BIOPSYCHOLOGY - infradian and ultradian rhythms Flashcards
what is an infradian rhythm?
a type of biological rhythm which is more than 24 hours. eg menstruation and seasonal affective disorder
outline the menstrual cycle.
- 28 days
- increase in hormone oestrogen causes ovary to develop egg and release = ovulation
- progesterone helps womb lining to grow thicker for pregnancy
- no pregnancy = egg is absorbed into body = womb lining leaves the body (menstrual flow)
Outline Stern and McClintock (1998)
- demonstrated hoe menstrual cycle may synchronise as a result of the influence of pheromones
- 29 women with irregular periods
- pheromone samples of 9 women collected via cotton pad placed in armpit
- pads were then treated with alcohol and then rubbed on upper lip of other ps
FINDINGS = 68% of the women experienced changes to their cycle which brought them close to the cycle of their ‘odour donor’
what is SAD?
seasonal affective disorder
= depressive disorder which has a seasonal pattern of onset.
persistent low mood triggered during winter months when daylight hours become shorter.
- a circannual rhythm = yearly cycle
- during winter the secretion of melatonin is longer = knock-on affect on production of serotonin = depressive symptoms
What are Ultradian rhythms?
A type of biological rhythm which is less than 24 hours such as stages of sleep.
What is the sleep cycle?
A cycle that continues throughout the course of the night.
Each stage is characterised by different level brainwave activity which can be monitored using an EEG.
Stages one and two of the sleep cycle?
Light sleep where a person may be easily woken.
1. Brainwaves a high frequency and have a short amplitude = alpha waves
2. Alpha waves continue but there are occasional random changes in pattern called sleep spindles.
stages 3 and 4 of sleep cycle?
Deep sleep or slow wave sleep.
Brain waves are delta waves with lower frequency and higher amplitude.
Difficult to wake up someone at this point.
What is stage five? REM?
The body is paralysed.
Brain produces theta waves and the eyes occasionally move around (rapid eye movement)
Dreams are experienced during REM sleep.
give strengths into research of infradian rhythms?
+ menstrual synchrony research can be explained by natural selection = synchronisation of menstrual cycle is thought to have evolutionary value. E.g. for distant ancestors it may have been advantages for women to menstruate together and become pregnant at the same time so that babies who have lost their mothers during or after childbirth could have access to breastmilk improving the chances of survival.
= synchronisation is an adaptive strategy
+ real world application = treatment for seasonal affective disorder is like therapy which resets the bodies internal clock. Studies show that this reduced 80% peoples affects of SAD. Light therapies preferred over antidepressants because it is safe.
Give limitations of research into infradian rhythms?
Methodological limitations
There are many factors that may affect change to the menstrual cycle such as stress, changes to diet, exercise. These are confounding variables which means that synchronisation has occurred by chance.
Evaluate research into ultradian rhythms
+ improved understanding of age related changes in sleep
eg sleep wave cycle reduces with age. Eve can cauter et al - sleep deficit may explain issues in old age such as reduced alertness. To improve this relaxation in medication may be used = knowledge of ultradian rhythms has practical value
- there is significant variation between people.
eg tucker et al found differences between participants in terms of duration of each sleep stage. Therefore these differences are likely to be biologically determined. It is difficult to describe normal sleep in any meaningful way.
