biopsychology Flashcards
(129 cards)
1
Q
what is the nervous system divided into?
A
central nervous system and peripheral nervous system
2
Q
what is the job of the central nervous system?
A
- involves the brain and spinal cord and cerebral cortex
- is in charge of reflex actions
3
Q
what is the job of the central nervous system?
A
- involves the brain and spinal cord and cerebral cortex
- is in charge of reflex actions
- centre of conscious awareness
4
Q
what is the peripheral nervous system divided into?
A
somantic nervous system and autonomic nervous system
5
Q
what is the role of the somantic nervous system (voluntary)
A
- responsible for carrying sensori and motor information within spinal cord through nerves
- 31 pairs of spinal nerves
- 12 pairs of cranial nerves from brain
6
Q
what is the role of the autonomous nervous system (involuntary) ?
A
- governs vital functions in the body e.g breathing, heart rate, digestion
7
Q
what is the autonomous nervous system divided into?
A
sympathetic nervous system and the parasympathetic nervous system
8
Q
what is the role of the sympathetic nervous system (action and stress) ?
A
- preparation for fight or flight
- weak reaction
- uses as much energy as possible
9
Q
what is the role of the parasympathetic nervous system (calm and relaxation) ?
A
- maintains and conserves body energy functions
- strong reaction
10
Q
what are some sympathetic behaviours?
A
- dilating pupils
- accelerates heartbeat
- inhibits digestion
- relaxes bladder
11
Q
what are some parasympathetic behaviours?
A
- constricts pupils
-stimulates salivation - slows heartbeat
- contracts bladder
12
Q
what is the role of the sensory neurons?
A
- carries impulses from the PNS, receptors e.g pain receptors in the skin to the CNS. They have long dendrites and short axons. The cell body is in the middle of the axon
13
Q
what is the role of the relay neuron?
A
carries impulses from sensory neurons to motor neurons. They have short dendrites and short axons.
they make up 97% of all neurons
14
Q
what is the role of the motor neurons?
A
carries impulses from CNS to the effector e.g muscles or glands.
They have short dendrites and long axons
15
Q
what is the structure of a neuron?
A
- they vary in size from less than a mm up to a m
- the cell body (soma) includes a nucleus which holds all the genetic information for the body
- the dendrites carry nerve impulses away from neighboring neurons towards the cell body
- the axon carries impulses away from the cell body down the length of the neuron
- the axon is covered in a mylin sheath that protects the axon and speeds up chemical messages
- the myelin sheath is in gaps called “nodes of ranvier”
- t the end of the axon is the terminal buttons
16
Q
what is electrical transmission?
A
when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second, causing an action potential. This created an electrical impulse that travels down the axon towards the end of the neuron
17
Q
what is chemical transmission?
A
- neurons connect with each other through neural networks
- each neuron is separated from the next by a gap called the synapse
- signals within neurons are transmitted electrically
- however, signals between neurons are transmitted chemically across the synapse
-when electric impulses reach the presynaptic terminal, it triggers the release of neurotransmitters from the synaptic vessels
18
Q
what are neurotransmitters?
A
- they are chemicals that diffuse across the synapse to the next neurone
- they are taken up by the dendrites of the post synapitc neuron
- they are then put back into electrical impulses
- direction of travel is only one way
- neurotransmitters have been identified in the brain, spinal cord and some glands
19
Q
what is excitation?
A
when a neurotransmitter such as adrenaline, increases the positive charge of the postsynaptic neuron. This increases the likelihood that the postsynaptic neuron will pass on the electrical impulse
20
Q
what is inhibition?
A
what a neurotransmitter, such as serotonin, increases the negative charge of the postsynaptic neuron. This decreases the likelihood that the postsynaptic neuron will pass on the electrical impulse
21
Q
what is the effect of the hypothalamus?
A
stimulates and controls the release of hormones from the pituarity gland
22
Q
what hormone is released from the pituitary gland and what is the effect?
A
growth hormones are released and it controls the release of all the other hormones as well as producing growth hormones
23
Q
what hormone is released from the pineal gland and what is the effect?
A
melatonin is released and it releases higher levels when its dark and decreases production when it’s lighter
24
Q
what hormone is released from the thyroid gland and what is the effect?
A
thyroxine is released and it controls metabolism
25
what 2 hormones are released from the adrenal gland and what is the effect?
