Ultradian and Infradian Flashcards
What are ultradian rhythms?
Bodily cycles than span for less than a day
What is the main example of an ultradian rhythm?
Sleep cycles, undergone daily when people sleep
How long does the sleep cycles last for?
90 minutes, moving through 5 different stages
How does the sleep cycle stages begin?
When the person is awake and displays Beta waves on an EEG machine
What is displayed as the person starts to relax?
Alpha waves, as they are in calm-wakefulness
What happens in stages 1 and 2?
Light sleep, displaying theta waves
What happens in stage 2 regarding stimuli?
Although asleep, the person can still respond to external stimuli and so are easily woken
What happens in Stage 3 & 4?
Slow Wave Sleep, where sleep is increasingly deeper and people are more difficult to wake.
What happens in SWS?
Repair work takes place such as the production of growth hormones, cell growth and protein synthesis
-Sleep walking and night terrors may occur
What is the final stage of sleep?
REM, where brain waves mimic those of the awake brain. Associated with dreaming, body is paralysed so only the eyes can move.
As the night progresses, how do the sleep cycles change?
More REM and less time in other stages
A criticism of research into sleep stages is that it is assumed when an individual is in REM, they are dreaming…
- One study, participants woken mid REM
- Many reported dreams, but dreams occurred outside of REM and some were not dreaming in REM
What is a problem with the assumption that dreaming only and always occurs in REM?
- Link provides underlying support for theories like that of the theory dreams are a psychological read out of REM electric signals
- Theories rely on accuracy of link
A strength of research into sleep cycles is that it was conducted in a lab experiment…
- strict control of variables such as light
- EEG machine: empirical data that can be analysed objectively
- Increases reliability
Alternatively, the nature of such studies as lab experiments may limit the research…
- Lab setting is artificial and not representative of natural sleeping environments
- Quality/quantity of sleep affected, skewing results
- Lacks ecological validity and generalisability
How long do infradian rhythms last for?
More than 24 hours but less than one year
What is a main example of an infradian rhythm?
Menstrual cycle
What role does I rhythm play in the menstrual cycle?
- Regulates oestrogen and progesterone secretion
- Stimulate release of egg and growth of lining of womb
- When unfertilised, bleeding for 3-7 days
What is a lesser known I monthly cycle?
- Male monthly rhythm
- 49 to 102 days, variation of both body temperature and morning altertness
Both the menstrual and male monthly rhythm thought to be controlled internally, with the hypothalamus acting as the endogenous pacemaker, but…
Evidence has shown exogenous zeitgebers to play a role too
A limitation of research into the menstrual cycle is the assumption that they are controlled solely by a persons internal biology…
- Underarm sweat from donor women applied to the upper lips of female participants
- Despite pairs never meeting, menstrual cycles became synchronised
- Pheromones in sweat can influence the menstrual cycle
Research into the menstrual cycle is determinist, why?
Because it is widely described as an endogenous rhythm
What is an example of the determinism behind the menstrual cycle?
- PMS, psychological and physical symptoms
- Mrs English, a PMS sufferer drove her car into her married lover following an argument
What happened to Mrs English?
- Charged with murder
- Decided she would be placed on probation instead on grounds of PMS
- Argument backed up by doctor
In relation to Mrs English, what does this deterministic explanation assume?
- PMS is beyond the control of women, meaning they cannot be held liable for their actions
On the other hand, evidence has been found to contrast the belief that bodily rhythms are beyond our control…
Stress hormone ACTH (helps waking up process) found in people told to wake up earlier than usual - cycle is not entirely biologically determined and can be influenced by our own free will
What is another example of an Infradian Rhythm?
SAD, a depressive cycle taking place over a few months
What happens to a SAD sufferer?
- Severely depressed in Winter months (cold and dark)
- Recover in Summer (light and warm)
- Less sunlight leads to more melatonin production which decreases serotonin, linked with depression and other mental disorders
However, SAD may be a disrupted circadian rhythm rather than the outcome of an infradian rhythm…
- Routine change in Winter, people may go to bed earlier but get up at same time
- Gives impression to bio system of time shifting, a feeling like jet lag
- Not entirely biological as can be affected by external factors
What is one application of research into SAD?
- Phototherapy
- Strong artificial lights (10k+ LUX) to alter melatonin and serotonin levels
- Daily use reported to ease depression and lethargy
However, why has phototherapy been criticised?
- Placebo effect, although placebo was less effective, 32% did show some improvement from a placebo
- Partially psychological rather than biological determined??
