What is a biological rhythm
A change in body processes or behaviour in response to cyclical changes within the environment
24 hours rhthym name and example
Circadian eg sleep wake cycle
Under 24 hours rhythm and examples
Ultradian eg stages of sleep
Over 24 hours rhythm and examples
Infradian eg menstrual cycle or seasonal affective disorder
All biological rhythms are affected by what two things
Endogenous pacemakers - body’s internal clock
Exogenous zeitgebers - external factors in the environment
Siffre’s research
- In 1962, a French cave explorer, Michel Siffre spent two months living in total isolation in a subterranean cave without access to clock, calendar or sun.
- Sleeping and eating only when his body told him to, his goal was to discover how the natural rhythms of human life would be affected by living “beyond time” (known as ‘free running’)
- After a 2 month cave stray, he then lived in a cave for 6 months! The lights came on when he woke and went off when he slept. He settles into a sleep/wake psychology of 25-30 hours- usually juts beyond the usual 24 hour cycle
- His sleep/wake cycle had become desynchronized
Aschoff and Wever
Aschoff and Wever (1976) conducted a study where a number of participants were placed in a bunker for 4 weeks with no natural light. They settled into a sleep wake cycle of 25-27 hours.
However the participants were in bunk beds together so they could have taken exogenous queues from each other.
Czeisler et al
Czeisler et al (1999) argued that the use of bright lights in Siffre’s experiment was highly artificial. They therefore did in experiment in low light conditions which resulted in a circadian cycle of 24 hours and 11 minutes
Folkard et al
- Folkard et al (1985) wanted to investigate the extent to which we can alter circadian Rythms by altering the external queues.
- they isolated 12 participants from natural light for three weeks (in a dark cave) and sped up the clocks so that only 22 hours passed a day (unknown to the Ps who thought the clocks were normal 24r hour clocks)
- none of the Ps could adjust comfortable to the pace of the clock which shows the strength of endogenous pace makers
AO3 night shift
- shift work has been found to lead to desynchonization of circadian rhythms and can lead to adverse cognitive and physiological effects
- research has shown that night shift worker suffer a concentration lapse at 6am, therefore increasing the likelihood of accidents and shift workers and also three times more likely to suffer from heart disease as a result from the stress of adjusting to sleep/wake cycles
- this research therefore has many economic implications in terms of maintaining worker productivity and preventing accidents in the work place
AO3 pharmacokinetics
- by understanding circadian rhythms and their impact on health, it can help determine the best time to administer drug treatments
- for example the risk of heat attack is greatest in early morning so drugs can be taken at night but not released until when they will be most effective at dusk
- this mean that there are peak times for administration and dosage of a variety of drugs that treat a range of disorders that increase their efficacy
AO3 resreach support
- Michael Siffre spend two months in the caves of the southern Alps deprived of light and sound, determining that his circadian rhythm remained between 24-25 hours.
- Further research support by Wever and Aschoff had a group of participants live in a WWII bunker for four weeks and found that the sleep/wake cycle lasted just under 25hours concluding that exogenous zeitgebers (light hours’/meal times) may have an impact mediating the cycle. - - However other research by Folkard set participants sleep and wake times that initially fit with a 24-hour day but then unknown to the participants sped up the clock so the cycle only lasted 22 hours. This had a significant impact on the participants who were adversely affected by the change from the set 24-25 hours
- this suggests that the body’s internal clock is set 24-25 hours in the absence of external queues, and is intolerant of any major alternations to sleep and wake cycles, through processes such as shift work and jet lag
AO3 case study
- the Siffre study was only on one individual and the Folkhard, Wever and Aschoff studies were conducted on only a handful off people
- consequently it is impossible to generalize these results to whole populations of people as there may be some individual differences in the research sample that makes these Ps respond to the changes of the sleep/wake cycle in atypical ways
- for example Siffre noted that when he went into the cave at 60 years old his body responded very different with his body clock following more of a 48 hours cycle
- and Czeisler has found evidence that cycles can vary by as much as 13-65 hours
- this suggests that results cannot be generalized from these small samples onto everyone, as factors such as age and gender may have significant impacts on our circadian rhythms
AO3 poor control in studies
- in the case studies the exposure to artificial lights such as torches/phones was not controlled
- it was assumed it was only natural light that has an influence on our biological rhythms, however research by Czeisler found that dim artificial lighting could adjust the circadian rhythm between 22-28 hours
- this means that the revisits to the original studies may lack validity and the sleep wake cycle may very considerably more
- additionally the impact of artificial lighting on our circadian rhythms also has practical implications when it comes to the use of electronic devices such as IPads and smartphones during diffnet times of the day
