biological rythms topic 7

What are biological and circadian rhythms?

Biological rhythms are regular cycles in behaviour influenced by endogenous pacemakers(internal biological clocks) and exogeneous zeitgebers(external biological clocks). Circadian rhythms last about 24 hours, such as the sleep/wake cycle.

The sleep/wake cycle

Exogeneous zeitgebers- effect of daylight Endogenous pacemakers- the suprachiasmatic nucleus (SCN). The SCN lies just above the optic chiasm which provides information from eyes about light. Light can reset the SCN

SIFFRES STUDY

Siffre spent long periods in dark caves to examine the effects of free-running biological rhythms, 2 months in 1962 and 6 months in 1970. In each case study, Siffres circadian rhythms settled down to about 25 hours.

ASCHOFF AND WEVER

A group of participants spend 4 weeks in a WW11 bunker deprived of natural light. All but one (whose went up to 29 hours) displayed a circadian rhythm between 24-25 hours.

FOLKARD ET AL

He studied a group of 12 people who lived in a dark cave for 3 weeks, going to bed when the clock said 11:45pm and waking when it said 7:45am. The clock gradually sped up to make a 24 hour day to a 22-hour day. Only one participant comfortably adjusted to the new regime. This suggests the existance of a strong free running circadian rhythms is not controlled by EZ.

STRENGTH OF Circadian rythms

P- One strength of circadian rhythm research is application to shift work.

E- For example, Shift work creates desynchronisation of biological rhythms. Boivin et al. (1996) found shift workers experience a lapse of

concentration around 6am so accidents are more likely. Research also suggests a link between shift work and poor health, with shift workers three times more likely to develop heart disease.

E- Thus, research into the sleep/wake cycle may have economic implications in terms of how best to manage shift work.

L- Therefore, this increases the practical application of circadian rhythm research, as it helps improve worker safety and productivity through better shift scheduling.

Counterpoint of strength 1

P- However, the research is correlational, therefore desynronisation may not be the cause of observed difficulties.

E- For example, Solomon (1993) concluded that high divorce rates in shift workers might be due to missing out on important family events.

E- This suggests that it may not be biological factors that create the adverse consequences associated with shiftwork.

L- Therefore, this lowers the internal validity of the research, as other social factors may explain the negative effects rather than biological desynchronisation.

STRENGTH

P- Another strength is real-world application to medical treatment.

E- For example, Circadian rhythms co-ordinate the body’s basic processes such as heart rate with implications for chronotherapeutics (timing medication to maximise effects on the body). Aspirin reduces heart attacks, which aremost likely in the morning. Bonten et al. (2015) found taking aspirin is most effective last thing at night.

E- This shows that circadian rhythm research can help increase the effectiveness of drug treatments.

L- Therefore, this demonstrates the usefulness of biological research to society, as applying circadian findings can make treatments more effective and cost-efficient.

LIMITATION

P- One limitation is that generalisations are difficult to make.

E- Studies of the sleep/wake cycle often use small groups of participants (Aschoff and Wever), or even single individuals (e.g. Siffre). Participants may not be representative of the wider population and this limits making meaningful generalisations. Siffre observed that his internal clock ticked much more slowly at 60 than when he was younger.

E- This suggests that, even when the same person is involved, There are factors that may prevent general conclusions being drawn.

L- Therefore, this lowers the generalisability of findings, as results from small or unique samples may not apply to the wider population.