Psychology- Biopsychology

what is the nervous system?

-specialised network of cells in the human body and primary internal communication system

-based on electrical and chemical signals

-2 main functions: to collect, process and respond to information in the environment and to coordinate the working of different organs and cells

explain the nervous system

The Central Nervous System (CNS)

-made up of the brain and spinal cord

-brain is the centre of all conscious awareness, the outer layer, the cerebral cortex is only 3mm thick and covers the brain - only in mammals

-distinguishes our higher mental functions from others

-divided into two hemispheres

-spinal cord is an extension of the brain, passes messages to and from the brain and connects nerves to the PNS. responsible for reflex actions

The Peripheral nervous system (PNS)

-transmits messages via million of neurons to and from the central nervous system, subdivided into the

-autonomic nervous system (ANS) governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses

-somatic nervous systems (SNS) governs muscle movement and receives information from sensory receptors

what is the endocrine system and how is it different to the nervous system?

-endocrine system works alongside the nervous system to control vital functions in the body

-endocrine system acts more slowly than the nervous system but has very widespread and powerful effects

how do glands and hormones work in the endocrine system?

-various glands such as the thyroid gland produce hormones

-hormones are secreted into the blood stream and affect any cell in the body that has receptor for that particular hormone

-most hormones affect cells in more than one body organ, leading to diverse and powerful responses ( e.g thyroid produces thyroxine, affects cells in the heart and increases metabolic rates, thus growth rates)

-key gland is the pituitary gland in the brain- controls the release of hormones from all the other endocrine glands in the body

explain how the endocrine system and ANS work together to create fight or flight

-when a stressor is perceived , first the hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch of the autonomic nervous system

-ANS changes from its normal resting state (parasympathetic) to the physiologically aroused sympathetic state

Adrenaline: released from the adrenal medulla into the blood stream, triggers physiological changes in the body which creates the physiological arousal necessary for the fight or flight response

Immediate and automatic: happens in an instant as soon as threat is detected. An acute response and automatic reaction in the body

Parasympathetic action: the parasympathetic nervous system returns the body to its resting state, the branch of the ANS works in opposition to the sympathetic nervous system- actions are antagonistic to the sympathetic system, it acts as a 'brake; and reduces activities of the body that were increased by actions of sympathetic- rest and digest response

explain localisation vs holistic theory

-scientists used to believe that all parts of the brain were involved in processing thought and action

-scientists such as Broca and Wernicke discovered that specific areas of the brain were associated with particular physical and psychological functions

-this is localisation of function which is that different parts of the brain perform different tasks

what are the hemispheres of the brain

-main part of brain (cerebrum)is divided into left and right

-activity on left hand side of body controlled by right and activity on right controlled by left

-language is linked to the left

explain the centres of the brain

-the cerebral cortex is the outer layer of both hemispheres, cortex is subdivided into 4 centres called 'lobes'

-the 4 lobes are: frontal, parietal, occipital and temporal

-at the back of the frontal lobe (in both hemispheres) is the motor area which controls voluntary movement in opposite side of the body, damae many result in loss of control of fine movements

-at the front of both parietal lobes is the somatosensory area separated from motor area by 'valley' called central sulcus

-this is where sensory info from the skin is represented, the amount of somatosensory area devoted to a particular body part denotes its sensitivity

-in the occipital lobe at the back of the brain is the visual area each eye sends info from right visual field to left visual cortex and left VF to right VC sk damage to left hem can produce blindness in rght vs

-the temporal lobes house the auditory area which analyses speech based info, damage may produce partial hearing loss

describe and explain the language centres of the brain

evaluate localisation of function

STRENGTH: damage to areas of the brain has been linked to mental disorders

-neurosurgery is a last resort for treating MD targeting specific areas of the brain

-e.g. cingulotomy involves isolating a region called cingulate gyrus which has been implicated in OCD, Dougherty et al reported on 44 people with OCD who had undergone a cingulotomy , after 32 weeks 30% were successful response and 14% partial

-the success shows that behaviors associated with serious MD may be localised

STRENGTH: evidence from brain scans supports the idea that many everyday brain functions are localised

-Petersen et al used brain scans to demonstrate how Wernicke's area was active during a listening task and Broca's area was active during a reading task