- adrenal cortex produces cortisol - increases in response to stress to regulate blood pressure, poor immune function
- adrenaline - releases in emergency situations
26
what 2 hormones are released from the ovaries and what is the effect?
oestrogen and progesterone are released and secrete hormones that mature the body for puberty e.g menstruation
27
what hormone is released from the testes and what is the effect?
testosterone secretes hormones that mature the body for puberty e.g characteristics like a deepened voice
28
what is the somatosensory cortex?
located in the parietal lobe: responds to heat, cold, touch, pair and our sense of body movement
29
what is the motor cortex?
in the frontal lobe: responsible for controlling voluntary movements. both hemispheres have one - controlling muscles- damage can result in impaired movement
30
what is the occipital lobe?
primary function is vision
31
what is the temporal lobe?
auditory ability and memory
32
what is broca's area?
on the frontal lobe of the left hemisphere and is responsible for thought into speech
33
what is Wernicke's area?
located on temporal lobe and understanding and producing speech
34
what is Localisation of Function?
the theory that different areas of the brain are responsible for specific behaviours, processes, or activities - follows the idea that if a certain part of the brain is affected - only the function of that one area will be affected
35
what is the structure of the hemispheres of the brain?
-Divided into 2 symmetrical halves (left and right hemisphere)
-Some physical and psychological functions are dominated by one in particular (lateralisation)
-Activity on left side of body is controlled by right hemisphere and vice versa
36
strength of localisation - links to mental disorders
- Darin Dougherty et al (2002) reported on 44 people with OCD who had undergone a cingulotomy
- a post-surgery follow up after 32 weeks showed that 30% of the participants had success and 14% had a partial response
37
strength of localisation - brain scans
- steven peterson et al (1988) used brain scans to look at activity in the Wernicke's area during listening tasks and Broca's area during reading tasks
- this provides evidence for localisation
38
weakness of localisation - Language Localisation Questioned
- Language may not be localised to just Broca and Wernicke's areas
-Advances in brain imaging techniques, like fMRI, mean neural processes in the brain can be studied with more clarity than before
-It seems language function is distributed more holistically - so-called language streams have been identified across the cortex
-Rather than being confined to a few key areas, language may be organised more holistically in the brain, contradicting localisation theory
39
strength of localisation - phineas cage
-Most of his left frontal lobe damaged in accident but he survived the damage but he turned from someone who was calm to quick-tempered and rude
-Suggested the frontal lobe may be responsible for regulating mood
-Unique cases of neurological damage like this tend to support localisation theory but it is difficult to make meaningful generalisations from the findings of a single individual and conclusions depend on the subjective interpretation of the researcher
40
what is lateralisation?
the two hemispheres work separately and have their own separate functions
41
how is lateralisation different to localisation?
- localization is how much any one function is located in a specific area of the brain
-lateralisation is how much anyone function is located more in one hemisphere than the other
42
what are some examples of lateralisation?
- brain damaged individuals
- non brain damaged individuals
- methods such as the WADA test
43
what is the corpus callosum?
a bundle of nerves that allows the hemispheres to send information to the other
44
what is the split-brain research for lateralisation?
A series of studies which began in the 1960s (and are still ongoing) involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain to reduce severity of their epilepsy. This allowed researchers to investigate the extent to which brain function is lateralised
45
what is a Commissurotomy ?
Severing of the corpus callosum that links the two hemispheres
46
Evaluation of research using split brain patients
-Its highly controlled lab research so lacks ecological validity
-Limited sample size
-Participants had epilepsy (lack of generalisability)
47
Left Hemisphere Functions
- Language, speech and comprehension
- Recognition of words, letters and numbers
- Analysis and calculations
- Time and sequencing
47
Left Hemisphere Functions
- Language, speech and comprehension
- Recognition of words, letters and numbers
- Analysis and calculations
- Time and sequencing
48
Right Hemisphere Functions
- Recognition of faces, places and objects
- Context / perception
- Spatial ability
- Creativity
49
Sperry and Gazzaniga (1967)
-11 patients whose corpus callosum had been severed
-They were presented with images to either the left or right visual field
-A range of tasks were used and patients had to respond with either their left (right hemisphere) or right hand (left hemisphere)
-Found the patient could say what they saw in their right visual field, because this hemisphere is responsible for language but not in their left visual field, because this hemisphere cannot process language
-Patient could draw this image with their left hand - did not require language
50
Strength of lateralisation:
Multitasking
-Increases neural processing capacity (ability to multitask)
-Rogers et al (2004) found in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform 2 tasks simultaneously (finding food and being vigilant for predators)
-Using one hemisphere to complete tasks leaves the other hemisphere free to engage in other functions
-Provides evidence for the advantages of brain lateralisation and demonstrates how it can enhance brain activity in cognitive tasks
51
Limitation of split brain research:
Small Sample
Split brain procedure is rarely carried out so patients are difficult to come by
-Research is really a collection of case studies that take an idiographic approach, although this provides rich and interesting information, it is not easily generalised
52
Limitation:
Language may not be restricted to left hemisphere
-Turk et al (2002) found a patient who suffered damage to the left hemisphere but developed a capacity to speak within the right hemisphere
-Suggests lateralisation is not fixed and the brain can adapt following damage to certain areas
53
what is brain plasticity?
