Biorhythms

HideShow resource information

Circadian Rhythm

A01: controlled by exogenous zeitgebers (light and dark) and endogenous pacemakers (SCN), SCN causes protein production creating internal rhythm activating the pineal gland which releases melotonin causing drowsiness, occurs when it is dark and when it is light protein production stops, rythm can be syncronised by external cues, light sensitive cells in the retina, alignment to new cues e.g changing time zones, is called entrainment

IDA: Biological/environmental determinism, pre-determined factors control the cycle suggesting we have no control over it, SCN and zeitgebers must work together, in reality we have some control over the cycle e.g going to sleep later or waking up earlier than the cycle would allow

EVIDENCE: Morgan - removed the SCN from hamsters and the sleep wake cycle disappeared, transplanted mutant SCN and reciever picked up mutated cycle. Michel Siffre - spent 2 months in a dark cave, cycle lengthed to 25 hours. Miles - reported case of a man blind from birth who had a 24.9 hour cycle despite exposure to clocks/radios. 

A03: use of animals and case studies reduces population validity, consistent results suggest reliability, lab based research gives high control and internal validity

WIDER EVALUATION: practical applications, not exposing to light before sleeping (Mariane Figeuro) as 2 hour exposure creates 22% melotonin reduction

1 of 12

Disrupting Biorhythms - Jet Lag

A01: caused by crossing several time zones, symptoms include memory loss, nausea, headaches, confusion etc, Phase delay causes lengthening of cycle, phases advance causes shortening of cycle which causes more problems, social jet lag is the discrepancy between biological clock and social clock

IDA: Socially sensitive, people will always have to fly and suffer these symptoms, however there are practical applications

EVIDENCE: Klein - confirmed view that flying west to east causes worsejet lag, suggestes that one day per time zone crossed is needed for full recovery. Schwartz - looked at baseball teams from the west and east coast, teams that had to fly east to play had significantly fewer wins.

A03: cannot prove that jet lag caused fewer wins, no cause and effect can be establish, non scientfic evidence, consistent results suggest reliability

WIDER EVALUATION: practical applications, understanding can be used to reduce jet lag symptoms e.g melotonin pills

2 of 12

Disrupting Biorhythms - Shift Work

A01: employees who do regular night shifts or alternating shift patterns, interferes with the SCN and zeitgebers, increased risk of obesity, heart problems, divorce, and suggested that even cancer.

IDA: Socially sensitive, people will always have to do shift work even though there are serious health and family implications, however the theory can be used to reduce the risk of these things.

EVIDENCE: Blackemore - chemical plant where workers had a three week rotating shift patter, beginning with night, then evening, then morning, lab animals who experienced this pattern suffered heart disease and shorter life span. Cziesler - same chemical plant, rotated shift pattern forwards, workers reported feeling better/less tired, management reported increased productivity and fewer errors. Hansen - found a link between shift work and breast cancer

A03: same sample used in both studies reduces population validity, animals mean we cannot generalise results, consistent results suggest reliability

WIDER EVALUATION: Practical applications, changing shift work patterns to cause phases delay could reduce associated health risks

3 of 12

Infradian Rhythm

A01: menstrual cycle controlled by the endocrine system and exogenous zeitgebers, FHS promotes growth of follicle, Oestrogen, builds up endometrium, LH a surge causes ovulation, Progesterone builds endometrium to maximum thickness, HCG maintains output of Oestrogen and Progesterone. Pheremones are thought to influence the cyle through the olfactory system.

IDA: a relevant theory is the evolutionary approach as related to reproduction, menstruation is stopped in 'unsuitable' mothers as increased risk of an unhealthy baby, cannot explain while male family members release hormones that reset the cycle as there's no reproductive advantage.

EVIDENCE: Russel - 5 women who were exposed tp the pheremones of another women, 4 out of 5 of the women's cycles synchronised to within a day of the odour donor. McClintock - male pheremones reset the biological clocl, observation of women who work with men having shorter cycles. Reinerg - spent 3 months in a dimly lit cave and her cycle shortned to 25.7 days

A03: Strong scientific evidence gives good support, low population validity, observation and evidence for pheremones cannot establish cause and effect

WIDER EVALUATION: Very little is know about the influence of pheremones, affects half the population makes it surprising about the limited knowledge, further research is needed.

4 of 12

Ultradian Rhythm

A01: what happens within sleep, every cycle lasts 90 minutes, move through stages 1,2,3,4 and then REM, and back through to stage 1, as cycle repeats the stages we enter decrease, periods of REM increase while other stage lengths decrease. 