-a review of LTM by Buckner and Petersen revealed that semantic and episodic memories reside in diff parts of prefrontal cortex

-thus objective methods for measuring brain activity have provided scientific evidence

COUNTERPOINT: Lashley removed areas of cortex (10%-50%) in rats that were learning route of maze

-no area was proven to be more important than any other area in ability to learn route

-process of learning seemed to require every part of the cortex rather than confined

LIMITATION: language may not be localised just to Broca's and Wernicke's areas

- a review by Dick and Tremblay found only 2% of modern researchers think that language in the brain is controlled by Broca and Wernicke

-advances such as fMRI mean that neural processes can be studies - language function seems to be far more holistically distributed, language streams have been identified across cortex including subcortical regions and the thalamus

-Phineas Gage

describe the structure of a neuron

-cell body includes a nucleus which contains the genetic material of the cell

-branchlike structures called dendrites protrude from the cell body carrying nerve impulses from neighbouring neurons towards the cell body

-the axon carries impulses away from the cell body down the length of the neuron

-axon is covered in fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse

-if myelin sheath was continous this would have the reverse effect and slow down electrical impulse, the myelin sheath is segmented by gaps called nodes of Ranvier

-these speed up transmission of impulse by forcing it to 'jump' across gaps along the axon

-at the end of the axon are terminal buttons that communicate with the next neuron in the chain across the synapse

describe the types of neurons and their functions

Sensory neurons-carry messages from the PNS to the CNS

-long dendrites and short axons

Relay neurons-connect the sensory neurons to the motor or other relay neurons

-short dendrites and sort axons

Motor neurons- these connect the CNS to effectors such as muscles and glands

-short dendrites and long axons

where are neurons located and what is electrical transmission

location- cell bodies of motor neurons may be in the CNS but they have long axons which form part of the PNS

-sensory neurons are located outside of the CNS in the PNS in clusters known as ganglia

-relay neurons make up 97% of all neurons and most are found within the brain and visual system

electrical transmission- when a neuron is in a resting state the inside of the cell is negatively charged compared to the outside

-when a neuron is activated by a stimulus the inside becomes positively charged for a split second causing action potential to occur, creates an electrical impulse that travels down the axon towards the end of the neuron

what are the 4 components of synaptic transmission

-chemical transmission, neurotransmitters, excitation and inhibition, summation

explain chemical transmission

-neurons communicate within neural networks

-each neuron separated from the next by a synapse

-signals within neuron's are transmitted electrically however signals between neurons are transmitted chemically across synapse

-when electrical impulse reaches the end of the neuron ( presynaptic terminal) it triggers the release of a neurotransmitter from tiny sacs called synaptic vesicles

explain/describe neurotransmitters

-neurotransmitters are chemicals that diffuse across the synapse to the next neuron in the chain

-once a neurotransmitter crosses the gap, it is taken up by a postsynaptic receptor site on the dendrites of the next neuron, chemical message is converted back into an electrical impulse and process of transmission begins again in this other neuron

-direction of travel can only be one way, neurotransmitters are released from the presynaptic neuron terminal and received by postsynaptic neuron

-several dozen types of neurotransmitters have been identified in the brain, each neurotransmitter has its own specific molecular structure that fits perfectly into a postsynaptic receptor site, similar to lock and key

-neurotransmitters have specialist functions, for instance acetylcholine is found at each point where a motor neuron meets a muscle and upon its release it will cause muscles to contract

explain excitation and inhibition

-neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron

-e.g. the neurotransmitter serotonin causes inhibition in the receiving resulting in the neuron becoming more negatively charged and less likely to fire

-in contrast, adrenaline causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire

descrive summation

-wether a postsynaptic neuron fires is decided by the process of summation

-excitatory and inhibitory influences are summed- if the net effect on the postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire

-if the net effect is excitatory it is more likely to fire, the inside of the postysnaptic neuron momentarily becomes positively charged

-once the electrical impulse is created it travels down the neuron

-the action potential of the postsynaptic neuron is only triggered if the symptoms of the excitatory and inhibitory signals at any one time reaches the threshold

explain localisation and lateralisation

-localisation- refers to the fact that some functions, such as vision and language, governed by specific areas

