Biopsychology

Question 1

What is the nervous system?

Answer 1

A specialised network of cells, it is the primary communication system which uses electrical and chemical signals.

Question 2

What is the nervous system divided into?

Answer 2

Central nervous system (CNS) and the peripheral nervous system (PNS).

Question 3

What is the CNS?

Answer 3

Brain and spinal cord.

Question 4

What is the PNS divided into?

Answer 4

Somatic nervous system (SNS) and automatic nervous system (ANS).

Question 5

What is the ANS divided into?

Answer 5

Sympathetic and parasympathetic.

Question 6

What is the somatic nervous system?

Answer 6

System that controls conscious/voluntary activities. Made up of afferent and efferent neurons.

Question 7

What is an afferent neuron?

Answer 7

Sensory neurons carrying sensory information.

Question 8

What is an efferent neuron?

Answer 8

Motor neurons carrying instructions to effectors.

Question 9

What is the PNS made from?

Answer 9

Nerves.

Question 10

What is the autonomic nervous system?

Answer 10

Controls internal organs and glands (automatic responses).

Question 11

What is the parasympathetic branch of the ANS?

Answer 11

Returns the body to routine, day to day activities (rest and digest).

Question 12

What is the sympathetic branch of the ANS?

Answer 12

Stress related activities (fight or flight).

Question 13

What do the parasympathetic and sympathetic branches do when operating together?

Answer 13

Maintain homeostasis.

Question 14

What is the endocrine system?

Answer 14

Regulates all biological processes in the body, made up of glands and hormones, working alongside the nervous system.

Question 15

Explain the process of the fight or flight response.

Answer 15

Stressor is perceived.
Signal sent to hypothalamus which activates the sympathetic branch of ANS.
Adrenal medulla (part of adrenal gland) releases adrenaline into the bloodstream and releases noradrenaline.
Pupils dilate, increased breathing and heart rate, muscle tension, glucose released.
After stressor is gone, parasympathetic branch of ANS dampens response and returns the body to testing state.

Question 16

Name the types of neurons.

Answer 16

Sensory - carry messages from PNS to CNS, long dendrites, small axons.

Relay - connect sensory neurones to motor neurones, short dendrites, long axons.

Motor - connect CNS to effectors, short dendrites, long axons.

Question 17

Explain the process of firing a neuron.

Answer 17

When resting, the inside of the neuron is negatively charged compared to the outside.
When activated, the neuron becomes positively charged for a second.
This causes an action potential to occur.
And this created an electrical impulse.

Question 18

Explain chemical transmission between neurons.

Answer 18

Signals within a neurone are transmitted electrically, but between neurones is chemically. When the electrical impulse reaches the end of the neuron (presynaptic terminal), the release of a neurotransmitter is triggered from tiny sacs called presynaptic vesicles.
Bind to receptors or post synaptic neurone
Produce inhibitory or excitatory effects.

Question 19

What are neurotransmitters?

Answer 19

Chemicals that diffuse across the synapse.

Question 20

Where do axons take the electrical signals?

Answer 20

Towards the synapse.

Question 21

Where do dendrites take the electrical signal?

Answer 21

Away from the synapse.

Question 22

What is excitation?

Answer 22

When a neurotransmitter increase the positive charge of a postsynaptic neuron.

This makes an increased likelihood that the post synaptic neuron will pass the electrical impulse.

Question 23

What is inhibition?

Answer 23

When a neurotransmitter increases the negative charge of a postsynaptic neuron.

This makes a decreased likelihood that the post synaptic neuron will pass on the electrical impulse.

Question 24

What is summation?

Answer 24

Whether the post synaptic neuron fires or not. The excitory and inhibitory influences are summed up.

Question 25

Ways of studying the brain

Answer 25

Post mortem - studying the brain after death, determine whether observed behaviour related to structural abnormalities.

