Infradian and ultradian rhythms BP Flashcards
infradian rhythm
a type of biological rhythms with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder
ultradian rhythm
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)
What is the menstual cycle governed by?
monthly changes in hormone level with regulate ovulation
what does a cycle refer to?
Cycle refers to the first day of a woman’s period (shedding the lining) to the day before her next period
how many days is a typical cycle?
A cycle is typically 28 days but can be anywhere between 24-35 days
What causes the egg to develop and release (ovulation)?
oestrogen
What does progesterone do?
helps the womb lining grow back
synchronising the menstual cycle
Despite the menstrual cycle being an endogenous system, evidence suggests that it could be influenced by exogenous factors like other women’s cycles
Stern and McClinton’s pricedure
- Studied 29 women with irregular periods
- Gathered samples of pheromones from 9 women at different stages of their cycles via a cotton pad under their armpit
- Pads were worn for 8 hours then treated with alcohol and frozen
- Pads were rubbed on upper lip of the other participants
- On day 1 → pads from start if cycle were applied and so on
Stern and McClinton’s findings
68% of women experienced changed in their cycle which brought them closer to their ‘odour donor’
seasonal affective disorder
SAD is a depressive disorder with a seasonal pattern of onset and is part of DSM-5. Symptoms are triggered in winter months where days are shorter.
symptoms of seasonal affective disorder SAD
- Persistent low mood
- General lack of activity and interest in life
- Change in weight
What type of infradian rhythm is SAD?
circannual rhythm because it is on a yearly cycle. But it is also classed as a circadian rhythm as it could be experienced due to disruption of the sleep/wake cycle (darker longer in winter).
What casues the secretion of melatonin from the pineal gland not stop in the morning?
During winter, the lack of light in the morning means the secretion of melatonin from the pineal gland doesn’t stop. This has an effect on the production of serotonin in the brain (linking to depressive symptoms).
the stages of sleep
The stages of sleep (the sleep cycle) have been intensively researched. 5 stages have been identified that span about 90 minutes per cycle and each stage is characterised by a different brain wave that can be measured with an EEG.
stage 1and 2
light sleep, easily woken, high frequency brainwaves and short amplitude (alpha waves), random changes in stage 2 called sleep spindles
stage 3 and 4
deep sleep, slow wave sleep, delta waves, lower frequency and higher altitude, difficult to wake up, dreams can occur
stage 5
paralysed body but brain remains active, theta waves, eyes occasionally move, rapid eye movement REM, dreams can occur
infradian rhythms strength
I
Evolutionary basis
May be explained by natural selection
infradian rhythms strength
D
- Stern and McClinton’s research on synchronisation may have evolutionary value
- Ancestors may have found it convenient to menstruate together and fall pregnant at the same time
- Babies who had lost their mothers could then still access breast milk which increases their chance of survival
infradian rhythms strength
E
Synchronisation is an adaptive strategy
infradian rhythms limitation
I
Methodological shortcomings
infradian rhythms limitation
D
- Many factors could affect menstrual cycle eg stress, diet, exercise
- Confounding variables means that synchronisation could have just occurred by chance as explained by Trevathan et al
infradian rhythms limitation
E
Menstrual synchrony studies are flawed
infradian rhythms RWA
Light therapy is one of the most effective treatments for seasonal affective disorder, where a light is used to reset someone’s body clock. Sanassi found that it helped 80% of people.
ultraradian rhythms strength
I
Improved understanding of age-related changes in sleep
ultraradian rhythms strength
D
- SWS reduces with age
- Growth hormone is reduced in old age as a result of this
- Cauter et al found that this sleep deficit may explain various issues in old age eg reduced alertness
- Relaxation and medication can be used to increase SWS
ultraradian rhythms strength
E
Knowledge of ultradian rhythms has practical value
Ultradian rythms limitation
I
Significant variation between people
Ultradian rythms limitation
D
- Tucker et al found large differences between participants in terms of duration of each sleep stage, mainly 3 and 4
- These differences are biologically determined
Ultradian rythms limitation
E
Difficult to describe ‘normal sleep’ in a meaningful way
Dement and Kleitman
- First to use EEG to identity the stages of sleep
- They would wake them up periodically and ask them what they had just been experiencing
- If they were woken up during stages 1-4 they would report nothing but if woken up during REM they would report dreaming
- Thus suggesting that there are 90 minute cycles and not one continuous dream