IDA: entirely biological approach. cycle is not affected by cognition and we have no control over it, we are unaware it is happening, they are universal and pre-determined. Scientific measurement reinforces the use of the biological approach

EVIDENCE: Division of Sleep Medicine at Harvard Medical School - repeatedly missing a nights sleep, alcohol, caffine and beta blockers all reduce the effectiveness of the ultradian rhythm.   Wehr - plunged young adults into 14 hours of darkness a day, within 4 weeks sleeping cycle had adapted to 3-5 hour sleep, 1-2 hour awake, 3-5 hour sleep. Ekirch - found historical records that supported the fragmented sleep pattern found by Wehr, this dissapeared by the 1920s

A03: Scientific research gives control, objectivity, replicability, sleep labs create control increasing validity but they are an artificial setting reducing ecological validity

WIDER EVALUATION: Practical application (harvard), suggests there are environmental influences, suggesting it is not 100% biological, reductionist

5 of 12

Stages of Sleep

A01: Stage 1- high frequency, low amplitude, fall in heart rate/temperature. Stage 2- large slow theta waves, sleep spindles and K complexes, Stage 3- long slow delta waves. Stage 4- long slow delta waves, growth hormone. Stage 5- REM, high frequency, low amplitude, paradoxical sleep.

IDA: Biologically determinist as it cannot account for individual differences as it suggests we have no control or influence over the stages of sleep. This limits out understanding of the stages, however it would be unethical to manipulate someone's sleep to find the precise relationship between biology and sleep.

EVIDENCE: Sharpio - hour and a half more sleep two following days of a marathon, more stage 4. Empson - disruption of stage 4 causes back pain and muscle stiffness. Dement - REM deprived participants were more irritable, aggressive, less able to focus.

A03: Sharpio was a natural study reducing control but scientific measures were used increasing objectivity. Dement was scientific but in artificial settings reducing ecological validity. Consistent findings suggest reliability

WIDER EVALUATION: importance of stage 4 emphasised, little is know about stage 2, should it be counted as it's own stage? what role does it play? further research needed.

6 of 12

Lifespan Changes in Sleep

A01: Babies, REM=50-60%, cycle shorter than 90 minutes, Adolescents, REM=20%, experience phase delay, 60's, 50% reduction in stages three and four, 70s/80s, REM=10% and by 90s, no stage three or four sleep.

IDA: this offers practical applications, teenagers experience phase delay so schools could start later to counter act this, research has shown this to be effective.

EVIDENCE: Breedlove - babies need more REM sleep to help brain grow and organise, Wolfson and Carskadon - 3000 american students, average 7.3 hours sleep, 1/4 get 6.5, A* students get an hour more sleep. Monkstean High School - start lessons at 10am, 8% drop in general absence, 27% drop in persistent absence. Senile Dementia - early sufferes have reduced stage 3 and 4 sleep

A03: Wolfson - large sample but all american, surveys create demand characterstics, natural school study means we cannot establish cause and effect

WIDER EVALUATION: Webb from the university of Florida found marked individual differences in life span changes, meaning we cannot generalise sleeping patterns to all

7 of 12

Evolutionary Theories of Sleep

A01: Hibernation theory (Webb), sleep reduces energy spent as movement/heat, sleep will increase when potential for energy loss is high. Predation Theory (Meddis), exposure to predators and food intake determins how much we sleep, explains why humans sleep at night as we have poor night vision. Both suggest sleep itself is not vital.

IDA: Impossible to test empirically, theory lacks validity and so amounts to just speculation. Differences between Webb and Meddis' theories highlight issues with using the evolutionary approach to explain the function of sleep.

EVIDENCE: Alison Cicchetti - 39 animal species, found a correlation between risk of predation and amount of time spent asleep. Hibernation - some animals hibernate in winter when it is cold and food is scarce. FFI - suggests that sleep is vital as the disorder results in death

A03: research on animals cannot be generalised to humans, reducing population validity, not empiracle evidence as it is based on observation alone, lack replicability

WIDER EVALUATION: The theory may no longer be applicable to humans, we are not at risk of predation and do not have to conserve food. Suggests the theory is not valid

8 of 12

Restoration Theories of Sleep

A01: Oswald suggested that REM is for repair of the nervous sytem while NREM is for bodily repair. The growth hormone released in stage 4 from the pituatory gland promotes neural protein synthesis. Horne differentiated between optional (stages1-3) and core(stages4-5) sleep. He suggested that sleep is needed for psychological repair and that bodily repair occurs during waking and sleeping rest periods. The growth hormone is a consequence of sleep no its purpose.