-brain is lateralised (two hemispheres) , some functions, localised areas appear in both hemispheres

describe the left and right hemispheres and how they work

-for language, two main centres are only in LH - Brocas area in left frontal lobe and Wernicke's area is left temporal love

-language therefore is lateralised, RH can only produce rudimentary words and phrases

-therefore LH is analyser and RH is the synthesiser

-vision, motor, somatosensory areas are in both hemispheres

-in motor areas the brain is cross wired, RH controls left movement and LH controls right movement

-vision is contralateral and ipsilateral - each eye receives light from LVF and RVF

-LVF of both eyes is connected to the RH and the RVF of both eyes is connected to the LH

-enables the visual areas to compare the slightly different perspectives from each eye and aids depth perception

-similar arrangement for auditory input to the auditory are and disparity from two inputs helps us locate source of sounds

explain what split brain research is

-split brain operation involves severing the connection between the RH and LH mainly the corpus callosum

-surgical procedure used to reduce epilepsy

-during epileptic seizure the brain experiences excessive electrical activity which travels from one hem from the other

-to reduce fits connections are cut, 'splitting' the brain in two halves

describe Sperry's research- procedure and findings

Procedure

-11 people had split brain operation where an image could be projected to a participant's RVF and the same or diff image could be projected to the LVF

-because it is split, info cannot be conveyed from that hemisphere to the other

Findings

-when picture of object was shown to RVF (Linked to LH), the participant could describe what was seen, could not do this If picture was shown to LVF (RH), they said they saw nothing

-in connected brain, messages from RH relay to lang centres in LH, not possible in split brain

-participants could not give verbal labels to objects projected to LVF, could select a matching object out of sight using their left hand (RH) and select an object that was most closely associated with an object presented to LVF

-if a pinup picture was shown to LVF, emotional reaction but participants usually reported seeing nothing or just flash of light

Conclusions

-certain functions are lateralised in the brain and support view that LH is verbal and RH is emotional

evaluate hemispheric lateralisation

STRENGTH: research showing that even in connected brains the two hemispheres process information differently

-Fink et al used PET scans to identify which brain areas were active during a visual processing task

-when participants with connected brains were asked to attend to global elements of an image (eg whole forest) regions of RH much more active

-when required to focus on finer details the specific areas of LH dominated

-hemispheric lateralisation is a feature of connected brain swell as split brain

LIMITATION: the idea that the LH as analyser and RH as synthesiser may be wrong

-may be different functions in the RH and LH, but research suggests people do not have a dominant side of their brain which created a different personality

-Nielsen et al analysed brain scans from over 1000 people aged 7-29yrs and did find that people used certain hemispheres for certain tasks

-no evidence of a dominant side

STRENGTH:

-lateralisation is adaptive as it enables 2 tasks to be performed simultaneously with greater efficiency

-Rogers et al showed lateralised chickens could find food while watching for predators but 'normal' chickens couldn't

-on the other hand, neural plasticity could also be seen as adaptive

-following damage through illness or trauma, some functions can be taken over by non specialised areas in opposite hemispheres

-eg language function can literally 'switch sides'

evaluate split brain research

STRENGTH: support from more split brain research

-Gazzaniga showed split brain patients perform better than connected controls on certain tasks

-eg they were faster at identifying the odd one out of an array of similar objects than normal controls

-in normal brain, the LH's better cognitive strategies are 'watered down' by inferior RH

-supports Sperry that left and right brain distinct

LIMITATION: casual relationships are hard to establish

-behaviour of sperry's participants was compared to a neurotypical control group

-none of participants in the control group had epilepsy

-major confounding variance

-any differences between two groups may be result of epilepsy rather than split brain

-some unique features may have been due to epilepsy

STRENGTH:

-split brain operation not performed for purpose of research

-sperrys participants were not deliberately harmed, all procedures were explained to split brain participants and their full informed consent was obtained

However-

-trauma of operation might have meant participants did not fully understand the implications of what they had agreed to do

What is brain plasticity?