Electroencephalogram (EEG) - measuring electrical activity in the brain, measuring wave patterns to help diagnose conditions.

Event-related potential (ERP) - isolating electrophysiological response of the brain to a specific sensory, motor or cognitive event, statistically analysing EEG data.

Functional magnetic resonance imaging (fMRI) - measure brain activity while a person is carrying out a task, detects radio waves from changing magnetic fields, detect which areas are rich in oxygen and therefore active.

Question 26

Strengths of post mortem

Answer 26

Allows more detailed examination of anatomical and neurochemical aspects (not possible with non-invasive scanning techniques).

Develop understanding of schizophrenia - Harrison (2000) due to post mortem examinations, researchers have been able to identify structural differences and evidence for neurotransmitters which are associated with the disorder

Question 27

Limitations of post mortem

Answer 27

Can lead to inaccurate findings - length of time between death and post mortem, drug treatments and age are all confounding influences. Findings might lack internal validity making it difficult to draw conclusions.

Retrospective - unable to follow up anything that arises from the examination, so conclusions drawn are often limited.

Question 28

Strengths of EEG

Answer 28

High temporal resolution - takes a reading from an active brain making it more accurate.

Useful for clinical diagnosis - epileptic seizures can be picked up on an EEG so it can help to diagnose brain abnormalities.

Question 29

Limitations of EEG

Answer 29

Can only detect activity in superficial regions of the brain, not deeper areas therefore information gained from EEGs is limited.
Poor spatial resolution (smallest feature that a scanner can detect) - cannot provide information on deeper regions of the brain so information is limited compared to fMRI.

Question 30

Strengths of ERPs

Answer 30

Good temporal resolution - takes readings every millisecond so there is an accurate measurement of activity.

Non-invasive - allows more patients to have an ERP which improves understanding of conditions.

Question 31

Limitations of ERPs

Answer 31

Poor spatial resolution - higher spatial resolution allows psychologists to discriminate between different brain regions with accuracy, unable to look at areas deeper in the brain.

Can only be interpreted by trained professionals, expensive, may minimise use of ERPs

Question 32

Strengths of fMRI

Answer 32

Non-invasive, no risk of physical harm

High spatial resolution (the smallest feature that a scanner can detect) - greater accuracy

objective - volume of blood can be measured showing fact rather than opinion.

Question 33

Limitations of fMRI

Answer 33

Poor temporal resolution (how quick it can detect changes) - unable to predict with a high degree of accuracy.

Small sample size in research - due to limited funding, difficult to generalise/low population validity.

Question 34

Localisation of function

Answer 34

Functions such as movement, speech and memory are performed in distinct regions of the brain.
The opposite view is that the brain acts holistically.

Question 35

Hemispheres of the brain

Answer 35

2 symmetrical halves - left and right.
Hemispheric lateralisation - functions are controlled by a particular hemisphere (language centres in left, visuospatial tasks best performed by right)

Each hemisphere of the brain controls the opposite side of the body - contralateral.

Question 36

Lobes of the brain

Answer 36

Cortex is subdivided into 4 lobes, each associated with different functions, damage to specific areas means that the functions associated with that area will also be affected.

Frontal lobe - motor area, brocas area
temporal lobe - auditory area, wernickes area
parietal lobe - somatosensory area
occipital lobe - visual area

Question 37

Frontal lobe

Answer 37

Motor area, controls voluntary movement.

Damage could cause loss of muscle function (fine movements or paralysis).
Effects are opposite side of the body to damage.

Question 38

Parietal lobe

Answer 38

Somatosensory area, detects sensations (touch, heat, pressure)

Damage could cause loss of sensation, neglect syndrome (reduces awareness of stimuli), agnosia (inability to identify objects and faces).
Effects are opposite side of the body to damage.

Question 39

Occipital lobe

Answer 39

Visual area, visual processing centre.

Damage could cause partial/complete blindness, cortical blindness (unable to see but to damage to structure of eye)
Effects are opposite side of the body to damage.

