Biological Rhythms: Infradian And Ultradian Rhythms Flashcards
What is the menstrual cycle an example of?
Infradian rhythms
What does the menstrual cycle refer to?
The time between the first day of a woman’s period to the day before her next period
How long does the typical menstrual cycle take to complete?
28 days
During each menstrual cycle what causes the ovary to develop an egg and release it?
The hormone Oestrogen
What happens after ovulation?
The hormone progesterone helps the womb lining grow thicker, readying the womb for pregnancy
What happens if pregnancy doesn’t occur?
The egg is absorbed into the body, the womb lining comes away and leaves the body
What type of system is the menstrual cycle?
Endogenous system
What does evidence suggest the menstrual cycle may be affected by?
Exogenous factors e.g. other woman’s cycles
What did Stern and McClintocks’ study show?
How menstrual cycles may synchronise as a result of the influence of pheromones
What did Stern and McClinton study?
29 women with a history of irregular period
What was gathered from the 9 women?
Pheromones by a cotton pad placed under there armpit
How long were the cotton pads worn?
For at least 8 hours to ensure the pheromones were picked up
What were the pads treated with?
Alcohol and frozen to be rubbed on the upper lip of another participant
What happened on day 1?
Pads from the start of the menstrual cycle were applied to all 20 women
What happened on day 2?
Everyone was given a pad from the second day
What did Stern and McClinton find?
68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’
What is Seasonal Affective Disorder?
A depressive disorder which has a seasonal pattern of onset
What are the main symptoms of SAD?
Persistent low mood, lack of activity and interest in life
When are the symptoms of SAD triggered?
During the winter months when the number of daylight hours becomes shorter
What type of Infradian rhythm is SAD?
Circannual rhythm
What other type of rhythm can SAD be classed as?
Circadian rhythm
What have psychologists hypothesised?
The hormone melatonin is implicated in the cause of SAD
What happens during the night?
The pineal gland secretes melatonin until dawn when there is an increase in light
What happens during winter?
The lack of light in the morning means this secretion process continues for longer this is thought to have a knock on effect on the production of serotonin in the brain
Menstrual synchrony evaluation: Research has explained it may be by natural selection
- synchronisation of the menstrual cycle is thought to have evolutionary value
- for people in the past it may have been advantageous for women to menstruate together and become pregnant at the same time
- this would allow babies who had lost their mothers during or after childbirth to have access to breast milk thereby improving their survival chances
- suggests synchronisation is an adaptaive strategy
Synchronisation evaluation: methodological shortcomings
- many factors effect the menstrual cycle like stress or changes in diet
- these factors may act as confounding variables which means any supposed pattern of synchronisation is no more than would have been expected to occur by chance
- this may explain why other studies have failed to replicate findings - Trevathan et al
- menstrual synchrony is flawed
What is an example of an ultradian rhythm?
The sleep cycle
How many stages have psychologists identified for sleep?
5 that altogether span 90 minutes
What is each stage characterised by?
A different level of brainwave activity which can me monitored using an EEG
What is stages 1 and 2?
Light sleep where someone may be easily woken
What types of brain waves are stage 1?
High frequency with short amplitude - alpha waves
What type of brain waves are stage 2?
Alpha waves but there are occasional random changes in pattern called sleep spindles
What is stages 3 and 4?
Deep sleep or slow wave sleep
What brain waves are stages 3 and 4?
Delta waves with lower frequency and high amplitude - it’s difficult to wake someone at this point
What is stage 5?
REM - the body is paralysed but brain activity closely resembles being awake
What brain waves occur in REM sleep?
Theta waves and the eyes occasionally move around, thus rapid eye movement
What brain waves occur in REM sleep?
Theta waves and the eyes occasionally move around, thus rapid eye movement
What is expected during REM?
Dreams however these can also occur in deep sleep
Ultradian rhythm evaluation: improved understanding of age-related changes in sleep
- sleep scientists have observed SWS reduces with age
- growth hormone is mostly produced during SWS therefore this reduced in older people
- according to Eve van Cauter et al the resulting sleep deficit may explain various issues in old age such as reduced alertness
- in order to increase SWS, relaxation and medication may be used
- suggests knowledge of ultradian rhythms has practical value
Ultradian rhythms evaluation: significant variation between people
- Tucker et al found large differences between participants in terms of the duration of each sleep stage particularly 3 and 4
- Tucker et al suggests that theses differences are likely to be biologically determined
- difficult to describe ‘normal sleep’ in any meaningful way
Ultradian rhythms evaluation: significant variation between people
- Tucker et al found large differences between participants in terms of the duration of each sleep stage particularly 3 and 4
- Tucker et al suggests that theses differences are likely to be biologically determined
- difficult to describe ‘normal sleep’ in any meaningful way
Why can SAD be classed as a circadian rhythm?
the experience may be due to disruption to the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter
