Biopsychology Flashcards
1
Q
What are neurons?
A
The basic building blocks of the nervous system - they process and transmit messages through electrical and chemical signals
2
Q
What are the different functions of the neuron?
A
- Dendrites: branchlike structures that receive signals from other neurons or sensory receptor cells
- Axon: carries impulses away from cell body down length of neuron
- Myelin sheath: insulates the axon so that the electrical impulses travel faster along the axon
- Terminal button: connects the neuron to other neurons using synaptic transmission
- Nodes of ranvier: segments the myelin sheath, speeds up electrical transmission by forcing impulses to jump across the gaps
3
Q
What is action potential?
A
- A tiny electrical impulse that is triggered by a change in the electrical ‘potential’ of the neuron itself
- The inside of the neuron goes from being negatively charged to positively charged
4
Q
What is the structure and function of the 3 types of neurons?
A
- Motor: found in the CNS, and connects CNS to effectors like muscles and glands, to control muscle movements - short dendrites & long axons
- Sensory: found in receptors cells (e.g. skin) + carry nerve impulses from PNS -> spinal cord & brain - when these impulses reach the brain -> translated into ‘sensations’ (e.g. touch) - longer dendrites & short axons
- Relay: found in between sensory input and motor response + connect sensory neurons to motor or other relay neurons - short dendrites & short axons
5
Q
What is synaptic transmission?
A
The process by which one neuron communicates with another
6
Q
What are the stages of synaptic transmission?
A
1) An electrical signal called an action potential arrives at the presynaptic neuron
2) This stimulates vesicles containing neurotransmitters to move down and bind to the wall of the presynaptic neuron
3) Neurotransmitters are released from the vesicles into the synaptic cleft
4) Neurotransmitters are received by receptors on the post-synaptic receptors via a lock and key mechanism
7
Q
What are the functions of the 2 elements of the CNS?
A
- Brain: centre of awareness - divided into 2 hemispheres - outer layer is what distinguishes us from animals (cerebral cortex)
- Spinal cord: an extension of the brain - transports messages to and from the brain to the PNS - responsible for reflexes
8
Q
What are the functions of the 2 subsystems of the PNS?
A
- Autonomic nervous system: responsible for vital functions such as heart rate, breathing, digestion
- Somatic nervous system: receives info from the senses and transmits it to the CNS - also transmits info from CNS to direct muscle movement
9
Q
What is the role of the endocrine system?
A
Works alongside the nervous system to regulate bodily functions through the release of hormones
10
Q
What are hormones?
A
A chemical secreted by the endocrine glands into the bloodstream which then distributes it around the body
11
Q
What are the differences between the endocrine and nervous system?
A
- Endocrine: chemical messengers, long-lasting effects, takes longer, more permanent and wide
- Nervous: electrical impulses, short-lived effects, quick, localised
12
Q
Explain the process of the fight or flight response?
A
- The endocrine and ANS work in parallel e.g. during a parallel event
- When a stressor is perceived the hypothalamus triggers the sympathetic nervous system and the ANS changes from its usual resting state (the parasympathetic state)
- Activates adrenal medulla to release adrenaline into the bloodstream
- Binds to target cells -> bodily reactions - physical arousal needed for fight/flight
13
Q
What are the differences between the sympathetic and parasympathetic state?
A
- Sympathetic state- increased heart rate, increased breathing rate, dilates pupils, inhibits digestion etc
- Parasympathetic state- decreases heart rate, decreases breathing rate, constricts pupils, stimulates digestion etc
14
Q
What is localisation of function in the brain?
A
Different parts of the brain are involved in different tasks and are associated to different behaviours
15
Q
What is the opposite of localisation of function?
A
Holism - the whole brain is implicated in behaviours and functions
16
Q
What is the structure of the brain?
A
- Two symmetrical hemispheres
- Psychological & physical functions are controlled/dominated by a particular hemisphere
- Left-side of body -> controlled by right hemisphere and vice versa
- Outer layer - cerebral cortex - separates us from animals (more developed)
17
Q
What are the 4 main brain centres in the cerebral cortex?
