HideShow resource information
  • Created by: Will
  • Created on: 28-05-14 15:23

Circadian rhythms

Lasts about 24hours eg sleep wake cycle

Michael siffre spent long periods in a cave with no light found his cycle normally remained at 24hours but sometimes shifted

Ashcroft and weaver placed pp in underground bunker pp cycle was 24-25 hours

Body temperature

Folkard tested memory on children asked to recall book when read at either 9am or 3pm able to recall more at 3pm

Hord and Thompson found no difference in body temp and cognitive performance


Cortisol lowest at midnight and highest at 6am high levels mean more alert

1 of 16


Czeisler stated that cycle length varies between 13-65hours


Increased temperature could be due to high arousal levels

2 of 16


Lasts for more than 24hours but less then a year
Menstrual cycle controlled by hormones and is a 28day cycle
Russel studied the synch of women's menstrual cycle and found due to pheromones their cycle synchronised, as sweat of one women was placed on others and they synced
Turk evolutionary approach women synchonised their pregnancy in means of sharing parenting duties
SAD low levels of melatonin cause depression and in winter it is darker so it is secreted more
Deterministic as saying SAD is inevitable but bright light in the morning can resynchronise the melatonin system
Premenstrual syndrome was thought to be a psychological problem but it is now a physiological problem which is cause by hormonal changes related to infra divan rhyth

3 of 16


Less then 24 hours

Cycle is normally 90minutes

Stages 1&2=relaxed heart rate slows and temperature drops easily awoken(Nrem sleep)

Stages 3&4=deep sleep and slow wave sleep(Nrem sleep)

Rem sleep is associated with dreaming and our brain and eyes are active

In deep sleep body repair takes place and the production of growth hormone occurs

As night progresses SWS gets shorter and Rem sleep gets longer


Dement and kleitman showed this by waking up pp when in rem sleep and found pp highly likely to report dreaming, although sometimes they weren't dreaming

Individual differences due to age

4 of 16

Endogenous pacemakers

The pacemaker is the suprachiasnatic nucleus
SCN acts as an internal clock which keeps the body at 24 hours
Is affected by light as lots of light reduces production of melatonin and no light produce melatonin
Melatonin encourages sleep
Stephen & zucker used rats that had 12 hours of light and and 12 of dark. They drank more and more active during the dark period compared with a group with damaged SCNs and they eliminated normal circadian rhythm of activeness and drinking, so SCN is main pacemaker
Morgan transplanted SCN of mutant hamsters( circadian rhythm of 20 hours) into normal hamsters who then developed the mutants rhythm
Siffre case study on how important light is
Animal studies

5 of 16


These are external cues to help control bio rhythms and synch them
Both endogenous and exogenous need to work together
Light can reset the SCN and Campbell and Murphy found when light shone on back of knee=reset of body clock
Social cues eg meal times and appropriate sleep times.
Davidson says all body cells have their own oscillating rhythms eg meal times reset cells in the heart and liver
Luce and Segal people in arctic sleep for 7 hours a day even though it is always light in summers
Nature v nurture
Stephens artificial lighting disrupts circadian rhythms and thus disrupts melatonin production and can cause women working in well lit place to develop breast cancer
Bolivian found rhythms can be controlled by dim lighting though bright light was more effective

6 of 16

Shift work and shift lag

Shift work is working patterns that enable companies to work constantly
Decreased alertness- Boivin 1996 night worker experience a circadian trough of decreased alertness
Sleep deprivatio- hard to sleep during day due to light and noise
Chernobyl happened at 1:30am
Knutson those that work shift work for 15 years are 3 times more likely to develop heart disease
Solomon shift workers experience social disruptions and divorce rates are up to 60%
Czeisler studied shift workers found high illness rates, sleep disorders and high levels of stress due to their body clocks being out of synch. He suggested they rotated shifts to phase delay forward rotating shifts. 9 months much better
Artificial light

7 of 16

Jet lag

Rapid change in zeigebers
Winter calculated that it is one delay to adjust to every hour change
Phase delay=going back in time east to west
Phase disruption= ahead in time west to east
Recht- baseball teams won 37% when travelling west to eats and 44% win when travelling east to west (phase delay)
Cho found cabin crew have raised levels of stress
Individual differences
Waterhouse disrupted sleep and hormone patterns to cabin crew led to decrease in cognitive performance and female cabin crew complained about their menstrual cycle.
Melatonin supplement can help recover from jet lag

