biological rhythms : circaidian rhythms ao3 Flashcards
Issues with animal studies
There are limitations when generalising findings from aninal studies to
humans, particularly due to differences in physiology and the number and types of circadian rhythms, thus limiting the ecological validity of such findings
The influence of the SCN has been demonstrated in animal studies conducted by DeCoursey et al. (2000). In their research the SCN in the brains of 30 chipmunks were destroyed, before they were returned to the wild and observed. It was found that their sleep/wake cycles almost entirely disappeared and a significant proportion of them had been killed by predators by the end of the study, highlighting the importance of the SCN in mammals. However, this research is flawed because of its use of chipmunks. Although structures such as the SCN and the pineal gland exist across mammalian species, humans would respond very differently to manipulations of their biological rhythms.
This is not only because we are different biologically, but also because of the vast differences between environmental contexts. This makes research carried out on other animals unable to explain the role of endogenous pacemakers in the biological processes of humans.
Additionally, DeCoursey et al’s study raises various ethical issues that need to be considered: animals were exposed to considerable harm, and subsequent risk when they were returned to their natural habitat.
Strength - application to chronotheraputics
P: One real-world application of circadian rhythm research is chronotherapeutics - the study of how timing affects drug treatments.
E: The specific time that patients take their medication is very important as it can have a significant impact on treatment success. It is essential that the right concentration of a drug is released in the target area of the body at the time that the drug is most needed.
E:For example, the risk of heart attacks is greatest during the early morning hours after waking up.
Therefore chronotherapeutic medications have been developed with a novel drug delivery system.
These medications can be administered before the person goes to sleep at 10pm, but the actual drug is not released until the vulnerable period of 6am to noon (Evans and Marain, 1996)
E: This shows that research into circadian rhythms has not just furthered our understanding of the human body, but research applications have led to to the improvement of treatment for patients with a variety of conditions requiring drug therapy.
Evidence from siffre- strength
P: Evidence for a free-running circadian rhythm comes from a series of study conducted by French cave explorer, Michel Siffre.
E: On several occasions Siffre has subjected himself to long periods of time living underground in order to study his own circadian rhythms.
E: While living underground he had no external cues to guide his rhythms - no daylight, no clocks or radio. He simply woke, ate and slept when he felt it was appropriate to do so. The only thing influencing his behaviour was his internal body clock i.e. his free-running body clock.
L: In several of his studies Siffre spent several months underground and every time his natural circadian rhythm to between 24-25 hours, which provides support for free-running circadian rhythms.
Counterpoint to siffres
P: A limitation of research into the sleep/wake cycle is the tendency to involve small groups of participants or single individuals e.g. Siffre.
E: The people may not be representative of the wider population and this limits the extend to which meaningful generalisations can be made.
E: In his most recent cave experience Siffre (1999) observed, at the age of 60, that his internal clock ticked much more slowly than when he was a young man.
L: This illustrates the fact that even when the same person is involved, there are factors that vary which may prevent general conclusions being drawn.