A
- Motor area (back of frontal lobe) - controls voluntary movement on the opposite side of body
- Somatosensory cortex (front of parietal lobe) - where information from senses (skin) is represented
- Visual cortex (occipital lobe) - each eye sends info from left and right visual fields to left and right cortex (LVF-> right half of both your eyes + vice versa)
- Auditory area (temporal lobe) - analyses speech based info - damage = partial hearing loss
18
Q
Where are Wernicke’s area and Broca’s area located and what are their functions
A
Broca’s area:
- Left frontal lobe
- Speech production
- Broca’s aphasia -> slow laborious speech
Wernicke’s area:
- Left temporal lobe
- Speech comprehension
- Wernicke’s aphasia -> speech production is fine but understanding is poor
19
Q
What are the strengths of localisation theory? (A03)
A
- Brain scan evidence: support for localisation of language/memory - Petersen et al used brain scans to show Wernicke’s area was active in a listening task, broca’s in reading (different roles) + Tulving et al’s LTM study showed semantic & episodic reside in different parts of prefrontal -> research conducted with sophisticated & objective methods to measure brain activity
- Neurosurgery: lobotomies used to be common (surgically removing parts of the frontal lobe) - controversially still used - Dougherty et al -> 44pts with OCD underwent a cingulotomy - 32wk follow up, 1/3 showed a successful response
- Case-study evidence: Gage was caught in an explosion where a meter length pole was hurled through his head, tearing most of his frontal lobe - became short-tempered & aggressive -> suggests frontal is responsible for mood regulation
20
Q
What are the weaknesses of localisation theory?
A
- Gender differences found within research of cortical specialisation - Harasty et al found women have larger Broca’s & Wernicke’s than men - this difference makes it difficult to map specific areas (beta bias)
- Reductionist: simplifies complex brain processes by focusing on specific areas, ignoring the interconnectedness of brain regions, e.g. cognitive tasks like problem-solving or memory involve networks of areas working together rather than isolated regions
- Case study limitations: evidence from case studies, such as Phineas Gage, often involves small, unique samples with no control group, limiting generalizability + these studies rely on retrospective data - may not provide an accurate picture of brain functions prior to the damage
21
Q
What is hemispheric lateralisation?
A
The idea that both hemispheres are functionally different & that certain mental processes & behaviors are mainly controlled by one hemisphere rather than the other
22
Q
What was Sperry’s split-brain research?
A
- A study on a group pf individuals who had undergone a comissurotomy (severing the corpus callosum to control seizures)
- Sperry could see the extent to which 2 hemispheres were specialised for certain functions
23
Q
What was the procedure of Sperry’s split-brain research?
A
- An image /word was projected to a patient’s RVF (processed by LH) & the same/different image could be projected to LVF
- Normal brain - corpus callosum would share info between hemispheres -> info couldn’t be conveyed to another in patients
24
Q
What were the findings of Sperry’s split brain research?
A
- Describing what you see: if image/word was flashed up in RVF, patient could say what they saw but if flashed into LVF patient reported seeing nothing + couldn’t say what they saw
- Recognition by touch: if image flashed into RVF, could say what they saw, if flashed into LVF they couldn’t say what they saw but could blindly pick an item from a bag matching what they saw with left hand
- Composite words: one flashed in LVF, other in RVF e.g. keyring -> patients could say the word ring (it’s in RVF) and used left hand to draw a key + could say key after drawing one
25
What is a strength of split brain research? (A03)
- Research support: Gazziniga showed split-brain patients performed better than connected control on certain tasks - e.g. they were faster at identifying the odd one out in an array of similar objects than control -> in normal brains, the LH's better cognitive strategies are watered down by inferior RH (Kingston et al) -> left & right brain are distinct
26
What is a weakness of split-brain research? (A03)
- Generalisation issues: hard to establish cause & effect in Sperry's research - the behaviour of Sperry's split-brain patients was compared to a neurotypical control group (none had epilepsy was the issue - confounding variable) -> any differences observed between the 2 groups may be the result of epilepsy not split-brain -> some of the unique features of split-brain ppts cognitive abilities' may be due to their epilepsy
- Rare procedure: only carried out when all treatment options have been exhausted - only invloves study of a small group of abnormal individuals
27
What is a strength of hemispheric lateralisation? (A03)
- Research support for lateralisation in connected brains: Fink et al used PET scans to identify which brain areas were active during a visual processing task - connected brain ppts were asked to attend to global elements of an image and regions of their RH were more active - when asked to focus in on finer details, specific areas of the LH dominated -> for visual processing, lateralisation is a feature of connected brains
28
What is a weakness of hemispheric lateralisation? (A03)
- One brain: the idea of the LH as analyser & RH as syntheiser may be wrong - research suggests people don't have a dominant side of the brain that creates a different personality - Nielsen et al analysed brain scans from over 1000 people ages 7-29 + found people used certain hemispheres for certain tasks, no evidence of a dominant side -> notion of left/right-brained is people wrong
- Lack of ecological validity: tasks used (e.g. visual stimuli presented to one visual field) are artificial & don't reflect real-life cognitive processes, reducing how well findings apply outside the lab
29
What is plasticity?
