Infraradian and Ultraradian rhytms Flashcards
What are infradian rhythms?
Rhythms that have a duration of over 24 hours, and may be weekly, monthly or even annually.
What are ultradian rhythms?
Rhythms that last less than 24 hours
What are 2 examples of infradian rhythms?
- The menstrual cycle
- Seasonal affective disorder (SAD)
What are 2 examples of ultradian rhythms?
- Sleep cycle
- The Basic Rest Activity Cycle (BRAC)
Outline Seasonal Affective Disorder (SAD)?
A seasonal variation in mood with some people becoming severely depressed during winter months.
During winter, the lack of light in the morning means melatonin is secreted for longer. Mealtonin has been found to have an impact in the production of serotonin which has been linked to depressive symptoms
Describe what happens during the menstrual cycle
x Lasts around 28 days and releases oestrogen- causing uterus lining to build up and then Luteinising Hormone causes an egg to be released.
x Then progesterone released to thicken womb lining
x If pregnancy doesn’t occur egg is absorbed and womb lining breaks down- menstrual flow
How many times do the 5 stages of sleep approximately occur each night?
5
Describe the 5 stages of sleep
First 4 stages= NREM (non-rapid eye movement) 1-2 light sleep, 3-4 deep sleep.
Last stage= REM (rapid eye movement)
4 Stages of NREM sleep analogy
BATS Drink Red Blood
4 Stages of NREM sleep
Pre stage 1 - High frequency beta waves punctuated by alpha waves
Stage 1 - Alpha waves reduce in frequency and replaced by Theta waves
Stage 2 - Sleep spindles (waxing and waning bursts of energy)
Stage 3 - Sleep spindles disappear and replaced by Delta waves.
Stage 4 - Delta sleep
REM sleep then Back again.
What is the basic rest activity cycle?
A 90-minute rhythm cycle characterised by a period of alertness followed by a spell of fatigue. This occurs every 90-minutes throughout the day
Evidence for exogenous factors on our menstrual cycle
Stern and McClintock (1998)
Aimed to investigate whether women’s cycles would synchronise as a result of the influence of female pheromones.
They took a group of women who had irregular periods and gathered a sample of pheromones from 9 of the women by using cotton pads and placing under their arms for 8 hours.
These were then frozen and wiped under the noses of 20 other women.
It was found that 68% of the women experienced changes to their cycle which were more in sync with their pheromone donor.
2 strengths for infradian and ultradium rhythms
Evolutionary basis of the menstrual cycle:
Menstrual synchrony (McClintock study) is thought to have an evolutionary value. For our ancestors it may have been advantageous for females to menstruate together and fall pregnant around the same time ‡ would mean new-borns could be cared for collectively increasing the chances of offspring’s survival.
COUNTER-ARGUMENT: The validity of the evolutionary perspective has been questioned. Researchers have argued that if there were too many females in sync together within a social group, this would produce competition for the highest quality males (and thereby lowering the fitness of any potential offspring).
Practical application for SAD:
Research on infradian rhythms and SAD has allowed the development of effective treatment for SAD. One of the most effective treatments for SAD is phototherapy. This is a lightbox that simulates very strong light in the morning and evening. It is thought to reset melatonin levels in people with SAD. This relieves symptoms in up to 60% of sufferers.
2 limitation for infradian and ultradian rhythms
Individual differences: Studies into ultradian rhythms tend to show significant variability among individuals, which suggests that there are innate differences in ultradian rhythms that are not accounted for in controlled lab settings. Tucker et al. (2007) found significant differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4 (just before REM sleep). This demonstrates that there may be innate individual differences in ultradian rhythms.
Methodological limitations Sleep studies Sleep research often takes place in controlled lab conditions using specialised equipment such as monitors and sensors glued or taped to the PPs head. This can feel uncomfortable for some and overall, quite intrusive so may alter their natural sleep patterns. The studies therefore have low ecological validity as the sleep patterns observed in the lab setting may not accurately represent the ultradian rhythms that occur naturally in real life.