-the brain would appear 'plastic' as it has the ability to change throughout life

-during infancy, brain experiences rapid growth in the number of synaptic connections it has, peaking at 15,000 per neuron at 2-3yrs old

-this is twice as many as there are in an adult brain

-as we age, rarely-used connections are deleted and frequenrly-used connections are strengthened- a process known as synaptic pruning

-this allows lifelong plasticity where new neural connections are formed in response to new demands on brain

describe research into plasticity

-Maguire et al studied brains of london taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than in matched control group

-part of brain is associated with development of spatial and navigational skills

-as part of training, must take a complex test called 'The Knowledge' which assesses their recall of city streets and possible routes

-Maguire et al found that this learning experience alters the structure of their brains- longer been in job, more pronounced was structural difference (pos coll)

-Draganski et al imaged the brains of medical students 3 months before and fater final exams.

-learning induced changes were seen to have occured in posterior hippocampus and the parietal cortex as a result of learning

what is functional recovery in the context of after brain trauma

-unaffected areas of the brain are able to adapt and compensate for those areas that are damaged

-the functional recovery that may occur in the brain after trauma is an example of neural plasticity

-healthy brain areas may take over the functions of those areas that are damaged, destroyed, missing

-neuroscientists suggest that this process can occur quickly after trauma (spontaneous recovery) and then slow down after several weeks or months

-atp the individual may require rehabilitative therapy to further their recovery

explain what happens in the brain during recovery

-the brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage

-secondary neural pathways that would not typically be used to carry out certain functions are activated or 'unmasked' to enable functioning to continue, often in same way as before

-this process:

-axonal sprouting- the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways

-denervation supersensitivity- this occurs when axons that do a similar job become aroused to a higher level to compensate for the ones that are lost. hwv, can be the negative consequence of oversensitivity to messages such as pain

-recruitment of homologous (similar) areas on the opposite side of the brain- specific tasks can still be performed

-e.g. Brocas area damaged on left side of brain, right side equivalent would carry out its functions, after period of time, functionality may sift back to left side

evaluate plasticity

STRENGTH: brain plasticity may be a life long ability

-in general plasticity reduces with age, however Bezzola et al demonstrated how 40 hours of golf training produced changes in the neural representations of movements in participants aged 40-60

-using fMRI, researchers observed increased motor cortex actively in the novice golfers compared to control group, suggesting more efficient neural representations after training

-this shows neural plasticity can continue throughout the lifespan

LIMITATION: it may have negative behavioural consequences

-evidence has shown that the brain's adaptation to prolonged drug use leads to poorer cognitive functioning in later life and an increased risk of dimentia

-60-80% of amputees have been known to develop phantom limb syndrome- continued experience of sensations in the missing limb as if it was still there - unpleasant and painful and thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss

-suggests brain ability to adapt to damage is not always beneficial

evaluate functional recovery

STRENGTH: research has real world application

-understanding plasticity has contributed to the field of neurorehabilitation. simply understanding that axonal growth is possible encourages new therapies to be tried

-e.g. constraint induced movement therapy is used with stoke patients whereby the repeatedly practise using the affected part of their body while the unaffected arm is restrained

-this shows research into functional recovery is useful as it helps medical professionals know when interventions need to be made

LIMITATION: level of education may influence recovery rates

-Schneider et al revealed that the more time people with a brain injury had spent in education- taken as an indication of their 'cognitive reserve' , the greater their chances of a disability-free recovery (DFR)

-40% of those who achieved DFR had more than 16yrs in education compared to 10% of those who had less than 12yrs education

-this would imply that people with brain damage who have insufficient DFR are less likely to achieve full recovery

name the 4 ways of studying the brain

functional magnetic resonance imaging, electroncephalogram, event related potentials, post mortem examinations

explain functional magnetic resonance imaging

(fMRI) works by detecting the changes in both blood oxygenation and flow that occur as a result of neural brain activity in the specific parts of the brain

-brain area is more active it consumes more oxygen and to meet this increased demand blood flow is directed to the active area (haemodynamic response)

-fMRI produces three dimensional images showing which parts of the brain are involved in particular mental processes, shown important implications for localisation of function

explain what is electroencephalogram

(EEG) measures electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap

-scan recording represents the brainwave patterns that are generated from the actions of thousands of neurons providing overall account of brain activity