This describes the brain's tendency to change and adapt as a result of experience and new learning - generally involves the growth of new connections
30
What is functional recovery?
A form of plasticity - following damage through trauma, the brain's ability to redistribute or transfer functions usually performed by a damaged area to other undamaged areas
31
What is synaptic pruning?
As we age, rarely used connections are deleted - frequently used connections are strengthened
32
Describe the functions of the following main brain areas:
- Hippocampus?
- Grey matter?
- Posterior?
- Parietal cortex?
- Hippocampus: helps convert STMs into LTMs & is also involved in spatial navigation, decision-making & emotion
- Grey matter: key part of the CNS & is responsible for many functions of the brain - movement, emotions, memory learning, reasoning
- Posterior: a posterior hippocampus is more involved in detail memories
- Parietal cortex: movement, spatial processing, sensation etc
33
What is the corpus callosum?
Fibers branching the two hemispheres together
34
What is the optic chiasm?
The left visual field is connected to the RH and the right visual field is connected to the LH
35
What research did Maguire conduct into plasticity?
- Investigated the brains of London taxi drivers & found significantly more volume of grey matter in their posterior hippocampus than matched control
- Found that the learning experience ('The Knowledge') alters the structure of the brain
- Also found that the longer the taxi driver has been in the role, the stronger the structural difference/ positive correlation
36
What research did Draganski conduct into plasiticity?
- Imaged the brains of medical students 3 months before and after their final exams
- Learning-induced changes were seen to have occurred in posterior hippocampus & parietal cortex -> presumably as a result of learning
37
What happens during functional brain recovery?
- The brain is able to rewire & recognise itself by forming new synaptic connections close to the area of damage
- Secondary neural pathways establish causing pathways to be activated by several structural changes:
-> Axonal sprouting
-> Denervation super sensitivity
-> Recruitment of homologous areas on opposite sides of the brain
38
What are the 3 structural changes that support brain recovery?
- Axonal sprouting: the growth of new nerve endings that connects with other undamaged nerve cells
- Denervation super sensitivity: occurs when axons doing similar jobs become aroused to a higher level to compensate for ones lost
- Recruitment of homologous areas on opposite sides of the brain: specific tasks can still be performed
39
What are the strengths of research into plasticity? (A03)
- Brain plasticity may be a life-long ability: in general plasticity reduces with age but Bezzola et al showed how 40hrs of golf training produced changes in the neural representations of movement in ppts aged 40-60 -> using fMRI researchers observed increased motor cortex activity in novice golfer than control (more efficient) -> neural plasticity can continue throughout a lifespan
- Research support for seasonal plasticity in response to environmental changes: e.g. for the SCN (suprachiasmatic nucleus) which regulates sleep - Tramontin & Brenowitz found evidence that this particular brain structure shrinks in all animals in spring & expands throughout autumn
40
What are the weaknesses of research into plasticity? (A03)
- Plasticity may have negative behavioural consequences: evidence has shown the brain's adaptation to prolonged drug use -> poorer cognitive functioning in later life + increased dementia risk (Medina et al) - 60-80% of amputees have been known to develop phantom limb & these sensations are usually unpleasant + thought to result from cortical reorganisation in the somatosensory that occurs as a result of limb loss (Ramachrandan & Hirstein) -> plasticity not always beneficial
- Lack of control over extraneous variables: in studies of recovery (especially from trauma or stroke), variables like rehab, motivation, or education can affect recovery -> hard to establish causal relationships
- Individual differences: age, gender, & life experience can influence plasticity e.g. younger brains are more plastic - however, many studies do not control for these variables -> hard to generalise findings
41
What is a strength of functional recovery? (A03)
- Real-world application: understanding the processes involved in plasticity has contributed to the field of rehabilitation - understanding that axonal growth is possible encourages new therapies to be tried - e.g. constraint-induced movement therapy used with stroke patients whereby they repeatedly practice using the affected part of their body while the unaffected arm is restrained -> useful for medical professionals to know when to intervene
- High control using neuroimaging: studies use objective & scientific tools like fMRI & PET scans - provides real-time & reliable measurements of brain activity, increasing internal validity of findings
42
What are the weaknesses of functional recovery? (A03?
