biological rhythms Flashcards
What is a biological rhythm?
- physical, mental and behavioural changes
- over a period of time
- have an important influence on the way which body systems behave
- all biological rhythms controlled by:
. ENdogenous pacemakers = internal body clock - and influenced by:
. EXogenous zeitgebers = external changes in enviro
Difference between the rhythms
- ULTRADIAN - less than 24 hours e.g. stages of sleep (approx 90 minutes)
- CIRCADIAN - last 24 hours e.g. sleep-wake cycle and body temperature
- INFRADIAN - longer than 24 hours e.g. female menstrual cycle (approx 28-35 days)
Circadian rhythms
- 24 hour cycle
- sleep wake cycle
- controlled by master endogenous pacemaker - suprachiasmatic nucleus (SCN)
- found in hypothalamus
- eyes notice change in light - gets dark - less light received by retina
- sends information to SCN
- stimulates pineal gland to release melatonin - promote sleep
- eyes detect light (EZ) - SCN reset - maintains sleep wake cycle so we are in synchrony with outside world
AO3 for Circadian rhythms: RTS by Siffre
P - RTS CR lasting around 24 hours by Siffre
E - isolated himself in cave for 6 months - his biological clock able to be free running - unaffected by EZ e.g. clocks, natural light
E - found that within few days developed consistent 25 hour cycle - continued to fall asleep and wake up on regular schedule
L - so supports sleep wake cycle is CR mainly controlled by EP - SCN
CA - some argue because Siffre’s sleep wake cycle adjusted to longer than 24 hours - EZ important in maintaining CR
AO3 for Circadian rhythms: Limitation - Siffre
P - one limitation research by Siffre - low population validity
E - conducted as case study - Siffre = only ppt
E - may not be appropriate generalise findings on sleep wake cycle beyond him - due to individual differences in sleep wake cycle and CR
- e.g. older ppl’s CR slower - more easily influenced by EZ - one of Siffre’s replications - found his CR slowed
L - lowering external validity of research into CR
AO3 for Circadian rhythms: Research by Weaver
P - despite low population validity in Siffre - research by Weaver
E - replicated research in underground bunker over 400 times - 447 ppts - found if person’s CR left free running would follow 25 hour cycle
E - supports Siffre’s findings on endogenous factors maintaining CR around 24 hours
L - so research and conclusion on CR good reliabilty
AO3 for Circadian rhythms: Strength - practical applications
P - strength research into CR - practical applications
E - basic principles of theory that CR around 24 hours maintained by EP - given researchers better understanding of negative consequences occur as result of disrupting rhythm
E - e.g. night workers experience shift work - have periods of reduced concentration (around 6am) - mistakes and accidents more likely - used by employers mange worker productivity - improves economy
L - so research into CR important part applied psych
Define Infradian rhythms (2m)
- biological rhythms that last longer than 24 hours
- one e.g. is female menstrual cycle
- operates on a 28-35 day cycle
Outline an example of Infradian rhythms
Outline the process of Infradian rhythms (4-6m)
(* = include in 8 mark essay)
- menstrual cycle is an endogenous system - typically lasts 28-35 days
- begins on first day of woman’s period - womb lining is shed - till day before her next period
- in brain pituitary gland releases FSH - activates release oestrogen from ovaries - causes egg mature
- increase of oestrogen- increases levels LH released by pituitary gland - promotes release of egg
- oestrogen develops lining of womb - progesterone helps grow thicker - ready for pregnancy
- pregnancy not occur - egg absorbed into body - womb lining comes away - leaves body - cycle begins again
- although menstrual cycle mainly endogenous system - can be affected by exogenous factors e.g. stress and pheromones
AO3 for Infradian rhythms: RTC by Russell
P - RTC IR e.g. menstrual cycle mainly governed by endogenous pacemakers - by Russell
E - asked sample women wear cotton pads under arms - pads then rubbed on upper lip of 5 sexually inactive women - repeated daily for 5 months
E - found 4/5 women menstrual cycles synchronised within one day of donor’s cycle
L - so IR of menstrual cycle can be affected by exogenous - as well as controlled by endogenous - may influence length of IR
AO3 for Infradian rhythms: Discuss - Russell - EV
P - however, Russell’s research into effect EZ on menstrual cycle - field experiment - low control over extraneous variables
E - research in ppt’s natural environment - other exogenous factors e.g. light, change diet, stress also affect IR
E - so difficult to establish cause and effect between influence of pheromones on maintaining IR
L - weakens extent Russell’s research contradict importance of EP on maintaining IR
AO3 for Infradian rhythms: Strength - evolution
P - despite methodological flaws in infradian synchrony studies - research findings explained by evolutionary psychologists
E - would have been advantageous in evolutionary past for social group to synchronise pregnancies
E - so many women breast feed at same time - one mother could take over caring for orphaned child - improve chances of survival
L - so shows synchronising IR e.g. menstrual cycle is adaptive strategy - supports exogenous influencing IR
Ultradian rhythms
- biological rhythm that occurs more frequently than once every 24 hours
- is shorter than 24 hours
- one e.g. is stages of sleep
- cycle lasts approx 90 minutes - consists of 5 stages
- alternates between REM and NREM sleep (GIVE E.G.)
- person experience up to 5 cycles per night - repeat in rhythmic pattern
What has research into Ultradian rhythms shown?
- research using EEG
- shown there are 5 distinct stages
- characterised by differences in brain, muscle and eye activity
Stage 1
- NREM (non rapid eye movement)
- light sleep
- person may be easily woken
- experience alpha waves
