biopsychology Flashcards
the nervous system (ao1)
nervous system is a specialised network of checks ub the human body and is our primary internal communication system
it collects, processes and responds to information received from environment
it coordinates the working of different organs and cells in the body
divided into the central nervous system and the peripheral nervous system
CNS- made up of brain and spinal cord
PNS- all the exterior nerves, neurones, receptors and effectors
the PNS is divided into the somatic and autonomic nervous systems
somatic nervous system - facilitates communication between CNS and outside world, made up of sensory receptors that carry information to the spinal cord and brain, and motor pathways that allow the brain to control movement
autonomic nervous system - regulates involuntary actions such as heart rate, digesting food, regulating automatic internal bodily responses, this system is further divided into the sympathetic and parasympathetic
sympathetic nervous system - involved in responses used to help deal with emergencies, responsible for fight and flight, impulses travel from nervous systems to organs
parasympathetic nervous system - relaxes the body after the emergency, responsible for relax and digest
structure and function of neurone (ao1)
typical structure:
neurons contain a cell body with a nucleus containing all the genetic material of the cell
branch like structures hand out from the cell names as dendrites which carry nerve impulses from neighbouring neuron’s to cell body
the axon carries the impulses away from the cell body down the length of the neuron, covered in a fatty layer of myelin sheath which protects the axon and speeds up electrical transmission of the impulse
the myelin sheath is segmented by gaps called nodes of Ranvier, causes the impulse to travel faster as it jumps across gaps in the sheath
at end of axon is axon terminals which communicate with the next neuron in the chain across the synapse
sensory neurons - carry messages from PNS to CNS, have long dendrites and short axons, found in receptors of sensory organs
relay neurons - connect sensory neurones to relay or motor neurons, they have short dendrites and short axons, found in CNS
motor neurons - connect CNS to effectors (muscles and glands), they have short dendrites and long axons, release neurotransmitters that bind ti receptors on muscles
synaptic transmission (ao1)
synaptic transmission refers to the process by which neighbouring neutrons communicate with each other by sending chemical messages across the synapse that separates them
the nerve impulse passes across the synaptic cleft from the presynaptic neuron to the post synaptic neuron
the neurons resting state is negatively charged, when activated by a stimulus it becomes positively charged causing an action potential to occur, creating an electrical impulse tear travels down the axon towards the end of the neuron
once the action potential reaches the axon terminals it must cross the synapse, on the axon terminal are a number of synaptic vesicles containing neurotransmitters
these synaptic vesicles release the neurotransmitter via exocytosis
the neurotransmitter diffuses across the synaptic cleft until it binds with receptors on the membrane of the post synaptic neurone which are activated by the neurotransmitter
the effects of the neurotransmitter are terminated by reuptake where the neurotransmitter is taken back up by the presynaptic neurone where it is stored for later release
excitatory and inhibitory neurotransmitters (ao1)
neurotransmitters are chemical messengers that carry signals from the presynaptic neuron across the synaptic cleft to the receptor site on the post synaptic neuron
can be classed as either excitatory or inhibitory in their action
excitatory neurotransmitters
increase chances to activate or carry out behaviours
examples include adrenaline and dopamine
when binding to post synaptic receptor it causes an electrical charge in the membrane of the post synaptic neuron causing an excitatory post synaptic potential meaning the neuron is more likely to fire
inhibitory neurotransmitters
responsible for calming the mind and body, inducing sleep, filtering unnecessary excitatory signals
examples include serotonin and GABA
when binding to post synaptic receptor causes an inhibitory post synaptic potential making it less likely the neuron will fire
neuron can receive both EPSP and IPSP at once, the likelihood of the cell firing is determined by adding up the excitatory and inhibitory synaptic input (summation)
the strength of an EPSP can be increased via spatial and temporal summation
spatial summation means a large number of EPSP are generated from multiple pre synaptic neurons and are passed onto the same post synaptic neuron at the same time
temporal summation means a large number of EPSPs are generated at the same synapse by a series of high frequency action potentials by a pre synaptic neuron