- Cognitive reserve: level of education may influence recovery rates - Schneider et al revealed that the more time brain-injured people spent in education (indication of their cognitive reserve), the greater their chances of disability-free recovery (DFR) -> 40% of those who achieved DFR had more than 16yrs education compared to 10% who had less than 12yrs -> people with brain damage with insufficient DFR = more likely not to fully recover
- Small sample: Banerjee et al treated people who had TACs (type of stroke) with stem cells + found all ppts recovered compared to typical 4% recovery -> study drew conclusions based on just 5 ppts & no control group - typical of functional recovery research -> redcues generalisability
43
What is phantom limb syndrome?
The continued experience of sensations in the missing limb as if it were still there
44
What are the 4 ways of studying the brain?
- fMRI
- EEG
- ERP (Event-related potential)
- Post-mortem examination
45
How do fMRIs work and what do they produce?
- How it works: detects changes in blood oxygenation & the flow that occur due to activity in particular parts of the brain
- Haemodynamic response - when a brain is more active -> needs more oxygen to meet these demands & blood flows to the area in need
- Produces: 3D imaging (activation maps) showing which parts of the brain are active during mental processes, giving understanding of localisation
46
What are the strengths of using fMRIs to study the brain?
- Less invasive & less harmful in comparison to other techniques such as PET scan (doesn't rely on radiation) - more ethical
- High spatial resolution - we get a clear picture of the brain activity
- Highly standardised
- Reduces experimenter bias
- Uses scientific measures
- High internal reliability
- Universal and generalisable
47
What are the weaknesses of using fMRIs to study the brain?
- Very expensive
- Cannot establish cause and effect just a relationship
- Poor temporal resolution, with a 5 second delay from picture to image on screen – lacks validity
- Can cause psychological and emotional stress
48
How do EEGs work, what do they produce, and what are they used for?
- How it works: measures the electrical activity within the brain via electrodes that are fixed to the scalp
- Produces: the scan recording represents the brainwave patterns that are generated from action of neurons
- Used for: diagnosing arrhythmic patterns of activity that may indicate neurological abnormalities such as epilepsy, tumors, sleep disorders
49
What are the strengths of using EEGs to study the brain?
- Usefulness in researching stages of sleep and diagnosis of conditions
- Extremely high temporal resolution (recording in real time)
- Easy to use and inexpensive
- Non-invasive, reduces ethics
50
What are the weaknesses of using EEGs to study the brain?
- Poor spatial resolution, lacks clarity to specific areas
- Uncomfortable to wear, could cause harm
- Hard to establish conclusions as many areas tend to show brain activity, hard to pinpoint specific areas
51
How do ERPs work, what do they produce, and what are they used for?
- ERPs use similar equipment to EEG, electrodes attached to the scalp
- The key difference is that a stimulus is presented to a ppt (e.g. a picture/sound) & the researcher looks for activity related to that stimulus
- ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), - an average response is graphed.
- This procedure, ‘averaging’, reduces any extraneous neural activity which makes the specific response to the stimulus stand out
52
What are the strengths of using ERPs to study the brain?