The brain's tendency to change and adapt as a result of experience and new learning - generally involves the growth of new connections
53
what is brain plasticity?
The brain's tendency to change and adapt as a result of experience and new learning - generally involves the growth of new connections
54
what is synaptic pruning?
a prcoess used to enhance the connections in the brain
55
what is Structural Plasticity
The brain's ability to change its physical structure in response to learning
56
what is Functional Plasticity
The brain's ability to move functions from a damaged area of the brain to other undamaged areas
57
what happens in the brain during functional recovery?
- new synaptic connections are formed close to the area of damage
- secondary neural pathways that would no usually be used are "activated"
58
what is axon sprouting?
the growth of new nerve endings which connect to undamaged nerve cells to form new neural pathways
59
what is denervation super sensitivity?
this occurs when axons that do a similar job become aroused to a higher level to compensate for lost ones. However, it can lead to oversensitivity, especially when it comes to pain
60
recruitment of homologous areas
Areas on the other side of the brain take over tasks from the damaged area and allow specific functions to take place
61
Kuhn (2014) - Research into Plasticity
- Participants played Super Mario for 30 minutes per day over 2 months
- Compared their brain development to a control group (didn't play video games over 2 month period)
- Found significant differences in the grey matter of the video gaming participants, particularly in the cortex, hippocampus and cerebellum (co-ordination and movement)
62
Davidson et al (2004) - Research into Plasticity
- Studied Tibetan monks and compared them to non-meditation controls
- Each group meditated for a short time and were fitted with electrical sensors to detect brain activity
- Monk group showed higher levels of gamma wave activity (helps to co-ordinate neuron activity)
63
Maguire et al (2000) - Research into Plasticity
- Studied brains of London taxi drivers, investigating whether or not the hippocampus plays a role in human spatial memory
- Range of age and experience
- Matched pairs design: participants were age and gender matched with a control group
- 2 types of MRI scanning used to asses how the brains of the taxi drivers differed to the control group
- Found significantly more volume of grey matter in the posterior hippocampus than in the matched control group
64
evaluation limitation brain plasticicty - negative plasticity
- can have negative behavioral effects
e.g dementia, the brain adaption to prolonged drug use and the fact that amputees suffer with phantom leg syndrome
65
evaluation strength - age and plasticity
- Brain plasticity may be a lifelong ability
- Bezzola et al (2012) show that 40 hours of golf training produces changes in neural representation in 40-60 year olds
66
evaluation strength brain plasticity - real world application
- used in rehabilitation
- things like understanding axon growth has encouraged new forms of therapy.g constraint-induced therapy in patients who have had a stroke
- allows professionals to see where intervention is needed
67
evaluation limitation brain plasticity - cognitive research
- level of education may affect recovery rates
- Schneider et al (2014) found that the more time that someone spends in education, the more likely they were to have disability-free recovery
- this implies that those with brain damage who had insufficient DFR are less likely to achieve a full recovery
68
what is functional magnetic resonance imaging (FMRI)
- works by detecting the changes in both blood oxygenation and flow that occur as activity in a specific part of the brain
- when a part of the brain is more active, it consumes more energy and oxygen, blood flow increases (hemodynamic response)
- it produces three dimensional images (activation maps) that show which parts of the brain are involved in particular mental processes
69
benefits of fMRI
- it does not rely on the use of radiation
-virtually risk free, non invasive and straightforward to use
-high resolution images
70
cons of fMRI
- expensive
-poor temporal resolution (how quickly the scanner can detect changes)
- 5 second lag means that we may not see real-time activity
71
what is electroencephalogram (EEG)
- measures electrical activity in the brain with electrodes that are fixed on the individual's brain with a skull cap
- the scan recording represents brain wave patters that are generated by neurons
- often used by clinicians to look at irregular activity and detect neurological abnormalities
72
benefits of EEGs