the rate at which a particular cell fires is determined by synapse activity, if excitatory synapses are more active the cell will fire, if inhibitory synapses are more active the cell will fire slower if at all
the endocrine system (ao1)
the endocrine system works alongside the nervous system, it is a network of glands across the body that secrete chemical messengers called hormones
the system uses blood vessels to transport hormones and different hormones will produce different effects and behaviours
the endocrine system helps the nervous system to control vital functions of the body, it acts more slowly than the nervous system but has very widespread and powerful effects
it regulates cell/organ activity and controls vital processes
releases hormones from glands to bind with receptors
an imbalance of hormones may cause disorders or disease so the endocrine system is important to regulate them
glands in the body will produce hormones which are secreted into the blood stream and affect any cell in the body with the receptor for that particular hormone
most hormones affect cells in several organs or throughout the body leading to many diverse and powerful responses
examples
thyroid gland - thyroxine - regulates body’s metabolism and protein synthesis
adrenal medulla - adrenaline and noradrenaline - flight or fight response, increases hr, blood flow to brain and muscles, releases sores glycogen and fats
adrenal cortex - cortisol, glucose/mineralocorticoids - stress, regulation of water balance, release of stored glycogen and fats
testes - testosterone - development of male secondary sexual characteristics, promotes muscle mass and growth
ovaries - oestrogen - regulation of female reproductive system, menstrual cycle and pregnancy
pineal gland - melatonin - regulation of arousal, biological rhythms and sleep wake cycle
pituitary gland responsible for multiple hormones, TSH, FSH, growth hormone, ADH, oxytocin
flight or fight response (ao1)
when experiencing a stressful or threatening situation, the amygdala is activated, this associates sensory signals with emotions associated with flight or fight such as fear or anger
the amygdala will then send a distress signal to the hypothalamus which communicates wit the rest of the body through the sympathetic nervous system
when the sympathetic nervous system is triggered by the hypothalamus, it begins the process of preparing the body for the rapid action of flight or fight
it sends a signal to the adrenal medulla to secrete the hormone adrenaline into the bloodstream
as the adrenaline circulates it causes physiological changes such as
increased heart rate
increased blood pressure
increased breathing rate
release of glucose stores and fats to supply energy
pupil dilation
sweat production
reduction on non essential functions (digestion, salivation)
the parasympathetic nervous system is in control of dampening the stress response once the threat has passed, it reverses all the physiological changes that adrenaline caused
slows heartbeat
reduces blood pressure
digestion restarts
process known as rest and digest
flight or fight response (ao3)
+ logical from an evolutionary psychology perspective, helped an individual survive by fighting or fleeing a threat, and in these previous times the threat was likely very significant and life threatening therefore having a flight or fight response is appropriate and valid
- some psychologists have criticised the flight or fight response for ignoring an alternative response we engage in being the freeze response, this response is an attempt to avoid confrontation with the threat in which we are hypervigilant while trying to assess the situation to describe best course of action, therefore does not take into account alternative responses to a threat
-the flight or fight response is typically considered a male response to danger while recent research suggests females adopt a tend and befriend response to threats, researchers believe that women are more likely to protect their offspring and form alliances with others rather than fight or flee, as it could be seen as counterintuitive or as a sign of weakness as putting their offspring oat risk, therefore the fight or flight response demonstrates beta bias as it minimises the difference between the response of men and women in a stressful situation - fight or flight will have been a useful survival mechanism for ancestors, however in modern day life we rarely face such life threatening situations, therefore these acute stressors that activate the fight or flight response can have a negative consequence on their health, the changes in blood pressure and heart rate can cause damage to blood vessels and heart, therefore this may be a maladaptive response to everyday life
localisation of function (ao1)
localisation of function refers to the principle that specific functions such as language, memory etc have specific locations in the brain
the brain is divided into 4 regions of the brain
