Circadian rythms

Question 1

What are examples of circadian rythms?

Answer 1

• the sleep/awake cycle
• core body temperature cycle
• take a day to complete

Question 2

What is Siffre’s cave study?

Answer 2

• Siffre pronounced seed is a self-styled caveman who has spent several extended periods underground to study the effects on his own biological rhythms
• deprived of exposure to natural light and sound, but with access to adequate food and drink, Siffre re-surfaced in mid-September 1962 after two months in the caves of the southern Alps believing it to be mid-august
• a decade later he performed a similar feat but this time for six months in a Texan cave
• in each case, his free-running biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours) though he did continue to fall asleep and wake up on a regular schedule

Question 3

Which research was conducted into core body temperature?

Answer 3

• core body temperature varies by around two degrees centigrade during the course of the day
• it is at its lowest around 4 in the morning (36oC) and peaks around 6 in the evening at 38oC
• evidence suggests that body temperature may have an effect on our mental abilities: the warmer we are internally the better our cognitive performance
• Collard et al demonstrated how children who had stories read to them at 3pm showed superior recall and comprehension after a week compared to children who heard the same stories at 9am
• similarly, Gupta found improved performance on IQ tests when participants were assessed at 7pm as opposed to 2pm and 9am

Question 4

Which research was conducted into the teenage circadian rhythm?

Answer 4

• a £700,000 pro9ject, involving 106 schools will give 32,000 14-16 year-olds the chance of a lie-in and a later start to the school day to assess the impact on their educational achievement
• according to neuroscientists, teenagers circadian rhythms typically begin two hours after those of adults, so current school start times mean they wake up too early and are trying to focus when their body still needs sleep
• it also means, at bed time, they tend not to be as tired as they should be
• after a decade of researching all the available evidence, he decided to put the start of the school day back to 10am over a two-year period
• there were very positive outcomes, both academic in terms of health, said Kelly
• academic results went up, illness down and the atmosphere in school changed
• the students were much nicer to each other, it was bliss

Question 5

what are the evaluation points of circadian rhythms?

Answer 5

+shift workers are more likely to develop heart disease due to stress if changing their cycle so can have economic implications of helping workers become more productive
+practical application to timing drug dosage for better effects as drugs are best absorbed and dirstibuted at peak times of day
-small scale studies may not be representative e.g. siffre was 60 in his last study and admitted his body clock was different to when he was younger
-individual sleep/wake cycles doffer in length from 13 - 65 hours, some people are also more morning people than others

Question 6

How does practical application to shift work support Circadian rhythms?

Answer 6

• knowledge of circadian rhythms has given researchers a better understanding of the adverse consequences that occur as a result of disruption known as desynchronian trough meaning mistakes and accidents are more likely
• research has also suggested a relationship between shift work and poor health: shift workers are three times more likely to develop heart disease which may in part due to the stress of adjusting to different sleep/wake patterns and the lack of poor quality sleep during the day
• thus research into the sleep/wake cycle may have economic implications in terms of how best to manage worker productivity

Question 7

How does practical application to drug treatments support circadian rhythms?

Answer 7

• circadian rhythms co-ordinate a number of the body’s basic processes such as heart rate, digestion and hormone levels
• this in turn has an effect on pharmacokinetics that is the action of drugs on the body and how well they are absorbed and distributed
• research into circadian rhythms has revealed that there are certain peak times during the day or night when drugs are likely to be at their most effective
• this has led to the development of guidelines to do with the timing of drug dosing for a whole range of medications including anticancer, cardiovascular, respiratory, anti-ulcer and anti-epileptic drugs

Question 8

How does the use of case studies and small samples a weakness the circadian rhythms?

Answer 8

• studies of the sleep/wake cycle tend to involve small groups of participants as in the experiment by Aschoff and Weber, or studies of single individuals, as in the case of Siffre
• the people involved may not be representative of the wider population and this limits the extent to which meaningful generalisation can be made
• in his most recent cave experience in 1999, Siffre observed, at the age of 60, that his internal clock ticked much more slowly than when he was a young man
• this illustrates the fact that, even when the same person is involved, there are factors that vary which may prevent general conclusions being drawn

Question 9

how are individual differences a weakness of circadian rhythms?

Answer 9

• one further issue which complicates the generalisation of findings from studies of the sleep/ awake cycle is that individual cycles can vary
• from 13 to 65 hours
• in addition, a study by Duffy et al revealed that some people display a natural preference for going to bed early and rising early whereas some people prefer to do the opposite
• there are also age differences in sleep/wake patterns