- useful in the study of sleep
- useful in diagnosing things like epilepsy
- high temporal resolution
- real world usefulness
73
cons of EEGs
- generalised nature of the information given
- not good at pinpointing the source of neural activity
- doesn't allow researchers to distinguish between activity in different but adjacent regions
74
what are event-related potentials
- EEGs are often too general
- short segments of EEG data brain waves that are time-locked to particular events
- often linked to cognitive processes like attention and perception
75
benefits of ERP
- more specific to EEGs
- good temporal resolution
76
cons of ERP
- lack of standardisation
- extraneous variables can affect the data
77
what are post mortem exams
- analysis of a person's brain after death
- usually done on people who have had a rare disorder or experienced strange cognitive processed
- areas of the brain that are damaged are compared with a neurotypical brain
78
benefits of post mortem exams
-vital for understanding the early key processes of the brain
- both Broca and Wernicke relied on this for their research
- provide key information
79
cons of post mortem exams
- damage to the brain may be linked to different/ unrelated trauma or decay
- it raises ethical questions in terms of consent from the participant
80
what is a biological rhythm?
a distinct pattern of changes in body activity that conform to cyclical time periods, They can be influenced by internal or external factors
81
what is a circadian rhythm?
a type of biological rhythm that operates along a 24 hour cycle. This regulates a number of bodily processes such as the sleep / wake cycle and core body temperature
82
what is a ultradian rhythm?
biological rhythms that occur more than one cycle in 24 hours
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what is an infradian rhythm?
biological rhythms that occur less than one cycle in 24 hours
84
what is an endogenous pacemaker?
internal body clocks that regulate biological rhythms
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what is an exogenous zeitgebers?
external cues that influence our biological rhythms
86
what does the circadian clock regulate?
- sleeping and feeding patterns
- alertness
- core body temperature
- brain wave activity
- hormone production
87
what does the circadian clock regulate?
- sleeping and feeding patterns
- alertness
- core body temperature
- brain wave activity
- hormone production
88
what hormones are affected by the circadian rhythm?
- melatonin and cortisol
89
where is the circadian rhythm located?
the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain, one in each hemisphere
90
what times do biological functions usually work?
- core temperature reaches its minimum 4:30 - 5am
- melatonin is completely absent during the day, begins being produced around 9pm and stops around 8am
- the deepest part of sleep is usually around 2-3am
- people often experience a "post-lunch dip" around 2-3pm (12 hours later)
91
what was the aim of siffre's cave study?
to observe the rhythms of a brain without any external factors
92
what was the procedure of siffre's cave study?
- He settled into a sleep-wake cycle of around 24 hours and 30 minutes.
- He went into the cave on 16 July 1962 and came out of the cave on 14 September 1962. However, Siffre thought the day he came out of the cave was the 20 of August
- The only participant in the experiment was Siffre himself. He spent 179 days and nights in an underground cave. He had no lights, clocks or radios to give him any indication of what time it was
- His only link to the outside world was a telephone where he could keep in touch and was also monitored by video camera and by wires attached to his body that monitored how he was functioning.
93
what were the findings of siffre's cave study?
- At first, Siffre’s sleep-wake patterns were very erratic
- After a while, they settled into a 25-hour pattern rather than 24 hours, which is the time a human considers to be a full day and therefore how long a sleep-wake cycle should last
94
what was the conclusions of siffre's cave study?
- Siffre thought astronauts could manage their biological rhythm without exogenous zeitgebers; however, they would need companionship as the isolation would not be manageable.
- Siffre concluded that time is not something humans could work with and understand without any external environmental cues.
95
what were the strengths of siffre's cave study?
- The study produced a lot of quantitative and qualitative data.
- The study was done over a long time, six months, which allowed Siffre to investigate his sleep-wake cycle and show how irregular it became.
95
what were the strengths of siffre's cave study?