-EEG is often used by clinicians as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, tumours

what are event related potentials

-EEG has many scientific and clinical applications in its raw form its crude amd overly general measure of brain activity

-within EEG data are contained all the neural responses associated with specific sensory cognitive and motor events that may be of interest to cog neuroscientists

-using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out leaving only those responses that relate to the presentation of a specific stimulus or performance of a specific task

-what remains are event-related potentials (ERPs) which are types brainwave that are triggered by particular events, research has revealed many different forms of ERP and how these are linked to cog processes such as attention and perception

explain post mortem examinations

-technique involving the analysis of a persons brain following their death

-individuals whose brains are subject to a post moterm examination are likely to be those who have a rare disorder and experienced unusual deficits in cognitive processes or behaviour during their lifetime

-areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person experienced

-may invlove comparison with neurotypical brain to ascertain the extent of the difference

evaluate functional magnetic resonance imaging

STRENGTH: unlike other techniques such as PET it does not rely on the use of radiation

-if administered correctly it is virtually risk free, non invasive and straightforward to use

-produces images that have high spatial resolution, depicting detail by the millimetre and providing a clear picture of how brain activity is localised

LIMITATION: expensive compared to other neuroimaging techniques

-poor temporal resolution because there is around a 5 second time lag behind the image on screen and the initial firing of neuronal activity, may not truly represent moment to moment brain activity

evaluate electroencephalogram

STRENGTHS: been useful in studying the stages of sleep and in diagnosis of conditions such as epilepsy

-unlike fMRI, EEG technology has extremely high temporal resolution it can accurately detect brain activity at a resolution of a millisecond, shows the real world usefulness of the technique

LIMITATION: the generalised nature of the information received

-EEG signal is also not useful for pinpointing the exact source of neural activity

-therefore it does not allow researchers to distinguish between activities originating in different but adjacent locations

evaluate event related potentials

STRENGTHS: limitations of EEG partly addressed through the use of ERPS

-bring much more specificity to the measurement of neural processes than could ever be achieved using raw EEG data

-as ERPs are derived from EEG measurements they have excellent temporal resolution, when compared to neuroimaging techniques such as fMRI this means that ERPs are frequently used to measure cognitive functions and deficits such as the allocation of attentional resources and the maintenance of working memory

LIMITATIONS:v a lack of standardisation in ERP methodology between different research studies which makes it difficult to confirm findings

-further issue is that to establish pure data in ERP studies, background 'noise' and extraneous material must be completely eliminated may not always be easily achieved

evaluate post mortem examinations

STRENGTHS: vital in providing a foundation for early understanding of key processes in the brain

-Broca and Wernicke both relied on post mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility

-post mortem studies were also used to study HM's brain to identify areas of damage which could then be associated with his memory deficits

LIMITATIONS: causation is an issue within these studies

-observed damage toi the brain may not be linked tot the deficits under review but to some other unrelated trauma or decay

-post moterm stydies raise ethical issues of consent from the individual before death

-participants may not be able to provide informed consent for example in the case of HM who lost his abiliy to form memories and was not able to porvide such consent

what are biological rhythms

-exert an important influence on the way in which body systems behave

-all bio rhythms are governed by the body's endogenous pacemakers (internal clocks) and external cues which are exogenous zeitgebers

-some rhythms occur during the day (ultradian rhythms) some take longer than a day (infradian rhythms) in some cases much longer

-circadian rhythms last around 24 hours and two examples are sleep/wake cycle and core body temperature

explain the sleep/wake cycle

-the effect of daylight (exogenous zeitgeber) on sleep/wake cycle is why we r drowsy at night and alert in day

-governed by internal pacemaker, a body clock called the suprachiasmatic nucleus (SCN)

-the SCN lies just above the optic chiasm which provides information from the eye about light, exogenous zeitgebers can reset the SCN

describe siffre's cave study

-spent several extended period underground to study the effects on his own biological rhythms, deprived of exposure to natural light and sound

-spent 2 months in southern alps, thought he had only spent a month

-spent 6 months in texan cave

-his 'free-running' biological rhythm settled down to one that was just beyond the usual 24 hours, though he did have regular falling asleep cycle

describe other research done on circadian rhythms

-Aschoff and Wever who convinced a group of participants to spend 4 week in a WW2 bunker deprived of all natural light

