infradian & ultradian rhythms Flashcards
what are infradian rhythms?
A type of biological rhythm with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder.
what are ultradian rhythms?
A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep (the sleep cycle.
how is menstrual cycle an example of infradian rhythms?
the menstrual cycle is governed by monthly changes in hormone levels which regulate ovulation. The cycle refers to the time between the first day of a woman’s period, when the womb lining is shed, to the day before her next period. The typical cycle takes approximately 28 days to complete.
what was Stern & McClintock’s 1998 study on the influence of exogenous factors?
-studied 29 women with a history of irregular periods.
Samples of pheromones were gathered from 9 of them at diff stages of their menstrual cycles, via a cotton pad placed in their armpit.
-The pads were worn for at least 8 hours.
-The pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants.
-On day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from the second day of the cycle, and so on.
what did Stern & McClintock find?
Stern and McClintock found that 68% of women experienced changes to their cycle which brought them doser to the cycle of their ‘odour donor.
what is SAD?
seasonal affective disorder,
it is a depressive disorder which has a seasonal pattern of onset, and is described and diagnosed as a mental disorder in DSM-5.
main symptoms are persistent low mood, general lack of activity & interest in life.
why may SAD happen?
may be due to the disruption of the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter.
what have psychologists hypothesised?
the hormone melatonin is implicated in the cause of SAD.
During the night, the pineal gland secretes melatonin until dawn when there is an increase in light.
During winter, the lack of light in the morning means this secretion process continues for longer.
affecting serotonin:
This is thought to have a knock-on effect on the production of serotonin in the brain - a chemical that has been linked to the onset of depressive symptoms.
what is the evolutionary basis strength?
- it may be explained by natural selection.
-Synchronisation of the menstrual cycle, of the kind observed in the Stern and McClintock study, is thought by some to have evolutionary value.
-For our distant ancestors it may have been advantageous for women to menstruate together and become pregnant at the same time. In a social group, this would allow babies who had lost their mothers during or after childbirth to have access to breast milk, thereby improving their chances of survival.
-This suggests that synchronisation is an adaptive strategy.
what is the mythological limitations?
-is their methodological shortcomings.
-There are many factors that may effect change to the menstrual cycle, including stress, changes in diet, exercise, etc.
-These may act as confounding variables, which means that any supposed pattern of synchronisation is no more than would have been expected to occur by chance. -This may explain why other studies (e.g. Trevathan et al. 1993) have failed to replicate the findings.
-This suggests that menstrual synchrony studies are flawed.
what is the real-world application strength & limitation?
-One of the most effective treatments for seasonal affective disorder is light therapy, a box which simulates very strong light to reset the body’s internal clock.
-Studies show this helps reduce the effects of SAD in about 80% of people (Sanassi 2014).
-Light therapy is also preferred over antidepressants to treat SAD because it is regarded as safe.
-However, light therapy can produce headaches and eye strain. Perhaps more tellingly, Kelly Rohan et al. (2009) recorded a relapse rate of 46% over successive winters, compared to 27% in a comparison group receiving CBT.
what is the most researched ultradian rhythm?
stages of sleep - the sleep cycle. Psychologists have identified five distinct stages of sleep that altogether span approximately 90 minutes - a cycle that continues throughout the course of the night. Each of these stages is characterised by a different level of brainwave activity which can be monitored using an EEG
what is stage 1?
This is light sleep where a person may be easily woken. In stage 1, brain waves are high frequency and have a short amplitude. These are alpha waves.
what is stage 2?
This is light sleep where a person may be easily woken. In stage 2, the alpha waves continue but there are occasional random changes in pattern called sleep spindles.