- The study produced a lot of quantitative and qualitative data.
- The study was done over a long time, six months, which allowed Siffre to investigate his sleep-wake cycle and show how irregular it became.
96
what were the weaknesses of siffre's cave study?
- When Siffre woke up, strong lights were put on, and when he went to sleep, they were turned off. The lights could have acted as an external cue, which affects the study's internal validity.
- Siffre was the only participant in the study, so it is hard to generalise his findings, such as how he did to astronauts.
97
Aschoff and Wever (1976)
- convinced a group of participants to spend 4 weeks in WW2 bunker, deprived of sunlight
- all but one of the participants displayed a circadian rhythm of between 24-25 hours (29 of the one participant)
98
Folkard et al (1985)
- studied a group of 12 people who agreed to live in a dark cave fro 3 weeks, retiring to bed when the clock says 11:45pm and waking when the clock says 7:45am
- over the course of the study, the researchers gradually began to speed up the clock, so a 24 hour day became 22 hours
- only one of the participants was able to comfortably adjust to the new regime
-This suggest that biological clocks overturn external factors
99
strenght of circadian rhythm - shift work
- on strength of circadian rhythms is that it provides and understanding of the consequences when the rhythm is disrupted
- research had shown that night workers that work on a shift pattern make more mistakes around 6 in the morning
- there is also evidence to suggest that there is a relationship between shift work and poor health - shift workers are 3 times more likely develop heart disease
- this suggests that the sleep / wake cycle has more real world applications
100
strength of circadian rhythm - medical treatment
- another strength is that they have been used to improve medical treatments
- using them in coordination with heart rate, hormones and digestion
- treatments can be administered at the times when they will be most effective
- this shows the real, physical benefits that circadian rhythms can have
101
limitation of circadian rhythms - individual differences
- one limitation is that the idea does not account for individual differences and is difficult to generalize
- studies like Siffre use a very small sample and it is difficult to generalize them to a wider population where there may be individual differences that affect the results
102
how does the menstrual cycle link to infradian rhythm?
- governed by monthly changes in hormones
- a typical cycle last 28 days
- during each cycle, rising levels of oestrogen causes the ovary to develop and release an egg
- after ovulation, the hormone progesterone helps the womb lining to grow thicker, preparing the womb for pregnancy
- if pregnancy doesn't occur, the egg is absorbed back into the body and the womb lining comes away and leaves the body
103
evidence that the menstrual cycle may be influenced by exogenous factors
-Stern and McClintock (1998)
- studies 29 women with a history of irregular periods
- samples of pheromones were collected from 9 of the women's armpits at different stages of their periods
- found that 68% of women experienced changes in their cycle
Russel et al (1980)
- found that female menstrual cycles became synchronised with other females through odour exposure. In one study, sweat samples form one group of women were rubbed onto the upper lip of the other. Despite the two groups being separate, their menstrual cycles synched
104
how does Seasonal affective disorder (SAD) link to infradian rhythms?
- has a subsection called the "circannual rhythm"
- can be classed as circadian rhythm and may be caused by the disruption to the sleep / wake cycle
- hypothesized that melatonin is involved
- during the night, the pineal gland secreted melatonin until dawn
- however, during the winter, the lack of light slows the secretion process
- this is thought to have a knock on process for serotonin
105
what happens in stage 1 of sleep?
light sleep, muscle activity slows, occasional muscle twitching, short brain waves
106
what happens in stage 2 of sleep?
breathing pattern and heart rate slows, slight decrease in body temperature, short brain waves and occasional large brain waves
107
what happens in stage 3 of sleep?
deep sleep and brain begins to generate slow delta waves
108
what happens in stage 4 of sleep?
very deep sleep, rhythmic breathing, limited muscle activity, brain produces delta waves
108
what happens in stage 4 of sleep?
very deep sleep, rhythmic breathing, limited muscle activity, brain produces delta waves
109
what happens in stage 5 of sleep?