Question 40

Temporal lobe

Answer 40

Auditory area, receives and analyses speech bases information.

Damage could cause partial/complete hearing loss, cortical deafness (unable to hear but no damage to structure of the ear)

Question 41

Language centres of the brain

Answer 41

Language is restricted to the left.
Broca’s area and Wernicke’s area.

Question 42

Broca’s area

Answer 42

Left frontal lobe, responsible for speech production.

Damage results in Broca’s aphasia - patient understands but their own speech is slow and lacks fluency, difficulty with prepositions and conjunctions, demonstrated by Broca’s famous patient Tan.

Question 43

Wernicke’s area

Answer 43

Left temporal lobe, responsible for speech comprehension.

Damage results in Wernicke’s aphasia - severe difficulty in understanding speech, no problems producing speech, speech they produce is fluent but meaningless and often contains neologisms (nonsense words).

Question 44

Case study for localisation of the brain

Answer 44

Phineas Gage - suffered severe brain damage but only his personality was affected, motor functions, vision, hearing and speaking skills still intact. If the holistic theory was correct, he would have suffered with many more issues.

Question 45

Evidence for localisation theory

Answer 45

Case studies - Tan (aphasia - Broca’s area), Clive Wearing (amnesia - hippocampus), Phineas Gage (frontal lobe).
Strength - case studies suggest that these functions are localised in these areas. HOWEVER, these individuals experienced very specific brain damage, so it can be difficult to generalise to all cases of brain damage.

Brain scans - research, using fMRI, healthy participants show activation in Broca’s area during a reading out loud tasks and Wernicke’s area during listening task (Peterson et al 1988).
Strength - research is scientific and objective (unlike case studies), no bias when interpreting results - the results are what they are.

(A*) Neurosurgery - destroying or removing certain parts of the brain that are thought to contribute to psychological problems. For example, in OCD, cingulate gyrus appears to be more active. A bilateral cingulotomy to surgically interrupt the circuit, burn away the tissue using a gamma knife (radiation) or capsulotomy - probes into the top of the skull and heat the tips. Strength - Cosgrove and Rauch (2001) - cingulotomy was effective in 56% and capsulotomy in 67%. The surgery wouldn’t work if the theory was not true and no other functions are damaged. HOWEVER, not all patients are helped.

Question 46

Evidence against localisation theory

Answer 46

Language localisation research - suggesting language systems are more distributed - 2016 review found that only 2% of modern researchers think that language is completely controlled by Broca’s and Wernicke’s area. ‘Language streams’ identified in the right hemisphere. This contradicts the localisation theory, findings suggest that the correct approach in arguing for localised vs holistic is dependant on the function that we are considering, it is too simplistic to say one or the other.

Lashley’s rats research - trained rats to run a maze and then destroyed areas of their cortex (between 10% and 50%). It was found that it was the amount of brain destroyed not the specific part which led to worsening performance. Concluded that higher cognitive processes such as learning and memory are not localised, instead are distributed in a more holistically across the brain. There is an idea that the brain could compensate when damaged. HOWEVER, this research cannot be generalised to humans.

Question 47

Hemispheric lateralisation

Answer 47

Some physical and psychological functions are dominated by a particular hemisphere.

Question 48

Context for left and right brain

Answer 48

Right hemisphere can only produce rudimentary words and phrases, but it does not contribute emotional context. Suggestion that the left hemisphere is the analyser and the right hemisphere is the synthesiser, led people to the idea that there is ‘left brain’ people who are more scientific and ‘right brain’ people who are more creative.

HOWEVER, this idea is wrong, research suggests that people do not have a dominant side of their brain. Nielsen et al (2013) analysed brain scans from over 1000 people ages 7-29, no evidence for a positive side.

Question 49

Wiring in lateralisation

Answer 49

Many functions are not lateralised.