cerebral hemispheres (cerebrum) - split into 2 hemispheres, connected by the corpus collusum, contains 4 lobes
frontal lobe - thought and speech production
occipital lobe - processing of images
temporal lobe - dealing with cognitive skills
parietal lobe - dealing with sensory information
diencephalon - inside cerebrum above the brain stem, responsible for sensory function, food intake and the body’s sleep cycle, divided into the thalamus, hypothalamus, and epithalamus
cerebellum - below and behind cerebrum attached to brain stem, controls motor function, balance, interpreting information from senses
brain stem - connects brain to spinal cord, governs blood pressure, reflexes, flight or fight response, breathing, heart rate
motor cortex - responsible for voluntary movement, located in back of frontal lobe, both hemispheres have a motor cortex
somatosensory cortex - receives sensory input from receptors in skin, located in parietal lobe
visual cortex - responsible for processing visual information from eyes, located in occipital lobe, uses secondary visual areas to convert sensations to perception
auditory cortex - responsible for processing auditory information, mostly lies within temporal lobes in both hemispheres
brocas area - responsible for speech production, language centre, left frontal hemisphere only
wernicke’s area - responsible for language comprehension, written and spoken, posterior portion of left temporal lobe,
localisation of function (ao3)
+ supporting evidence in case studies such as Phineas Gage, suffered a traumatic accident that caused damage to his temporal lobe, this caused a complete change in his personality, therefore suggesting personality may be localised to frontal lobe, this has then been shown within brain scans that the frontal lobe is responsible for regulation of mood
+ many brain scan evidence to prove the localisation of neurological functions particularly in relation to language and memory, study done where brain scans were used to see activity in wernickes area during a listening task and brocas area during a reading task, brain scan showed that language is localised to these areas, increased validity and objectivity of brain localisation
- opposing theory, the theory of plasticity argues against localisation, when the brain is damaged causing the loss of a function, the rest of the brain has the ability to reorganise itself in an attempt to compensate for the lost function, this indicated that other areas have the ability to replicate a function from a different area suggesting functions are not in fact localised to single areas
- brain localisation can be criticised for taking a reductionist approach, study conducted where different rats had different parts of their brain removed whilst learning a maze, however it was found that no single area was most important in affecting the rat’s ability, therefore this function was not localised to a single part of the brain, it could be concluded that higher cognitive processes are distributed holistically allowing the brain to work as a whole
brain lateralisation (ao1)
refers to the idea that the two hemispheres of the brain are not exactly alike, each has functional specialisations and is responsible for certain mental processes and behaviours making the two hemispheres asymmetrical
the left hemisphere is more involved in language processing, whilst the right hemisphere takes responsibility for visual motor tasks and spatial relationships
the brain is contralateral, meaning each hemisphere controls the opposite side of the body, however the two hemispheres are connected allowing the left hemisphere to process information presented to the right hemisphere
the brain has a corpus callous that acts as a communicator between the hemispheres, allowing us to process information holistically
brain lateralisation (ao3)
+ studying lateralisation has allowed us to understand more about multi tasking allowing for practical application to situations, it was found that in domestic chickens, lateralisation is associated with an enhanced ability to perform two tasks simultaneously such as finding food and staying alert for predators, lateralisation has shown to enhance brain efficiency in cognitive demands
+ real life application, believed to have the advantage of increasing neural processing capacity, one hemisphere is always free to engage in another tasks, for example the left hemisphere could work on a language and speech task whilst the right worked on visual and spatial tasks allowing for increased efficiency and ability of the brain
- lateralisation changes with age meaning that the abilities that lateralisation allows us may only be relevant up to a certain age, studies have shown that language becomes more lateralised to the left hemisphere up until 25 but then decreases after that
