Outline and Evaluate Infradian Rhythms Including Research Essay

Infradian rhythms atomic number 18 biological rhythms that last for more than 24 hours. They are controlled by the hypothalamus, an endogenetic pacemaker which requires input from exogenous zeitgebers so the rhythm can run correctly. An example of an infradian rhythms is the mentstrual turn. This is controlled by the pituary gland which is an endogenous pacemaker. The pituary gland releases hormones which cause an egg in the ovaries to ripen and produce oestrogen. Whilst it is cognise to be biological due to its universal nature, there are grand individual differences such as the length of time and the age the catamenial cycle begins.Reinberg conducted research into infradian rhythms where a woman spent 3 months in a cave only with dim inflammationing. Her sleep/wake cycle slightly lengthened whereas her catamenial cycle shortened suggesting that light affects menstrual cycles. However, this is a case study which kernel it needs generalisability even more so as there are l arge individual differences with the menstrual cycle. On the other exit, Russell et al applied female donors sneaky sweat which has been combined with alcohol to the upper lips of female participants.The menstrual cycles of the participants began to synchronises and then suggesting that pheromones act as exogenous zeitgebers. Pheromones are biological substances similar to hormones tho are secreted into the air and then transmitted to other animals of the same species, or in this case humans, before being absorbed into their bloodstream. However, despite the try out size being sm all(prenominal) it was a well controlled single sieve study meaning that the participants didnt know what experimental group they were in.McClinock and behind provided further support for the study when they establish pheromones in donors sweat affected the recipients menstrual cycles, therefore suggesting that exogenous zeitgebers deplete a regulating effect. It may be the cases the synchronised p eriods have an evolutionary significance because it allows women that are living together to synchronise pregnancies so they can share child care. However, it has also been found that women working in proximity to men have shorter cycles an evolutionary advantage which provides more opportunity for pregnancy.Likewise, the purpose of a menstrual cycle is to conserve energy. Therefore it is separate to restrict periods of fertility, highlighting the need for endogenous control. On the other hand there are side effects of the menstrual cycle such as pre menstrual tension which has been associate with increased aggression. Lewis found that pre menstrual tensions has been cited as a defence in criminal trials. A wink infradian rhythm is Seasonal Affective Disorder (SAD). It involves having severe depression in the winter months.Levels of melatonin are higher in winter and may impart to increased depression and sleepiness. However, it has led to a treatment called phototherapy which i s being candid to bright lights for several hours a day in order to decreased the effect of too much serotonin. This in turn, lowers melatonin levels. Hamster research again has provided us with more knowledge of infradian rhythms. Male hamsters have annual rhythms of testosterone secretion base on the amount of light that occurs each day. As the breeding season begins, the days lengthen thus when it ends, they shorten.Rusak and Zucker made lesions in the SCN, the Suprachiasmatic Nucleus, part of the hypothalamus in a hamster which unmake their annual breeding cycles and led to male hamsters secreting testosterone all year. The 24 hour clock that daily light levels were measured against was destroyed so the seasons couldnt be determined. Carlson found that if it was less than 12 hours of light for hamsters, it is winter where if it more than 12 hours it is summer, and therefore the breeding season. However, the research was encroaching(a) and led to brain damage, meaning it ca used harm to the hamster.As it has also been conducted on animals, it cannot be generalised because it lacks population validity despite being informative. Circa-annual rhythms which means they happen once a year are also examples of infradian rhythms. When study migration, Gwinner kept groundless birds in cages exposing them to 12 hours of light and 12 hours of darkness. This lack of external stimuli led to migratory restlessness thus suggesting there is endogenous control. However, it may be triggered by the availability of food, an exogenous cue.As the wild birds were kept in cages, they also experienced harm because they were not in their natural setting either. Pengelly and Fisher conducted research into hibernation. Similar to Gwinner, they controlled squirrels artificially by exposing them to light 12 hours a day followed by 12 hours of darkness, memory the temperature at 0 degrees. The squirrels hibernated from October to April. However, as the animals were not in their n atural habitat, the studies lacked ecologic validity because it was artificial.The research findings are positive as they have found the existence of endogenous pacemakers regulated by exogenous zeitgebers. However, to an extent the findings are deterministic because we need exogenous zeitebers to help our endogenous pacemakers as it has been found in studies by Siffre and Aschoff and Weber that without external cues, our biological rhythms are pokey than what they need to be. In addition, some of the research is idiographic because they are depressed samples and or case studies meaning they lack population validity.