In the motor area, there is contralateral wiring - the right hemisphere controls movement on the left side of the body and vice versa.

Vision is both contralateral wiring and ipsilateral wiring (same side). Each eye has a left and right visual field, the left visual field of both eyes is connected to the right hemisphere and the right visual field is connected to the left hemisphere.

There is similar contralateral and ipsilateral wiring for auditory input

Question 50

Strength of theory of hemispheric lateralisation

Answer 50

Research evidence - Fink et al (1996), PET scans to identify which areas were active during a visual processing task.
One instruction - focus on fine details of a picture.
Findings - regions on left hemisphere were more active.
Second instruction - focus on whole photo.
Findings - regions of the right hemisphere were more active.
For visual processing, hemispheric lateralisation is a feature.

Research evidence to support the idea that lateralisation can change over time - Szaflarski et al (2006) found language became more lateralised to the left hemisphere with increasing age. HOWEVER, after the age of 25, lateralisation decreased with each decade of life.

Question 51

Limitation of the theory of hemispheric lateralisation

Answer 51

Idea of left and right brain people is wrong, research suggests that people do not have a dominant side of their brain. Nielsen et al (2013) analysed brain scans from over 1000 people ages 7-29, no evidence for a positive side.

Question 52

Split brain research (hemispheric lateralisation)

Answer 52

Corpus callosum connects the left and right hemispheres, a split brain operation severs this, usually done to reduce epilepsy.

Sperry (1968) studied 11 split brain patients and compared them to non-split brain patients.

1) picture/word shown to right visual field, info received by left hemisphere, participant could only describe what they had seen, this is because language is lateralised in the left hemisphere.

2) picture/word shown to left visual field, info received by right hemisphere, participants could not describe what they had seen, information received by the right hemisphere could not be controlled to the language centres in the left hemisphere.

3) picture/word shown to left visual field and asked to select a matching object, info received by right hemisphere, participants could not describe what they had seen but could select a matching object out of sight using their left hand, right hemisphere does have language comprehension but not speech or writing.

4) picture/word of an emotional object shown to left visual field, info received by right hemisphere, participant could not describe what they had seen but did have an emotional response, right hemisphere appears to experience its own emotional reactions.

Conclusion - certain functions are lateralised in the brain, this supports the view that the left hemisphere is verbal and the right hemisphere is emotional.

Question 53

Strengths of split brain research

Answer 53

Supporting research - Michael Gazzaniga (1989) - same findings as Sperry (could say words presented to right visual field, but not left), participants could draw (with left hand) the words presented to left visual field, shows that right hemisphere has language comprehension. This increases external reliability.

Question 54

Limitations of split brain research

Answer 54

Lack of control over variables as it was a quasi experiment (IV is naturally occurring), also split brain patients had severe epilepsy and the control group did not - this is a major cofounding variable because only one group had epilepsy, so it could be the condition explaining the split brain task results, not the actual split brain.

Oversimplified - the results are typical of right handed men

Question 55

Neural plasticity definition

Answer 55

Ability of the brain to change and adapt as a result of experience and new learning.

Question 56

What does neural plasticity do?

Answer 56

Plasticity increases the number of synaptic contacts from neuron to neuron, synapses help strengthen the connections between neurons. Number and strength of connections are linked to intelligence and other higher ability skills.

Plasticity is especially relevant during the early ‘critical years’, so during infancy, the brain experiences rapid growth in the number of synaptic connections. At birth, each neuron in cerebral cortex have 2500 synapses, by 3, number of synapses is 15000, 6x. (Gopnick et al (1999)).

Question 57

‘Use it or loose it’ (neural plasticity)

Answer 57

Very active synapses are likely to become stronger (long-term potentiation). If the neuron is stimulated repeatedly, a permeant neural change could potentially form, so we can physically consolidate a memory through repetition or exposure to experience.