- lateralisation does not explain brain plasticity as studies have shown how damage to one hemisphere doesn’t not mean they will have an abnormal brain as plasticity allows the other hemisphere to take over and complete tasks for both hemispheres, therefore plasticity allows the brain to overcome potential limitations associated with lateralisation
split brain research (ao1)
used to study brain lateralisation by showing which functions are dominant in each hemisphere
we can study this using epilepsy patients how have undergone surgery to cut the nerve fibres of the corpus collusum to stop their seizures
this surgery stops communication between the left and right hemispheres therefore allowing us to study whether one hemisphere may be more dominant in controlling certain characteristics and behaviours
study conducted by Sperry and Gazzaniga
using these patients he aimed to examine the extent to which the hemispheres are specialised for certain functions
he would present and image/object to the right or left visual field and conducted a series of tasks
the results found that
they can describe the image in the right visual field but not the left
they could pick up the object in left visual field but not say it
they could draw the image in the left visual field but not say it, but right could say it but drawing was worse
the findings demonstrate there are key differences between the hemispheres
the left hemisphere shows to be dominant in speech and language
the right hemisphere shows to be dominant in visual motor tasks
split brain research (ao3)
+ proves the theory of hemispheric lateralisation, as it provides evidence of the dominance in different functions of the hemispheres, the left is responsible for speech and language whilst the right is responsible for visual spatial processing, additionally the right was seen as a holistic processor whilst the left broke down information
+ there was high internal validity, highly controlled experiment using highly specialised and standardised procedures, they used a fixation point to ensure only one eye was tested and there was no influence from the other that may impact the results, therefore the chance of extraneous variables affecting the results was reduced allowing the researcher to establish significant cause and effect in that the hemisphere is dominant in these tasks that is why they are able to complete it, proving hemispheric lateralisation
- methodological issues with the study, split brain patients are rare, therefore had a small sample size of around 11 patients, all differing in age, gender, handedness, age at which they developed epilepsy, age at which they had the surgery
the patients all underwent different operations, in some not all pathways connecting the hemispheres were cut allowing for communication
additionally all patients suffered epilepsy therefore we cannot be sure that the effects of Sperry’s experiment were due to the splitting of the hemispheres rather than the effects of epilepsy or the drugs used to treat epilepsy, therefore the generalisability of the research is threatened so we should be cautious when applying the findings to other theories and patients - split brain research is rarely carried out due to technological advancements in the medical field allowing us to carry out advanced brain scans that do not require brain surgery that tell us about the location and activity of certain areas of the brain, therefore this form of research may no longer be relevant in todays society indicating it lacks temporal validity
neuroplasticity and functional recovery (ao1)
plasticity refers to the ability of the brain to change and adapt synapses, pathways, and structures in light of various experiences
these experiences can be positive such as learning or memory, but it can also be to adapt to damage caused by trauma
in childhood, the brain is highly plastic allowing the baby to develop as they are exposed to a vast range of experiences/environments/stimuli, the brain needs to have the ability to learn and form new neurons and connections, learn new skills, adapt to environment, and recover from brain injury
as people gain new experiences the nerve pathways that are used frequently develop stronger connections, however with age there is a natural decline in cognitive function due to changes with the brain, and alongside this with age plasticity of the brain decreases
functional recovery after trauma simply means the transfer of functions from a damaged area of the brain to other undamaged areas
the brain is able to rewire and reorganise itself by forming new synaptic connections close to the damage
the process of recovery is supported by structural changes such as
axonal sprouting - growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways
denervation supersensitivity - axons that do a similar role to the damaged axon became aroused to a higher level to compensate for the lost ones
recruitment of homologous areas - if one part of the brain is damaged on one hemisphere the same area on the opposite hemisphere can take up the role and carry out the function, over time functionality may return to original side
