Infradian and ultradian rythms Flashcards
What is infradian rhythm?
- a type of biological rhythm with a frequency of less than one cycle in 24 hours such as menstruation and seasonal affective disorders
- lasts longer than a day
What is ultradian rhythm?
- Lasts less than a day
- sleep cycle of 5 stages that last 90 mins each
What is the menstrual cycle?
- governed by monthly hormone changes that regulate ovulation
- lasts from the womb lining coming apart to the day before the last period which is usually every 28 days
- oestrogen causes an egg to be released, progesterone helps womb lining thicken for pregnancy which comes away if the egg is reabsorbed
Which research was conducted into infradian rhythms?
- 29 women with a history of irregular periods were studied to see if their cycles could be synchronized
- 9 women had their pheromone sample taken at different stages of their menstrual cycle via cotton pad to armpit which was treated with alcohol and frozen to be applied to the upper lip of the other 20 women every day of their cycle
- 70% of women experienced changes in their cycle that brought them closed together
What is seasonal affective disorder?
- a depressive disorder which has a seasonal pattern as it is triggered during winter months when theres less daylight
- during the night the pineal gland secretes melatonin until dawn when there is an increase in light
- during the winter months less light means this process takes longer which effects the production of serotonin which ca cause depressive symptoms
What are the stages of sleep?
- stage 1 and 2: sleep escalator: light sleep with slowing brainwave patterns called alpha waves which lead to even slower theta waves
- stage 3 and 4: deep sleep with delta waves which are slower and have great amplitude
- stage 5: in REM sleep the body is paralyzed yet the brain is active and the eyes are rapidly moving as dreams are occuring
What are the evaluation points of infradian and ultradian rhythms?
+the evolutionary basis of the menstrual cycle:
-mythological limitations of synchronized studies many factors that may effect change in a woman menstrual cycle
+evidence supports the idea of distinct stages in sleep: REM activity during sleep correlated with vividity dreaming
+animal studies: sea urchins release pheromones into the surrounding water so other urchins in the colony will eject their sex cells simultaneously
How does the evolutionary basis of the menstrual cycle support infradian and ultradian rhythms?
- menstrual synchrony is thought by many to have an evolutionary value
- for our ancestors it may have been advantageous for females to menstruate together and therefore fall pregnant around the same time
- this would mean that new-borns could be cared for collectively within a social group increasing the chances of the offspring’s survival
How do methodological limitations in synchronisation studies support infradian and ultradian rhythms?
- there are many factors that may effect change in a woman menstrual cycle including stress, changes in diet, exercise other than synchrony that might act as confounding variables which reduces the internal validity
- in addition research typically involves small samples of women and relies on participants self-reporting the onset of their own cycle so is less reliable which reduces external validity
How does evidence that supports the idea of distinct stages in sleep support infradian and ultradian rhythms?
- a landmark study by Cement and Kleitman monitored the sleep patterns of nine adult participants in a sleep lab
- brainwave activity was recorded on an EEG and the researchers controlled for the effects of canine and alcohol
- REM activity during sleep. Was highly correlated with the experience of dreaming, brain activity varied according to how vivid dreams were and participants woken during dreaming reported very accurate recall of their dreams
- nevertheless, this study suggests that REM sleep is an important component of the ultradian sleep cycle
how are animal studies a strength of infradian and ultradian rhythms?
- much of the knowledge of the effects of pheromones on behaviour is derived from animal studies
- the role of pheromones in animal sexual selection is well documented
- for instance, the fact that sea urchins release pheromones into the surrounding water so other urchins in the colony will eject their sex cells simultaneously
