Infradian & ultradian rhythms

• Infradian rhythm def (with examples)


  -takes 24hr+ to complete

  -eg menstrual cycle, SAD
• Ultradian rhythm def (with example)


  -Takes less than 24hr to complete

  -eg sleep cycle
• Is menstrual cycle part of the nervous or endocrine system?


  Endocrine
• What rhythm is menstrual cycle


  Infradian
• Is the menstrual cycle endogenous or exogenous?


  It is an endogenous system, but may be influenced by exogenous factors (eg cycles of other women)
• What did Stern and McClintock study


  Studied the exogenous influence on menstrual cycle
• Who did Stern & McClintock study


  29 women w/ irregular periods
• How did Stern & McClintock carry out their study


  -gathered sample of pheromones (from cotton will pads on arm it for 8hrs) of 9 women at diff stages of menstrual cycle

  -cotton wool w/ pheromones were treated w/ alcohol, frozen &

  - rubbed on upper lip of ppt

  -Day 1= pad from start of menstrual cycle

  -Day 2= from 2d day of cycle etc
• Conclusion to Stern & McClintock study


  -found 68% women experienced changes to their cycle, closer to cue of "odour donor")

  -shows menstrual cycle can synchronise as a result of female pheromones (an exogenous zeitgeber)
• What type of rhythm is SAD


  infradian (can be circannual)
• Symptoms of SAD


  fatigue, oversleeping and difficulty staying awake, craving, inability to cope, social withdrawal, lacking energy, irritability, low mood etc
• What are the causes of SAD


  -body produces higher melatonin than normal

  -Lower levels during winter can disrupt bodys internal clock (pineal gland secretes melatonin for longer as its darker)

  -lack of sunlight may lead to lower serotonin levels
• 5 stages of sleep... ...
• Describe Stage 1 of sleep


  -Non REM

  -transition from wakefulness to asleep

  -lasts 10 mins

  -characterized by slower bpm, breathing & relaxation of muscle
• Describe Stage 2 of sleep


  -Non REM,

  -Period of light sleep (before deeper sleep)

  -20mins long

  -further slowing of bpm & breathing

  -brain starts producing sleep spindles (rapdi, rhythmic brain activity)
• Describe stage 3 & 4 of sleep


  -Lasts 20-40mins

  -Muscles so relaxed

  -Bpm & breathing slow to lowest level, slower brain waves
• Describe stage 5 of sleep

  -REM (rapid eye movement)

  -90mins after sleep

  -Deepest sleep

  -Temporary paralysis of body (to not move in dreams)

  -When STM turns to long-term memory

  -Brain activity speeds up (resembles brain awake)

  -Correlated w/ dreaming
• How can you measure brainwave activity in each different stag

  EEG
• Evaluation for infradian cycle... ...
• Name the strengths of infradian cycle


  +Evolutionary basis of menstrual cycle

  +Evidence supporting diff stages of sleep

  +Practical application for SAD
• How is evolutionary basis of menstrual cycle a strength


  +synchronisation of menstrual cycle advantageous for females to fall pregnant collectively to increase chances of offspring survival or even produce competition for natural selection (adaptive evolutionary strategy)
• How is evidence supporting the distinct stages a strength

  +Demont & Kleitman monitored sleep patterns of 9 adults sleep pattern in sleep lab using EEG (controlled alcohol &^ caffeine intake)

  +REM highly correlated w/ dreaming (brain activity varied depending on how vivid dreams are)
• How is practical application a strength

  +A treatment for SAD is phototherapy (strong light in morning)

  +Treats melatonin levels & relieves symptoms

  +Placebo effect of 30%, casting doubt on chemical influence on phototherapy
• Name weakness of infradian cycle


  Methodological problems
• How is methodological problems a weakness in Stern & McClintock study


  -Lots of confounding variables

  -Cycles syncing may be up to chance

  -Small cycle
• Ultradian evaluation... ...
• Name strengths of ultradian cycle


  Improved understanding
• How is improved understanding a strength

  +Higher understanding of age related change

  +Sleep/wake cycle reduces w/age

  +Growth hormone is mostly produced during s/wc so it's reduced in older ppl

  +May result in various issues in old age eg relaxation & medication may be used for deeper sleep
• Name weaknesses in ultradian evaluation


  -Indv differences

  -The sleep lab
• How is indv differences a limitation


  -Significant variation between ppl

  -Big diff between ppt in terms of duration of each sleep stage (esp 3&4)

  -Biologically determined diff- so hard to describe normal sleep in meaningful way
• How is sleep lab a disadvantage

  -Uses controlled settings

  -Research includes extraneous factors eg noise & temp

  -involved ppt being attached to artificial machinery (cap of electrodes) so doesn't represent normal sleep