-all but one of participants displayed circadian rhythm between 24-25 hours

-both this and Siffre suggest that the 'natural' sleep/wake cycle may be slightly longer than 24 hours but it is entrained by exogenous zeitgebers associated with our 24 hour day

-Folkard et al studied a group of 12 people who agreed to live in a dark cave for 3 weeks, retiring to bed when the clock said 11:45 pm and rising when it said 7:45 am

-over course of study, researchers gradually sped up the clock so an apparent 24 hour day only lasted 22, only one participant was able to comfortably adjust to the new regime, suggest existence of strong free running circadian rhythm that cannot easily be overridden by exogenous zeitgebers

evaluate circadian rhythms

STRENGTH: it provides an understanding of the adverse consequences that occur when they are disrupted (desynchronisation)

-night workers engaged in a shift work experience a period of reduced concentration around 6am meaning

-research has pointed to a relationship between shift work and poor health- shift workers are 3x more likely to develop heart disease than people who work more typical work patterns

-this shows research into sleep/wake cycle may have real world economic implications

COUNTERPOINT: studies investigating the effects of shift work tend to use correlation methods

-this means it is difficult to establish whether desynchronization of the sleep/wake cycle is actually a cause o negative effects

-Solomon concluded that high divorce rates in shift workers might be due to the strain of deprived sleep and other influences such as missing out on important events

STRENGTH: it has been used to improve medical treatments

-circadian rhythms coordinate a number of the body's basic processes such as heart rate , digestion and hormone level s

-rise and fall during the course of a day which has led to the field of chronotherapeutics (how medical treatment can be administered in a way that corresponds to a persons biological rhythms)

-aspirin as a treatment for heart attacks is most effective if taken last thing at night

-reduces blood platelet activity and this can reduce the risk of heart attack

-heart attacks are most likely to occur early it the morning so timing matters

LIMITATION: generalisations are difficult to make

-studies are based on a very small samples of participants it seems that sleep wake cycles may vary widely from person to person

- Czeisler et al found individual differences in sleep/wake cycles from 13 to 65 hours and Duffy et al found some people naturally prefer early bed/awake

define infradian rhythms

A type of biological rhythm with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder.

explain infradian rhythms in terms of the menstrual cycles

-the menstrual cycle is governed by monthly changes in hormone levels which regulate ovulation

-cycle refers to the time between first day of a woman's period when the womb lining is shed, to the day before her next period

-typical cycle takes approximately 28 days to complete

-during each cycle rising levels of the hormone oestrogen cause the ovary to develop an egg and release it

-after ovulation the hormone progesterone helps the womb lining to grow thicker, readying the womb for pregnancy

-if pregnancy does not occur, egg is absorbed into the body, womb lining comes away and leaves the body

describe synchronising the menstrual cycle (and research)

-the cycle is an endogenous system, evidence suggests it may be influenced by exogenous factors such as cycles of other women

-Stern and McClintock demonstrated how menstrual cycles may synchronise as result of the influence of pheromones

-Stern and McClintock studies 29 women with a history of irregular periods, samples of pheromones were gathered from nine of the woman at different stages of their menstrual cycle via a cotton pad placed in their armpit

-the pads were worn for at least 8 hours to ensure pheromones were picked up

-pads treated with alcohol and frozen to be rubbed on upper lip of other ppts , one day one pads from the start of the menstrual cycle were applied to all 20 women on day 2 they were all given a pad from the second day of their cycle and so on

-they found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their 'odour donor'

describe seasonal affective disorder as an infradian rhythm

-a depressive disorder which has a seasonal pattern of onset and is described and diagnosed as a mental disorder

-main symptoms are persistent low mood and general lack of activity and interest in life

-'winter blues' as symptoms are triggered during the winter months when the number of daylight hours get shorter

-type of infradian rhythm called a circannual rhythm as it is subject to a yearly cycle, can also be classed as a circadian rhythm as experience of SAD may be due to the disruption of sleep/wake cycle and can be attributed to prolonged period of daily darkness during winter