neuronal unmasking - dormant synapses are unmasked by damage which increases input to the synapse allowing new connections to open to other regions of the brain that are not normally activated
neuroplasticity and functional recovery (ao3)
+ research support, Maguire studied London taxi drivers to determine whether changes in the brain could be detected due to their experience in spatial navigation, using mri scanners they found that the front portion of the hippocampus was larger than controls and that it was positively correlated with the length of time they had spent driving taxis. this is key evidence of brain plasticity and the brain ability to develop nerve pathways and deepen strong neural connections causing the area to grow
- negative plasticity, one limitation of plasticity is that it may have negative behavioural consequences, evidence has shown that the brains adaption to prolonged drug use leads to a poorer cognitive functioning in later life alongside an increased risk of dementia, therefore the brains ability of plasticity may not always be beneficial and can have negative consequences to our health
+ by understanding the processes involved in function recovery we can apply this to practical situations, this has contributed to the neuro rehabilitation field, in which doctors can provide therapy and electrical stimulation of the brain to counter the deficits in motor or cognitive functioning, it is used once natural recovery tends to slow down showing that functional recovery is efficient up to a certain point and even after that our knowledge of it can help develop therapies to further recovery with intervention
-there have been gender differences found in research that suggests that women can recover better from brain injury as their functions have shown to not be as lateralised as men, in a study using patients who have suffered brain trauma and had been rehabilitated who were then tested for their level of cognitive skills, it was found that women performed more significantly than men on tests of attention/working memory/language whilst men outperformed women in analytical skills, overall it was shown that women had a better recovery and higher level of cognitive skill, indicating that the theory of function recovery may have beta bias and is minimising the differences between the ability for the brain to recover in men and women
ways of studying the brain (ao1)
scanning techniques started with ct scans (computed axial tomography) which used x rays to take images of brain structures highlighting major structures and abnormalities
replaced by MRI (magnetic resonance imaging) that used string magnetic fields and radio waves to produce highly detailed images of the brain
PET (positron emission tomography) was then introduced where a radiative substance was injected to blood stream and travelled to brain where the most active regions would accumulate the most of it allowing it to be emitted and picked up by scanner
fMRI - functional magnetic resonance imaging
developed from the mri scanner, basis is that neurones that are active during a task will use more energy therefore requiring more oxygen and blood, the fmri scan indirectly measures blood flow through the concentration of oxygen in the blood stream, signal used is Blood Oxygen Level Dependent contrast, allows us to understand more about brain localisation but can also be used in lie detection
EEG - electroencephalogram
provides an overall view of brain electrical activity, several small recording electrodes are distributed over the surface of the skull, picking up the electrical activity of the millions of neurones, can characterise the amplitude (size/intensity of electrical activity) and the frequency (speed/rapidity of electrical activity), has two distinctive states synchronised pattern forming a recognisable waveform and desynchronised pattern where there is no recognisable waveform, used to detect brain disorders or to diagnose other disorders that influence brain disease
ERP - event related potentials
very small voltage changes in the brain triggered by stimuli are measured using similar recording electrodes to eegs, but key difference is that the psychologist looks for specific electrical responses to a stimulus like a sound or picture and this is repeated until the electrical response becomes clear
Post Mortem Examination
aka autopsies, researchers study the physical brain of a deceased person who was studied for potential brain damage during their life, their brain can then be compared to others to look for abnormalities that explain the abnormal behaviours they displayed, allows for study of both anatomical aspects and neurochemical aspects of the brain helping to contribute to the understanding of many disorders, recently technology has furthered to allow for brain scans on deceased individuals to avoid having to dissect the brain.