Shown in research of taxi drivers, Maguire et al (2000) studied 16 London taxi drivers and found there was a high concentration of neurones (grey matter) in the posterior hippocampus and this was positively correlated with their time as a taxi driver. This area of the brain is involved in memory and spatial navigation, shows how the brain can permanently change in response to frequent exposure to a particular task.

Less active tend to become weaker (long-term depression).
As we mature connections that we do not use are deleted - neural pruning (Purcell and Zukerman (2011)).

Question 58

Limitations of neural plasticity (commentary point NOT evaluation).

Answer 58

Negative consequences - taking part in addictive behaviours, dopamine stimulates neurons in the dorsal striatum involved in forming habits can lead to tolerance and relapse in addicts. It can also cause changes in brain circuits which are important in deciding what we pay attention to.
Phantom limb syndrome, occurs in 80-100% of amputees and is often resistant to treatment. Thought to be due to cortical reorganisation of the somatosensory cortex, the brain remaps the part of the body’s sensory circuit to another part of the body, so the information is referred elsewhere. Plasticity is not always a good thing.

Question 59

Strengths of neural plasticity

Answer 59

Objective supporting research - Mechelli et al (2004), learning a second language increases the density of grey matter in the left parietal cortex, more fluency = more density, learnt at a younger age = more density.

Bezzola et al (2012) 40 hours of golf training increased motor cortex activity in new golfers ages 40-60.

Question 60

Functional recovery definition

Answer 60

Example of neural plasticity that can occur after trauma. Healthy brain areas may take over functions of those areas that are damaged, destroyed or missing. It may form new synaptic connections close to the areas of damage which enables functioning to continue.

Question 61

Ways functional recovery can occur

Answer 61

Axonal sprouting - undamaged axons grow new nerve endings to reconnect neurons whose links were injured or severed. Undamaged axons can connect with other undamaged nerve cells, forming new neural pathways.

Denervation super sensitivity - undamaged axons that do a similar job to those that are damaged become aroused to a higher level to compensate for those that are lost, however this can have negative consequences such as being overstimulated to pain

Recruitment of homologous areas on the opposite side of the brain.

Question 62

Strengths of functional recovery research

Answer 62

Real world applications - this process can occur quickly, but after weeks/months it can slow down, then rehabilitation therapy may be required to further recovery. Example: constraint-induced movement therapy to help patients who have had strokes. They repeatedly practice using the affected part of their body whole the unaffected arm is restrained, research has shown that this significantly increases function. This is due to recruitment of homologous areas on the opposite side of the brain.

Question 63

Limitations of functional recovery.

Answer 63

Factors such as age and level of education may impact recovery rates - Elbert et al (1994), capacity for neural reorganisation is much greater in children than in adults. Schneider et al (2014) found that 40% of people who achieved a disability-free recovery had more than 16 years of education compared to about 10% of those who had less than 12 years of education.

Small samples of patients or case studies of individual patients - cannot generalise findings because sample does not cover the population or because circumstances are too unique. Case studies could also create results that are biased from the researcher.

Question 64

Infradian rhythms

Answer 64

Menstrual cycle, takes longer than 24 hours to complete.

Question 65

The menstrual cycle (infradian rhythms)

Answer 65

Monthly changes in hormone levels. A typical cycle lasts around 28 days.

An egg is released, uterus is prepared for implantation if fertilisation happens.
1) menstrual stage - menstruation starts on day 1, lasts around 4 days.
2) follicular stage - uterus forms thick spongy lining ready for fertilised egg (day 4-14)
3) ovulation phase - egg released from ovary into uterine tube (day 14 = peak fertility)
4) luteal stage) uterus lining maintained for 14 more days (until day 28).
Follicle stimulating hormone (FSH) - makes follicle mature in ovary. Only made in the first 1/2 of cycle, then inhibited.
Luteinising hormone (LH) - stimulates ovulation, inhibits FSH, causes follicle to develop into corpus luteum (produces oestrogen and progesterone), controls growth of uterus lining.
Levels of these hormones fluctuate during the cycle.

