infradian rhythms Flashcards
what are infradian rhythms? give 2 examples
a type of biological rhythm that take longer than 24 hours to complete. Menstrual cycle and seasonal affective disorder are 2 examples of this
what is SAD?
seasonal affective disorder is a depressive disorder which has a seasonal pattern of onset and is diagnosed as a mental disorder. The main symptoms are low mood and general disinterest in life. it is triggered during the winter months when daylight hours get shorter. It could also be triggered by a disruption of the sleep wake cycle due to prolonged periods of daily darkness in winter
wha type of infradian rhythm is SAD?
circannual as it’s subject to a yearly cycle
what hormone can be held responsible for SAD? why?
melatonin, because during the night the pineal gland secretes melatonin until there’s an increase in light. During winter, the lack of light in the morning means that this process occurs for longer. this has a knock on effect on the production of seretonin
explain stern and McClintocks study and the results
they demonstrated how menstrual cycles may synchronise as a result of pheromones. They studied 29 women with a history of irregular periods. Samples of pheromones form 9 women were taken at different stages of their cycle via a cotton pad in their armpit. these pads were worn for 8 hours and treated with alcohol then frozen to be rubbed on the upper lip of other ppts. On day 1, pads from the start of the cycle were applied to 20 women, on day 2 they were given a pad from the second day of the cycle and so on. They found that 68% of women experienced changes to their menstrual cycle which bought them closer to the cycle f their “odour donor”
explain one strength of infradian rhythms (evolution)
menstrual synchrony may be explained by natural selection. Synchronisation may have evolutionary value. Distant ancestors may have menstruated together and become pregnant at the same time. This would allow babies who had lost their mothers during childbirth still had access to breast milk so they had a higher chance of survival. This suggests that synchronisation is an adaptive strategy
explain one limitation of infradian rhythms (methodological)
one of their limitations is their methodological shortcomings. There are many factors that may affect the menstrual cycle such as stress, diet, exercise. These may act as confounding variables which means any supposed pattern of synchronisation is nothing more than due to chance. This may explain why other studies struggle to replicate findings. This suggests the studies are flawed