ways of studying the brain (ao3)
fMRI
+ fMRI do not rely on the use of radiation unlike other scanning techniques, they are non invasive, participant only required to remain still and quiet, virtually a risk free technique, this allows patients to be more encouraged to undertake these scans helping psychologists to gather further data on the functioning brain and therefore develop our understanding of localisation
- do not provide a direct measure of neural activity, they simply measure changes in blood flow and therefore we cannot accurately infer causation, changes in blood flow may indicate activity within a certain area we cannot conclude whether this brain region is associated with the particular function
EEG
+ provide a recording of the brains activity in real time rather than a still image, a researcher can accurately measure a particular task or activity and the electrical activity occurring at this time, therefore eegs have good temporal resolution (ability to measure changes over time)
- can only detect the activity in the surperficial regions of the brain, cannot reveal the activity of the deeper regions like hippocampus or hypothalamus, therefore it is not a practical way of studying all areas of the brain as we can only investigate some
ERP
+ can measure the processing of stimuli even in the absence of a behavioural response, erp recordings make it possible to monitor the signals covertly when the participant is processing a particular stimulus without requiring the person to respond, this means that we can collect valid data as there is reduced chance the results have been affected by social desirability bias or demand characteristics
- poor spatial resolution, electrodes are spread all over the scalp allowing us to localise areas of the erp to general areas of the cortex, but we cannot localise to specific areas as we cannot be sure which areas are active and responsible for specific behaviours and responses
post mortem examinations
+allow for a much more detailed investigation into the brain including anatomical and neurochemical aspects that a superficial scan would not be able to pick up, it has enabled researchers to understand the deeper regions of the brain like the hypothalamus and hippocampus that cannot be done with the other alternatives providing invaluable research and evidence to diagnosis of disorders and psychological theories
- criticised for individual differences, the deceased individuals who are investigated likely died in different ways and at different stages of the disease and life itself, the length of time between death and examination, drug treatments they may have followed and age at death will all become confounding variables that will affect the outcome of the examination, therefore due to these differences we cannot make generalisations to the general public about brain functioning from the results
circadian rhythms (ao1)
biological rhythms - distinct patterns of change in body activity that follow cyclical time periods
circadian rhythms - biological rhythms that last around 24 hours, therefore will occur once every 24 hours
one example is the sleep wake cycle, governed by exogenous zeitgebers of light and endogenous pacemaker of SCN (suprachiasmatic nuclei) in the hypothalamus
scn receives information about light levels from the optic chiasm which resets the cycle to keep us in synchrony with the outside world
light and dark are the external signals that determine when we feel the need to sleep and wake up, the rhythm dips and rises at different times of the day so that our strongest sleep drive is between 2am-4am and 1pm-3pm, the sleepiness will be inversely proportionate to the sleep we got the night before, sufficient sleep=less sleepy, sleep deprived=more sleepy
the release of melatonin from the pineal gland, is at its peak during the hours of darkness, melatonin induces sleep by inhibiting the neural mechanisms that promote wakefulness, light suppresses the production of melatonin
sleep and wakefulness are also under homeostatic control, when we have been awake for a long time homeostasis tells us that our need for sleep is increasing because of the energy used when awake, the homeostatic drive for sleep increases gradually until reaching maximum in the late evening
circadian rhythms keep us awake during daylight hours and prompts us to sleep as it becomes dark, the homeostatic system tends to make us sleepier the longer we have been awake regardless of light/dark, this is because our internal circadian rhythm will maintain a cycle of 24/25 hours even without exogenous zeitgebers
circadian rhythms (ao3)
+ research support, a cave explorer who was investigating the human internal clock spent several extended periods in a cave with no natural light and any means of telling time, there were no external cues to guide the rhythms so it was solely dependent on his endogenous pacemakers keeping his internal circadian rhythm synchronised, on these occasions his free running biological rhythm settled at around 25 hours proving support in stating that the sleep wake cycle is a circadian rhythm and has the ability to stay synchronised purely using endogenous pacemakers and our internal body clock
+ there are practical applications that come from the research into circadian rhythms, in that it has helped with the efficiency of drug treatments in deciding times for taking medication. with drug treatments, the timing of release and concentration are very important to ensure the drug works as it should, once example is heart attack medicine where the risk of heart attacks are greatest in the morning therefore for most efficiency medicines should be released in the early morning, this has allowed for the development of drugs that can be taken before sleep and that are released in the morning , this research has allowed us to understand the body more and adapt our medicines to help more people
- research into circadian rhythms uses case studies that are made up of small sample sizes therefore we can question generalisability of the findings as well as whether the results can be considered truly representative of the target population, there are many factors that may mean the individual differs from the target population such as age, gender, health which with such a small sample size cannot represent the entire target population
- there was an important flaw to early research into the sleep wake cycle which likely impacted the results, where individuals were isolated from anything that could affect their circadian rhythm, they were not isolated from sources of artificial light such as a torch that could still act as an exogenous zeitgeber which could have altered their circadian rhythm itself, in fact research has shown that people’s circadian rhythm was able to be altered to make it both shorter and longer by manipulating the use of artificial light, suggesting the findings of the studies are invalid and circadian rhythms may not be as free-running and accurate.