It is an endogenous system but it can be influenced by exogenous zeitgebers

Question 66

Endogenous system

Answer 66

Controlled by internal factors

Question 67

Exogenous zeitgebers

Answer 67

Factors external to the body

Question 68

How can exogenous zeitgebers influence the menstrual cycle

Answer 68

During their cycle, women will secrete pheromones. These are secreted outside the body by an individual and received by a second individual of the same species.
Stern and McClintock (1998), showed how menstrual cycles may synchronise due to the influence of pheromones. Studied 29 women with irregular periods, samples of pheromones were gathered from 9 participants at different stages of their menstrual cycle. Women were asked to place a cotton pad under their armpit for at least 8 hours on each day of their cycle, cotton pads were treated with alcohol and frozen. On day 1, the remaining 20 women had day 1 of cycle pads rubbed on their upper lip, also on day 2, etc. 68% of women experienced changes to their own menstrual cycle which brought them closer to the cycle of their ‘odour donor’
Evolutionary advantage: if pregnancy is synchronised and the mother dies, there will be someone else who can feed the child (EEA)

It is also suggested that male pheromones may also be an exogenous factor that influence the menstrual cycle. McClintock (1971), reported that women who work with men have a much shorted menstrual cycle. Evolutionary advantage: women are mot fertile more often

Question 69

Seasonal affective disorder (infradian rhythms)

Answer 69

Type of infradian rhythm known as a circannual rhythm (repeating on a yearly cycle).
Also known as winter depression as symptoms are more apparent/severe in winter (persistent low mood, irritability, lethargic, loss of interest/pleasure in daily activities.

Evidence suggests that SAD is related to seasonal variations in the production of melatonin (mostly produced at night) which affects the production of serotonin which is implicated in depression.
Anti-depressants limit the reabsorption of serotonin so it increases.

Question 70

Limitations for synchronisation studies (infradian rhythms)

Answer 70

Extraneous and confounding variables - stress, diet, lifestyle, medication. Therefore findings are not always consistent, suggests that menstrual synchrony studies are flawed.
HOWEVER, some evidence of reliable findings, Russell et al (1980), applied pheromones (using cotton pad technique) to a group of sexually inactive women everyday for 5 months, there was also a control group. 4/5 in experimental group had menstrual cycles had synchronised.

Question 71

Strength of research into SAD (infradian rhythms)

Answer 71

Predictive validity - the theory can make accurate - predications about the occurrence of SAD. Terman (1988), nearly 10% of those living in New Hampshire (north) experienced SAD compared to only 2% in the southern state of Florida. Increases validity.

Real world applications - phototherapy. Strong light to reset the body’s internal clock and is found to reduce the effects of SAD in about 80% of people. Regarded as a safer treatment. Improves peoples quality of life. Increases validity.
HOWEVER, some people report headache and eye strain. Rohan et al (2009) compared people with SAD who were treated with phototherapy to a group who received CBT. Found relapse rate of 46% in phototherapy group and 27% for the CBT group.

Question 72

Ultradian rhythms

Answer 72

Sleep cycle, takes less than 24 hours to complete.

Question 73

The sleep cycle (ultradian rhythms)

Answer 73

5 stages, based on 90 minute cycles. Each stage is characterised by a different level of brain wave activity. Can be studied with an EEG.

1) light sleep (most people would deny being asleep), body relaxes, hr and temp fall, hypnogogic state may occur (vivid perceptions eg.falling perceptions) Characterised by alpha waves (mid frequency, short amplitude)

2) light sleep which you can easily be woken, body relaxes, hr, bp and temp fall, characterised by alpha waves (high frequency, short amplitude) and sleep spindles (brain activity following muscle twitching lasting approx 25 seconds)

3+4) deep sleep, hr, bp and temp fall to their lowest point and growth hormones are secreted, sleep walking, talking and night terrors can occur, characterised by delta waves (low frequency, high amplitude) also known as slow wave sleep.

