Outline and Evaluate Infradian Rhythms Including Research
Infradian rhythms are biological rhythms that last for more than 24 hours. They are controlled by the hypothalamus, an endogenous pacemaker which requires input from exogenous zeitgebers so the rhythm can run correctly.
An example of an infradian rhythms is the mentstrual cycle. 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 known to be biological due to its universal nature, there are large individual differences such as the length of time and the age the menstrual cycle begins.
Reinberg conducted research into infradian rhythms where a woman spent 3 months in a cave only with dim lighting. Her sleep/wake cycle slightly lengthened whereas her menstrual cycle shortened suggesting that light affects menstrual cycles. However, this is a case study which means it lacks generalisability even more so as there are large individual differences with the menstrual cycle. On the other hand, Russell et al applied female donor's underarm sweat which has been combined with alcohol to the upper lips of female participants. The menstrual cycles of the participants began to synchronises therefore suggesting that pheromones act as exogenous zeitgebers. Pheromones are biological substances similar to hormones but 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 sample size being small it was a well controlled single blind study meaning that the participants didn't know what experimental group they were in. McClinock and Stern provided further support for the study when they found pheromones in donor's sweat affected the recipient's menstrual cycles, therefore suggesting that exogenous zeitgebers have a regulating effect.
It may be the cases the synchronised periods have an evolutionary significance because it
An example of an infradian rhythms is the mentstrual cycle. 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 known to be biological due to its universal nature, there are large individual differences such as the length of time and the age the menstrual cycle begins.
Reinberg conducted research into infradian rhythms where a woman spent 3 months in a cave only with dim lighting. Her sleep/wake cycle slightly lengthened whereas her menstrual cycle shortened suggesting that light affects menstrual cycles. However, this is a case study which means it lacks generalisability even more so as there are large individual differences with the menstrual cycle. On the other hand, Russell et al applied female donor's underarm sweat which has been combined with alcohol to the upper lips of female participants. The menstrual cycles of the participants began to synchronises therefore suggesting that pheromones act as exogenous zeitgebers. Pheromones are biological substances similar to hormones but 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 sample size being small it was a well controlled single blind study meaning that the participants didn't know what experimental group they were in. McClinock and Stern provided further support for the study when they found pheromones in donor's sweat affected the recipient's menstrual cycles, therefore suggesting that exogenous zeitgebers have a regulating effect.
It may be the cases the synchronised periods have an evolutionary significance because it