biological rhythms : circaidian rhythms ao3 Flashcards
(4 cards)
Issues with animal studies
P: 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,
E; 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.
E; 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.
L: 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. Thus this research has the issue of low ecological validity.
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 Michel Siffre.
E: Siffre 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
- Research by czeisler et al stated that prev studied failed to take into account how artificial light is an exogenous zeitgeber (similar to natural light) that affects the SCN and our circ rhythms.
- Siffre had artificial in his cave for those two months where he read books and kept a diary detailing his experiences. These artificial light could have influenced his seen wake cycle.
*Czeisler found that when artificial light was controlled for the natural cycle was 24..18 and didnt drift from this. Hence showing how atrial light in an ex zeitgeber which affects our sleep wake (prev believed this wasn’t true) and undermines the finding s of self isolation studied in terms of length of sleep wake where artidia light could have affected circ rhythm