5) paradoxial sleep - deepest sleep, but brain waves resemble being awake, hr, bp increase, breathing becomes faster and more irregular, rapid eye movement (REM sleep), body is paralysed (stops you acting out your dreams), hardest stage to wake someone up from, theta waves (closely resemble activity in the awake brain)

Question 74

Strength of research into sleep cycle (ultradian rhythms)

Answer 74

Improved understanding of age-related changes in sleep - Obayan et al (2004), meta-analysis of 65 studies of sleep patterns across the lifespan, participants age 5-102. Found decrease in SWS (stage 3+4), 24% of total sleep at age 5 and 9% of total sleep at age 70. Sleep has less and less of a restorative function which may help explain various issues in older age. This can encourage people to make use of relaxation and medication as they get older.

Research carried out in sleep labs using EEGs - high temporal resolution, can help in clinical diagnosis.

Question 75

Limitations of research into sleep cycles (ultradian rhythms)

Answer 75

Significant variation between people - Tucker et al (2007), found large difference between participants in terms of the duration of each sleep stage, particularly stages 3+4, these differences could be biologically determined. This makes it difficult to describe a ‘normal’ sleep cycle in any meaningful way.

Research carried out in sleep labs, using EEGs - cannot detect activity in deeper areas of the brain, poor spatial resolution, artificial environment.

Question 76

Circadian rhythms

Answer 76

Sleep-wake cycle, occurs over a 24 hour period.

Question 77

Sleep-wake cycles (circadian rhythms)

Answer 77

Tend to go to bed and wake up at approximately the same time everyday.

Governed by endogenous pacemaker - biological ‘clock’ called SCN (suprachiasmatic nucleus) within the hypothalamus, takes in all information about the amount and quality of light taken in by the eye.

Light can reset the SCN, suggesting daylight is an important exogenous zeitgeber in the sleep-wake cycle.

Question 78

Michael Siffre (circadian rhythms)

Answer 78

Spent nearly 7 months living in a cave with no exogenous zeitgebers. His circadian rhythm sleep-wake cycle was allowed to ‘free run’. At first it ranged from 25-32 hours, but eventually settled at 24.9 hours, not 24.
Similar results from Wever (1979), participants spend 4 weeks in a bunker, deprived of natural light, all but 1 participant settled into a 24.9 hour sleep-wake cycle.

Conclusions: our natural sleep-wake cycle is longer than 24 hours.
As his sleep-wake cycle was regularly 24.9 hours this is evidence of an endogenous pacemaker playing a role.
As we are in the real world we live to 24 hours suggesting that exogenous zeitgebers play a role.

Mustn’t overestimate the influence that exogenous zeitgebers have on out internal biological clock. Folkard et al (1985) studied 12 people who lived in a dark cave for 3 weeks, given a clock which researchers sped up over the study, the day was 22 hours long, not 24. 11 of participants were unable to adjust to a 22 hour day showing that we have a strong internal biological clock that cannot be easily overridden by zeitgebers.

Question 79

Strength of research into circadian rhythms

Answer 79

Practical applications.
Medical treatment - in chronotherapeutics - how medical treatments can be administered in a way which corresponds to someone’s biological treatments. Heart attacks are more likely in mornings, so taking medication last thing at night can reduce the risk of a heart attack (Bonten et al, 2015), increases effectiveness.

Shift work - desynchronisation, people working night shifts are more likely to have mental health issues and divorce. Most lorry accidents occur between 4 and 7 am, also shift workers are 3x more likely to develop heart disease. One suggestion is to rotate shifts with the clock, Czeisler et al (1982) tested this at a chemical plant in Utah and found that workers felt better and less tired, managers reported increased productivity and fewer errors. Real world health and economical productivity for shift workers.