rapid eye movement, brain waves speed up, dreaming occurs, muscles relax and heart rate increases, breathing is rapid and shallow
110
strength of synchronised studies - explained by natural selection
- for our distant ancestors, it may have been beneficial to synchronise menstrual cycles and births as it allowed the children of mothers who had died in childbirth to get access to breast milk
111
limitation of synchronised studies - external factors
- there are many factors that can affect a menstrual cycle e.g stress, change in diet
- these may act as confounding variables which means that any supposed pattern of synchronised is no more than would have been expected to occur by chance
111
limitation of synchronised studies - methodological shortcomings
- there are many factors that can affect a menstrual cycle e.g stress, change in diet
- these may act as confounding variables which means that any supposed pattern of synchronised is no more than would have been expected to occur by chance
112
strength of research into ultradian rhythm- proved changes in age related studies
- studies have shown that deep sleep reduces with ages
- in order to increase this, relation and meditation may be used
113
limitation of ultradian rhythms - individual differences
- doesn't account for individual differences
- there is no technical thing as "normal sleep"
114
what is the SCN and where is it located?
- a tiny bunch of nerves located behind the eye in the hypothalamus in each hemisphere
- one of the primary endogenous pacemakers and detects light even when the eyes are closed
- allows the biological clock to adjust changing patterns of daylight when we are asleep
115
how does the pineal gland and production of melatonin work?
- when light is sense, the pineal gland causes melatonin to inhibit
- when light levels fall, melatonin increases
- this induces sleep by inhibiting the brain mechanisms that promote the awake state
- the SCN is connected to the pineal gland via a pathways of neurons
116
Miles et al (1977)
- case study of a man blind from birth and had a circadian rhythm of 24.9 hours
- he had a problem keeping in tune with a rhythm of 24 hours even with the use of stimulates in the morning and sedatives at night
- although light "sets" the clock, bio rhythms can continue when even zeitgebers such as light are not present, by the light directly falling on the retina of the eye, affecting the SCN means this cycle can be perfectly synchronised with light and dark phases
117
Patricia DeCoursey et al (2000)
- destroyed the SCN connections in the brains of 30 chimpunks and then were returned to the wild and observed for 80 days
the sleep / wake cycle of the chipmunks disappeared
- by the end of the study, a significant portion of them had been killed by predators ( they were, active and vulnerable to attack)
118
Martin Ralph et al (1990)
- bred "mutant" hamsters with a 20 hour sleep/ wake cycle
- when SCN cells from the foetal issue of the mutant hamsters were transplanted into the brain of normal hamsters, the cycle of the second group defaulted to 20 hours
119
how does light act as a exogenous zeitgeber?
- has an indirect effect on key processes such as hormone secretion and blood circulation
- Scott Campbell and Patricia Murphy (1998) demonstrated that light may be detected by skin receptor sites on the body even when not detected by the eyes
- 15 participants were woken at various times and a light pad at the back of their knees
- the researchers managed to deviation of sleep/ wake cycle of up to 3 hours
- this suggests that light is a powerful exogenous zeitgeber that doesn't necessarily need to have light on the eyes
120
how do social cues act as exogenous zeitgebers?
- circadian rhythms begins at about 16 weeks old, until then, it is pretty random
- by 16 weeks, babies begin to pick up on routines like meal time and bed times
- research on jet lag has found that adapting to local times in terms of sleeping and eating helps you adjust better to the timezone
121
limitation of SCN - obscure to other body clocks
- research has revealed that there are numerous circadian rhythm in many organs and cells in the body
- these peripheral oscillators are found in the organs
- they are influenced by the actions of the SCN but also act independently
Francesca et al (2000)
- demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the liver by up by 12 hours while leaving the rhythm of the SCN unaffected
- this suggests that other complex influence on the sleep / wake cycle
122
limitation of endogenous pacemaker - cannot be studied in isolation
- total isolation studies such as Siffre's cave study are extremely rare
- siffre's cave study used artifical light which could reset his biological clock everytime he turned on the light
- in everyday life, pacemakers and zeitgebers interact, and it may make little separate the two for research purpose
- this suggests that the more researchers attempt to isolate the influence of internal pacemakers, the lowers the validity of the research
123
limitation of exogenous zeitgebers - does not have the same effect in all environments
- those who live in in differnent light levels have a similar sleep / wake cycles
- this suggests that the sleep / wake cycle is primarily based on endogenous pacemakers
124
limitation of exogenous zeitgebers - evidnece challenges the role
Laughton Miles et al (1977)
- recounted a study of a young man, blind at birth, who had an abnormal circadian rhythm 24.9 hours
- despite exposure to social cues, e.g meal times, his sleep / wake cycle could not be adjusted
- this suggests that social do not have an effect