- Excellent temporal resolution (recording in real time)
- Most scientific in measurements
- Easy to use and inexpensive
- Non-invasive, reduces ethics
- Highly reliable and generalisable
53
What are the weaknesses of using ERPs to study the brain?
- Poor spatial resolution, lacks clarity to specific areas
- Uncomfortable to wear, could cause harm
- Lack of standardisation causing experimenter bias
- Can lack validity due to background data
54
What are post-mortem examinations and what are they used for?
- What happens: involves analysis of a person's brain following their death
- Areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person experienced
- This may also involve comparison to neurotypical brains to obtain the extent of difference.
55
What are the strengths of post-mortem examinations?
- Provide useful information that cannot be obtained by other techniques
- Psychological, physical & emotional harm reduced
- Case study support: Wernicke & Broca and HM and Phineas Gage
56
What are the weaknesses post-mortem examinations?
- Hard to establish cause and effect
- Lacks validity – external factors
- Issues with informed consent
57
What are biological rhythms?
- Biological rhythms: distinct patterns of changes in body activity that conform to cyclical time periods
- Governed by two things:
Endogenous pacemakers: The body's internal biological clocks
Exogenous zeitgebers: changes in the environment
58
What are circadian rhythms?
- Biological rhythms, subject to a 24-hr cycle, which regulate many body processes such as the sleep/wake cycle & changes in core body temperature
59
What research has been conducted into core body temperature? (circadian rhythms)
- Body temp at its lowest at 4am (36 degrees) and peaks at 6pm (38 degrees)
- Folkard et al showed how children who had stories read to them at 3 pm showed superior recall & comprehension after a week compared to children who heard the same stories at 9 am
- Gupta found improved performances on IQ tests when ppts were assessed at 7 pm as opposed to 2 pm and 9 am
60
What is the sleep/wake cycle governed by?
- Governed by internal endogenous pacemaker – a biological clock called the suprachiasmatic nucleus (SCN)
- Located above the optic chiasm which provides information from the eye about light
- Exogenous zeitgebers (light) can reset the SCN
- These biological cycles are synchronised to the daily light-dark cycle of the external environment - affects our sleep & wake times
61
What study did Siffre conduct into sleep/wake cycle?
- Siffre spent two months in the caves of the Southern Alps (1962) deprived of exposure to light & sound - he emerged two months after, but believed it be only 1 month
- A decade later, he performed a similar self-study but for 6 months in a Texan cave
- For both studies, his ‘free-running’ circadian rhythm settled down to around 25 hrs though he continued to fall asleep & wake on a regular schedule
62
What research did Aschoff and Wever conduct into the sleep/wake cycle?
- Similar results were recorded by Aschoff & Wever (1976) who convinced a group of ppts to spend 4 weeks in a WWII bunker deprived of natural light
- Ppts were able to adjust to a 24/25 hour sleep/wake cycle except 1 ppt who developed a sleep/wake cycle of 29 hrs
- Suggests the natural sleep/wake cycle may be slightly longer than 24 hrs but it is entrained by EZs associated with our 24 hr day e.g. light, meal-times etc
63
What are the strengths of research into circadian rhythms? (A03)
- Improved medical treatments: CRs coordinate many of the body’s basic processes e.g. heart rate, digestion - has an effect on pharmacokinetics (the action of drugs on the body + how well they are absorbed & distributed) -> research into CR has revealed that there are certain peak times during day/night when drugs are likely to be at their most effective -> led to development of guidelines to do with the timing of drug dosing for a whole range of medications including anticancer, respiratory drugs (Baraldo)
- Practical application to shift work: knowledge of CR has given researchers a better understanding of the consequences that can occur as a result of their disruption - desynchronisation - Boivin found night shift workers experience a period of reduced concentration around 6am -> mistakes & accidents are more likely - research has also suggested a link between shift work & poor health – Knutson found shift workers are 3 times more likely to develop heart disease (stress of adjusting to different sleep/wake cycles or poor quality sleep during the day -> economic implications for how best to manage worker productivity
64
What are the weaknesses of research into circadian rhythms? (A03)
- Use of case studies/small samples: Studies of the sleep/wake cycle tend to involve small samples (Aschoff & Wever or Siffre - only studied himself) - in most of his recent cave experiment, Siffre at age 60 reported that his internal clock ticked much slower than when he was a young man -> people involved may not be representative of wider population - limits the extent to which generalisations can be made + Siffre himself reported that even when the same person is involved, there are factors that vary which may prevent conclusions to be drawn
- Poor control in studies: Although ppts in the studies discussed were deprived of natural light, still had access to artificial light, e.g. Siffre turned on a light every time he woke up which remained on until he went to bed – was assumed by him & others that artificial light, unlike daylight, would have no effect on the free-running CR - however, Czeisler et al. were able to adjust ppts’ CR from 22 -> 28 hours using dim lighting - light is a confounding variable - low validity
65
What is the difference between ultradian and infradian rhythms?
