understanding of what we've covered in this video I'll present one question at a time you can pause the video to answer it yourself first and then press play again to reveal the [Music] answer [Music] [Music] [Music] he [Music] I hope you found this video helpful and we'll see you in the next one

Channel: Bear it in MIND

Views: 3,093

Keywords: biopsychology, circadian rhythms, michel siffre, DeCoursey chipmunks, SCN, suprachiasmatic nucleus, Biological rhythms, biopsychology revision, AQA A-level Psychology, A-level psychology revision, Paper 2 revision, Czeisler artifical light, sleep/wake cycle, endogenous pacemakers, exogenous zeitgebers

Id: gKmyCB0WNbs

Length: 13min 41sec (821 seconds)

Published: Tue Feb 13 2024