Biological rhythms: Infradian and Ultradian Flashcards
(10 cards)
What are biological rhythms?
-Distinct patterns of changes in body activity that conform to cyclical time periods
-They are influenced by Endogenous pacemakers (internal body clocks) and external cues (exogenous zeitgebers)
What are infradian rhythms?
- Have duration greater than 24 hours, may last days, weeks, months or years
-e.g. Menstrual cycle and Seasonal affective disorder
Describe Kathleen Stern and Martha McClintock (1998) research into studying sychronisation of menstrual cycles?
-studied 29 women with history of irregular periods
-Samples of pheromones were gathered from 9 of the women at different stages of menstrual cycle via a cotton pad placed on their armpit
-pads worn for 8 hrs so pheromones picked up
-Pads treated with Alcohol and frozen then rubbed on the other girls upper lip
-On the first day, pads were given to all 20 women and so on.
-Found 68% of women experienced changes which brought them closer to their cycle
What is seasonal affective disorder (SAD)?
-a mood disorder caused by the body’s reaction to low levels of sunlight in the winter months
-Known as winter clues
-researchers hypothesised that as it is darker more melatonin is produced which has a knock on effect on production on serotonin which has be linked with onset of depressive symptoms.
Strengths of research into Infradian rhythms
-Evolutionary basis: It is thought that it would have been an advantage to our distant ancestors to have menstrual cycles sync and happen at the same time as this would lead to mothers have children at the same time. As a result of this, if the mother was to die during childbirth the child would still have access to breast milk. This suggests synchronisation is a human adaptation.
-Real life application: Treatments for SAD is light therapy which is a bright box which resets the bodys internal clock. Sanassi (2014) reduced the symptoms of SAD by 80%.
HOWEVER, it can cause headaches and eye strain. Furthermore Kelly Rohan et al. (2009) recorded a relapse rate of 46% over successive winters which is more than comparison group (27%) which received CBT.
Weaknesses of research into Infradian rhythms
-Methodological issues: Many factors which could cause changes in menstrual cycle such as stress, diet and exercise. These are confounding variables. These means synchronisation may have occured by chance. This explains why other research has found it difficult to replicate the findings ( Trevathan et al 1993)
What are Ultradian rhythms?
-A type of biological rhythm which is less than 24 hrs and happens many times a day
-e.g. Stages of sleep - each cycle through stages is 90 mins
Describe the stage of sleep
-Stage 1+2: Light sleep when they are easily woken and brain waves are alpha waves ( high frequency and short wavelength). In stage 2 sleep spindles happen which are spikes in brain activity
-Stage 3+4: Deep sleep or Slow wave sleep (SWS), delta waves (lower frequency and higher amplitude), not easily woken up
-Stage 5: Rapid eye movement (REM) sleep; body is paralysed but eyes move, theta waves (resembles the brain when awake), dreams mostly occur in this stage.
Strengths of research into Ultradian Rhythms
-Improved understanding: sleep scientists observed SWS reduces with age. In SWS growth hormone is released. Eve Van cauter et al. (2000) suggest this is why older people have issues such as alertness. This can be remedied with medicine or relaxation.
Weaknesses of research into Ultradian Rhythms
-Individual differences: Adrienne Tucker et al (2007) found large differences between people in duration of sleep stages, particularly stage 3 and 4. Tucker suggested these are biologically determined. This makes it difficult to describe normal sleep.
-Low ecological validity: research into sleep often conducted in sleep labs. This makes the research useful in limiting all extraneous variables such as noise and temperature which may affect a person’s sleep.
However, low ecological validity as the person will be connected to heavy machinery leading a person to being uncomfortable and therefore not sleeping in a way that does not represent normal sleep patterns.