- Ultradian rhythm: takes less than 24 hours to complete - happens more than once every 24 hours e.g. stages of sleep
- Infradian rhythm: lasts more than 24 hours - happens less than once in 24 hours e.g. menstrual cycle, SAD
66
What research was conducted into individual differences in the sleep-stage cycle?
- Tucker et al
- Monitored people's sleep across a few weeks in his labs - looking at time spent in each of the 5 stages
- No manipulation of any IVs but controlled EVs e.g. light levels (controlled observations)
- Found the biggest variations in people's sleep cycles occurs during deep sleep (stage 3 and 4)
67
What is the difference between endogenous pacemakers and exogenous zeitgebers?
Endogenous pacemakers: structures inside the body that control our biological rhythms e.g. SCN
Exogenous zeitgebers: things in our external environment that influence biological rhythms e.g. light
68
What is the role of melatonin?
- Produced and released by pineal gland
- Pineal gland helps control our circadian sleep/wake cycle, releasing melatonin into the bloodstream -> sleepiness (targets sleep centre)
- Reduces melatonin release in the day -> awake and alert (targets wakefulness centre)
69
What is the suprachiasmatic nucleus (SCN)?
- Located in the hypothalamus
- Sends signals to pineal gland telling it when to increase or decrease melatonin release
- Made up of neurons so communicates with pineal gland via nerve impulses
70
How does light act as an exogenous zeitgeber?
- Acts as a cue to tell our bodies whether its day or night
- Light is picked up by sensory receptors in our eyes (retina) -> communicates with sensory neurons -> relay neurons that travel to the visual cortex or send info on light levels to SCN -> tells SCN whether its day or night -> signals to pineal gland to increases melatonin
71
How do noise and social customs act as exogenous zeitgebers?
- Light outside -> noiser outisde - noise level acts as a cue to pacemakers
- Routines also act as a cue -> we don't need to structure our days this way (social customs) -> gives our body a sense of the time of day
72
What research support is there for exogenous zeitgebers?
- Aschoff and Weber investigated the role of light in sleep/wake cycle by getting ppts to live in a bunker with no access to natural light/clocks - just lamps
- Ppts judged time based on their endogenous pacemakers
- Findings: ppts settled into a longer sleep/wake cycle of 25-27hrs
- Conclusion: EPs overestimate the length of a day + need light (still maintaned a consistent cycle regardless)
73
What animal study provides support for endogenous pacemakers and SCN?
- To test the role of the SCN in controlling circardian rhythms - Ralph removed the SCN of hamsters to see the affect on CR
- 2 groups: 1) Hamsters had normal 24hr sleep/wake cycle, 2) Bred a group to have an abnormal 21hr sleep/wake
- Removed SCNs & transplanted into opposite groups
- Removal of SCN -> lost normal sleep/wake cycle e.g. some slept in short bursts + woke up randomly
- Transplanted hamsters displayed an abnormal 21hr cycle in normal hamsters and 24hr in bred hamsters
74
What research support is there for exogenous zeitgebers in the menstrual cycle?