IDA: These theories offer practical applications. Highlights importance of stage 4 sleep, perhaps this could be used to enhance the amount of stage 4 sleep we get. Memory functioning has also been linked to sleep.

EVIDENCE: Sharpio - ultramarathon, slept an hour and a half longer two following days and more time dedicated to stage 4. Dement - REM deprived Ps were more irritable, aggressive and less able to focus. Randy Gardener, Peter Trip, FFI

A03: naturally occuring evidence means cannot establish cause and effect. However scientific measures were used increasing internal validity and objectivity as less chance of bias. Case studies reduce population validity. Consistent results suggest reliability

WIDER EVALUATION: oversimplifying function of sleep, cannot explain memory functioning, reductionist, limits our understanding 

9 of 12

Sleep Walking

A01: Diathesis-stress model suggests there are predisposing and environmental factors that influence sleep walking. Occurs in slow wave sleep in a state of incomplete arousal, delta waves or high frequency beta waves which are characteristics of being in an awake state. maturation of key neural circuits means most people grow out of sleep walking, increased slow wave sleep e.g alcohol increases sleepwalking.

IDA: nature/nurture debate. Biological factors are the cause and environmental factors increase the likelihood, suggests that nature is more important, nature simply affects how likely you are to suffer.

EVIDENCE: Hublin - 11,000 Ps (1045 MZ, 1899 DZ), concordance rate, 55% MZ, 35% DZ, 89% of men and 86% of women who reported adulthood sleepwalking also experienced it as a child. Zadra - 40 Ps, deprived of sleep, 1st night 50% sleepwalk, 2nd night 90% sleepwalk. Lecendreux - higher incidence of sleepwalking among MZ twins (50%) than DZ twins (12%)

A03: large sample but all finnish, controlled environment and scientific measures

WIDER EVALUATION: associated withh stress/depression so treating these could reduce sleepwalking, can be dangerous and people have even murdered while sleep walking so it must be controlled

10 of 12

Narcolepsy

A01: focuses on the role of genes and hypocretin, genetic variation on chromosome 6, called the HLA complex, predisposed an individual to narcolepsy, creates an autoimmune response to cells that produce hypocretin, a neurotransmitter that controls arousal and wakefulness. a hypocretin deficiency predisposes someone to narcolepsy. can also be created by certain flu jabs

IDA: Biologically determinst, suggests we have no free will over sleep behaviour, may make someone feel powerless as it suggests there is no way to reduce symptoms

EVIDENCE: Dement - mice who could not produce hypocretin displayed sleep attacks and cataplexy, Mignot - identified defective gene hypocretin receptor 2 in dogs using positional cloning, encodes protein, cannot recognised messages e.g wakefulness. Mignot - 25-31% concordance rate for MZ twins and 1-2% for 1st degree relatives

A03: Lab studies provide controlled conditions improving validity, use of animals reduces population validity, cannot generalise, scientific measures improve objectivity, replicability

WIDER EVALUATION: cannot explain why environmental changes reduce symptoms, e.g strict medtime, suggests it is not entirely biological. However has created useful treatments e.g modafinil

11 of 12

Insomnia

A01: predisposing factors e.g genetic vulnerability and a state of hyperarousal, precipitating factors e.g stress or environmental change, perpetuating factors, these maintain the insomnia once the precipitating factors have gone e.g expectation of poor sleep, these are key to the development of chronic primary insomnia 

IDA: interesting debate of free will and determinsim, interaction of factors causes insomnia suggesting the individual has limited control reducing free will, however less environmental stress can reduce it making them empowered.

EVIDENCE: Watson - twin study, suggested 50% variance in risk of insomnia is due to genetics, Morin - daily measures of stressful events, measured pre-sleep arousal, 21 days of questionaires, insomniacs percieve life as more stressful and had increased arousal, link between stress and amount of sleep, Dement - sleep state misconception, never took more than 30 minutes for individuals to fall asleep

A03: Correlation means no cause and effect, Dement was highly controlled, use of questionares may create demand characteristics, artificial environment

WIDER EVALUATION: Practical applications, environmental stability, less stress etc

12 of 12

Comments

No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all Biological Rhythms resources »