ultradian rhythms (ao1)
biological rhythms - distinct patterns of change in body activity that follow cyclical time periods
ultradian rhythms - biological rhythms that last less than 24 hours, therefore will occur multiple times in 24 hours
one example is the patterns of human sleep and the stages of sleep we go through
the sleep cycle alternates between REM sleep (rapid eye movement) and NREM (non rapid eye movement) and consists of five stages
the cycle repeats around every 90 minutes through the night
the stages have been investigated using EEG where they found distinctive brain wave patterns in each stage
(nrem) stage 1/2 - are light sleep stages where brain patterns are slower and more rhythmic starting with alpha waves and going to theta waves
(nrem) stages 3/4 - are deep sleep and are slower wave sleep stages, it is difficult to wake someone from this stage and is associated with slow delta waves
(rem) stage 5 - REM dream sleep where the body in paralysed to prevent acting out dreams and brain activity resembles that of a conscious person with EEG detecting theta waves
BRAC - basic rest activity cycle
the 90 minute cycle that occurs during sleep continues during the day
individuals will move from a 90 min state of alertness to physiological fatigue
from the we have been able to conclude that the human mind can only focus for a period of 90 minutes then the body begins to run out of energy
ultradian rhythms (ao3)
+ research support for the stages of sleep, study took EEG measurements throughout participants sleep and were woken up throughout the sleep to determine their sleep cycle stage, findings showed all participants had periods of REM sleep, when participants were awoken during REM sleep they could recall their dream but not in other stages, therefore we can conclude that stages of sleep follow a typical pattern through the night
- individual differences in sleep patterns so we cannot generalise the stages of sleep to the whole population, there may be idndividual differences which are biologically determined or even genetic that affect the stages of sleep, therefore we should be cautious with generalising research on the stages of sleep as some people who do not follow these stages do not necessarily have abnormal sleep
infradian rhythms (ao1)
biological rhythms - distinct patterns of change in body activity that follow cyclical time periods
infradian rhythms - biological rhythms that last longer than 24 hours, therefore will occur once in a time period longer than 24 hours
one example is the female menstrual cycle, this is regulated by hormones that will either promote ovulation or stimulate the uterus for fertilisation, the oestrogen levels will rise causing ovulation which occurs roughly halfway through the cycle and usually lasts 16-32 hours
after ovulatory phase progesterone levels will rise which thickens the lining of the womb in preparation for pregnancy, usual cycle around 28 days but can very from person to person
known to be an endogenous system but some evidence has begun to suggest it can be influences by exogenous factors such as cycles of other women around
another example is SAD (seasonal affective disorder)
research has shown there can be seasonal variation in mood where some people become depressed in the winter and mood rises in the summer month making this a yearly infradian cycle
psychologists have claimed that the release of melatonin from the pineal gland is partly responsible as the lack of light during the winter months result in longer periods of melatonin secretion linking to depressive symptoms
infradian rhythms (ao3)
+ the research into the exogenous factors other other women’s cycles can have useful practical applications, evolutionary psychologists have claimed that the synchrony of menstrual cycles provides an evolutionary advantage for groups if women as it can allow for childcare to be shared amongst groups of women who have had children at the same time. therefore this research can be helpful in providing practical advantages to everyday life and help women build a sense of community together in raising their children
- there are methodological limitations to the studies investigating menstrual synchronisation, there are many other factors that may affect the menstrual cycle separate from hormones and other women, for example stress, diet, exercise, these can therefore be considered confounding variables which may explain why other studies cannot replicate the findings of another, this suggests that these studies are flawed and the findings are invalid questioning whether this is appropriate evidence to support the menstrual cycle as an infradian rhythm
+ research support to evidence sad and the role of melatonin within it, studies have shown that the rate of SAD is more common in northern countries where winter nights are longer and is less common in southern countries where they are shorter, this indicates that SAD may be affected by the exogenous zeitgeber of light and its resulting changes in melatonin secretion
endogenous pacemakers and exogenous zeitgebers (ao1)