- Reinberg investigated whether light could act as an EZ
- Case study of 1 female ppt making her live in a cave for 3 months with no natural light - just a lamp
- Her sleep/wake lengthened to 25hrs
- Her menstrual cycle shortened to 25.7 days -> light helps control the menstrual cycle
- Limitation: lacks generalisability + artificial lamp light could reset her menstrual cycle
75
What support does jet lag provide for exogenous zeitgebers?
- When abroad, your exogenous zeitgebers and endogenous pacemakers tell you to do opposite things when moving between time zones -> circadian rhythms become desynchronised
- Lasts a few days as CR resets
- EPs operate in old time zone whilst EZs operate in new one
- Endogenous pacemakers & circadian rhythms become desynchronised from the exogenous zeitgeber in the new time zone
76
How does bright light therapy prevent jet lag?
- People are exposed to bright light a few hours a day, for 3-4hrs before travel
- Artificial bright light can trick SCN into thinking its a different time of day
- Tells SCN its earlier in the day than thought -> shifts circadian rhythm back a few hours -> brings CR closer to local time of travel destination - helps people reset their circadian rhythm to the new time-zone before they travel
77
What is a strength of infradian rhythms? (A03)
- Evolutionary basis: menstrual synchrony is explained by natural selection - may have been advantageous for our distant ancestors to menstruate & become pregnant at the same time - in social groups it allows babies who have lost their mothers during childbirth to be still breastfed -> improves their survival chances -> synchronisation is an adaptive strategy
- Real word application: light therapy is the most effective treatment for SAD - a box which stimulates strong light to reset the body's internal clock -> Sanassi found this helps reduce the effects of SAD in 80% of people + light therapy is preferred & deemed as safer than antidepressants
78
What is a weakness of infradian rhythms? (A03)
- Methodological limitations of synchronisation studies: there are many factors that affect changes in the menstrual cycle e.g. stress, diet - may act as confounding variables -> any supposed pattern in synchronisation could be chance - replications failed (Trevathan et al) -> flawed
79
What is a strength of ultradian rhythm? (A03)
- Improved understanding of age-related changes in sleep: sleep scientists have observed that SWS decreases with age - growth hormone is mostly produced with SWS so is reduced in older people -> Cauter et al said the resulting sleep deficit explains various issues in old age e.g. reduced alertness -> in order to increase SWS, medication or relaxation may be used
80
What is a weakness of ultradian rhythm? (A03)
- Individual differences: Tucker et al found large differences between ppts duration of each sleep stage, particularly stage 3&4 - Tucker suggests these differences are likely biologically determined -> hard to describe 'normal sleep' in a meaningful way
81
What is a strength of endogenous pacemakers? (A03)
- Animal studies are justified (Ralph Hamsters): similar mechanisms that work across species - existence of an SCN & pineal gland in hamsters -> generalisations can be made to human brain as mammalian brain has similar structures
82
What are the weaknesses of endogenous pacemakers? (A03)
- SCN research may obsucure other body clocks: research has revealed there are many CRs in many organs & cells - these peripheral oscillators are found in organs like the lungs, skin etc + influenced by the action of the SCN but also act independently - Damiola et al showed how changing feeding patterns in mice could alter the CR of liver cells by up to 12hrs leaving SCN rhythm unaffected
- Endogenous pace-makers can't be studied in isolation (interactionist): total isolation studies such as Siffre's are rare + Siffre made use of artificial light (lamp) which could have reset his biological clock - in everyday EPs and EZs interact so it makes no sense to separate the two -> lower validity
83
What is a strength of exogenous zeitgebers?(A03)
- Age-related insomnia: evidence suggests that people have poorer quality sleep as they get older - due to natural changes in the CR as we age -> falling asleep earlier & broken sleep at night (Duffy et al)
84
What are the weaknesses of exogenous zeitgebers?(A03)
- Case study evidence: Miles et al recounts the study of a young man, blind from birth who had an abnormal circadian rhythm of 24.9hrs - despite exposure to social cues e.g. regular mealtimes, his sleep/wake cycle couldn't be altered -> social cues alone aren't effective
- EZs don't have the same effects in all environments: people living in the Arctic circle (Inuits in Greenland), have similar sleep patterns all year round, despite spending around 6 months in total darkness -> sleep/wake cycle is mainly controlled by EPs which can override EZs