8 of 16

Lifespan changes in sleep

Infancy- 16 hours
Short sleep cycle as sleep cycle less then adults
In first 6 months circadian rhythm is established and by one year they are mainly sleeping at night
Go through active sleep before entering quiet sleep
By 5 years similar EEG paterns to adult
12 hours sleep more rem
Boys sleep more then girls
Common to experience night terrors
Adolescent 9-10hours sleep
Changes to phase delay awake more at night find it harder to get up
Old age sleep walking is rare but insomnia isn't
8 hours sleep but find it difficult to go to sleep waking up through out night =phase advance
Reduced sleep linked with health problem
Slow wave sleep reduced in old age easier to wake

9 of 16


Babies sleep is adaptive mechanism to make their parents life easier
Infants greater amount of rem sleep can be explained by immaturity of the brain
Need for being fed regularly, so wake in night
In teens Crawley says hormonal changes can also explain the upset to the circadian clock
Kripke found in one million men and women found that people sleeping for only 6or 7hours had a reduced morality rate
Redid sleep in old age is due to reduce physical ability
Less sleep could explain their reduced alertness

10 of 16

Functions of sleep

Restoration theory- Oswald 1980 proposed SWS is for body repair. Rem is for brain recovery
Neurotransmitter a that have fallen are replenished during sleep
Babies sleep and this is for massive brain growth
There is a neg correlation between quantity of rem sleep and brain weight in new born babies
During SWS the release of growth hormones stimulate protein synthesis
Conserve energy
Shapiro 1981 found marathon runners slept extra hour 2 nights following race (physical recovery)
Horne and minard gave pp hard tasks to see if increased sleep but it didn't
Stern & Morgans that rem is linked to this synthesis of neurotransmitters used up in daytime activities
With new born babies their brain grows rapidly with millions of new synaptic connections and therefore more neurotransmitters are produced
Reductionist focuses solely on physiological process

11 of 16


Sleep must be adaptive
Mammals need to preserve energy(hibernate) Webb and conserve energy important for small animals
Predator prey status- meddis says that sleep keeps prey animals safe at times when normal activities are impossible
Environment- animals either sleep at night or day and are adapted to be active in part of every 24 hours and for the remainder they will be inactive
Predator or prey- prey animals are more vulnerable than predators especially when asleep
Sleep site- does the animal sleep in a relatively safe burrow or in an exposed area
Size- large animals sleep more then small

12 of 16


Cicchetti found that species who were prey slept less although there were exceptions ie rabbits
Zeppelin & rechtschaffen found small animals had higher metabolic rate sleep more then larger animals
Capellini previous research was flawed as data was not standardised and found neg correlation between metabolic rate and sleep which doesn't support the energy conservation
Sleeping overnight conserves very little energy for humans
Theories show effect but not cause

13 of 16


Difficulties in going to sleep and staying asleep
Primary insomnia- due to bad sleep habits or expectations of sleeping problems because of previous cause (depression) defined by DSM
Secondary insomnia- exists from something else therefore it is a symptom of the main cause and there is an environmental, medical or psychiatric problem (sleep hygiene, heart disease or depression)
Older people and women more likely to suffer
Sleep apnoea where individuals stop breathing and personality kales says insomniacs would internalise the problem rather then acting it out
CBT can treat change neg thoughts and educate on good hygiene
Diathesis stress model that we may inherit faulty mechanisms to produce insomnia but needs another environmental factor
Watson found 50% of the variance in the risk for insomnia could be attributed to genetic factors

14 of 16

Sleep disorders

Narcolepsy- trouble maintaining sleep and triggered by emotions extreme sleepiness
Explanations- a malfunction of rem sleep as symptoms match rem sleep
Mutation in HLA the mutation cause WBC to destroy hypocretin and reduced hypocretin= wakefulness is difficult to maintain honda found this
Mutation to hypocretin- role in maintaining wakefulness . Narco dogs have abnormal gene for processing hypocretin Lin.
Mignot found HLA was also found in a lot of normal Pop as well as narcoleptics
Nishino low levels of hypo in narcoleptics
Animal ethics
Psychological explanations Lehman propose could be due to sexual fantasies

15 of 16

Sleep walking

Is a disorder most common in childhood affect 20%children &3%adults- hublin
Incomplete arousal in sleepwalking. EEG recordings show a mixture of SWS delta waves &beta waves from awake state so mixture of awake and sleep waves
Sleepwalking occurs when person is woken but brain arousal is incomplete
In children they have more SWS and their SWS is not sufficiently developed.
Lecendreux showed that SW is genetic MZ 50% concordance DZ 15%
Broughton found frequency of SW in first degree relatives of an affected subject is at least 10times greater then in general pop
Pressman suggests more research is needed to understand the link between factors like alcohol and SW

16 of 16


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all Sleep resources »