Question 80

Limitations of research into sleep-wake cycle

Answer 80

Difficult to generalise - cave and bunker studies are based on very small samples. Other research suggests that sleep-wake cycles vary much more widely, Czeisler et al (1999) found individual differences in sleep-wake cycles varying from 13-65 hours. Duffy et al (2001) found some people are ‘larks’ and others are ‘owls’. Difficult to discuss anything more than averages meaning the practical applications that had been developed from such research may not be as useful.

Question 81

Endogenous pacemakers

Answer 81

Internal body clock.
Sleep-wake cycle involves both SCN and pineal gland.

1) optic chiasm takes in information about the amount of light and quality taken in by the eye.

2) Information travels along the optic nerve and into SCN

3) SCN passes information to pineal gland

4) Pineal gland secretes melatonin in relation to the amount of light there is. Negative correlation, decrease in light = increase in melatonin.

5) Melatonin induces sleep, levels rise from dusk and reach a critical level, making us sleepy.

Question 82

Animal studies on SCN (endogenous pacemaker)

Answer 82

We can generalise these findings to humans because there is similar mechanisms in the brain.
DeCoursey et al (2000) chipmunk study - 30 chipmunks had their SCN connections destroyed, returned to their natural environment and observed for 80 days, sleep-wake cycle disappeared, after 80 days a significant number had been killed as they were awake when predators were hunting.
Ralph et al (1990) hamster study - mutant hamsters with 20 hour sleep-wake cycles were bred, SCN cells from foetal tissue of the mutant hamsters were transplanted into the brains of normal hamsters, they took on the 20 hour sleep-wake cycle because the SCN controls it.

Question 83

Strength of animal studies on endogenous pacemakers

Answer 83

Reliable findings - Morgan (1995) removed the SCN from hamsters and found that the sleep-wake cycle disappears, then transplanted SCN from mutant hamsters brede to have shorter cycles and found that the sleep-wake cycle returns but was shorter
. Stephan and Zucker (1972) damaged SCN in rats and found that the sleep-wake cycle was disrupted.

Question 84

Limitations of research into endogenous pacemakers

Answer 84

Too simplistic - focussed on the SCN in the brain, but may ignore other biological clocks we have in other parts of the body (lungs, pancreas and skin). Although they are influenced by the SCN they also act independently from it. Ignoring other complex influences on circadian rhythms.

When studying the role of endogenous pacemakers we cannot study them in isolation - Siffre attempted to remove as many exogenous zeitgebers as possible there were still some, such as artificial light and these could have reset the biological clock. Pacemakers and zeitgebers do interact, so attempting to isolate each factor reduces validity.

Question 85

Exogenous zeitgebers

Answer 85

Light is the key zeitgeber in sleep-wake cycle.
Campbell and Murphy (1998) showed that light can be detected by skin receptors, woke up 15 participants ay various times and shone a light pad onto the back of their knees, this changed their usual sleep-wake cycle by up to 3 hours.

Light as the key zeitgeber is also supported by case studies.

Miles et al (1977) documented circadian rhythms of man who was blind since birth, he had a strong 24.9 hour sleep-wake cycle, struggled to set his body to 24 hour cycle so much that he had to use sedatives to sleep. Strong evidence that light is key because it was the only exogenous zeitgeber that he lacked.

Question 86

Evidence against light as the key zeitgeber

Answer 86

People in the Arctic circle live in a world of endless days in the summer and endless nights in the winter, yet they are able to maintain a fairly regular sleep-wake cycle. Could suggest sleep-wake cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light.

Or it could suggest that other exogenous zeitgebers have a part (social cues such as meal times). This can be seen in new born babies who are born with pretty random sleep-wake cycles surrounding parental schedules and mealtimes, circadian rhythms start to emerge at 6 weeks. This can also be seen in jetlag (internal body clock out of sync with external world), the most effective way to deal with this is to immediately adapt and ignore internal feelings.