-hormone melatonin is implicated in the cause of SAD during the night, the pineal gland secretes melatonin until dawn when there is an increase in light

-during winter, lack of light in the morning means the secretion process continues for longer, thought to have a knock on effect on the production of serotonin in the brain

define ultradian rhythms

A type of biological rhythm with a frequency of more than one cycle in 24 hours

explain ultradian rhythm of the sleep cycle

-identified 5 distincts stages of sleep that altogether span 90 minutes , a cycle that continues through the night

-each stage is characterised by a different level of brainwave activity which can be monitored using an EEG

-Stages 1 and 2: this is a light sleep where a person may be easily woken. In stage 1, brain waves are high frequency and have a short amplitude-these are alpha waves, in stage 2 the alpha waves continue but there are occasional random changes in pattern called sleep spindles

-stages 3 and 4 this is known as deep sleep or slow wave sleep (SWS) the brain waves are delta waves with lower frequency and higher amplitude, difficult to wake someone

-stage 5 (REM sleep) the body is paralysed yet brain activity closely resembles that of awake brain, during this time the brain produces theta waves and the eyes occasionally move around, thus rapid eye movement (REM) dreams often experienced

evaluate menstrual cycle synchronisation as an infradian rhythm

STRENGTH: may be explained by natural selection

-our distant ancestors it may have been advantageous for women to menstruate together and become pregnant at the same time, this would allow babies who had lost their mothers during or after childbirth to have access to breast milk, improving chances of survival

-suggests synchronisation is an adaptive strategy

LIMITATION: methodological shortcomings

-many factors that may effect change to the menstrual cycle, including stress, changes in diet, exercise

-these may act as confounding variables which means that any supposed pattern of synchronisation is no more than would have been expected to occur by chance

-other studies have failed to replicate their findings

evaluate sleep cycles as ultradian rhythms

STRENGTH: improved understanding of age-related changes in sleep

-sleep scientists have observed that SWS reduces with age , growth hormone is produced mostly during SWS therefore this is reduced in older people

-Cuater et al, resulting sleep deficit may explain various issues in old age, such as reduced alertness

-to increase SWS, relaxation and medication may be used

-suggests that knowledge of ultradian rhythms has practical value

LIMITATION: ultradian rhythms research is there is significant variation between people

-Tucker et al found large differences between participants in terms of duration of each sleep stage, particularly 3 and 4

-Tucker et al suggest that these differences are likely to be biologically determined, makes it difficult to describe 'normal sleep' in any meaningful way

Define an endogenous pacemaker

internal body clocks that regulate many of our biological rhythms such as influence of the suprachiasmatic nucleus on the sleep/wake cycle

explain the suprachiasmatic nucleus in terms of endogenous pacemakers and the sleep/wake cycle

-the suprachiasmatic nucleus (SCN) is a tiny bundle of nerve cells located in the hypothalamus in each hemisphere of the brain

-it is one of the primary endogenous pacemakers in mammalian species and is influential in maintaining circadian rhythms such as sleep/wake cycle

-nerve fibres connected to the eye cross in an area called the optic chiasm on their way to the left and right visual area of the cerebral cortex

-the SCN lies just above the optic chasm

-recieves info about light directly from this structure, continues even when our eyes are closed enabling the biological clock to adjust to changing patterns of daylight whilst we are asleep

explain how animal studies and the SCN work in terms of the endogenous pacemakers and the sleep/wake cycle

-DeCoursey et al destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat and observed for 80 days

-the sleep/wake cycle of the chipmunks disappeared and by the end of the study a significant proportion of them had been killed by predators

-Ralph et al bred 'mutant' hamsters with a 20hour sleep/wake cycle when SCN cells from foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cycles of the second group defaulted to 20 hours

explain the pineal gland and melatonin

-the SCN passes the info on day length and light that it receives to the pineal gland

-this is another endogenous mechanism guiding the sleep/wake cycle

-during the night, the pineal gland increases production of melatonin - a chemical that induces sleep and is inhibited during periods of wakefulness, melatonin has been suggested as a casual factor in SAD

Define exogenous zeitgebers

External cues that may affect or entrain our biological rhythms

describe light as an exogenous zeitgeber

-light is a key zeitgeber in humans, it can reset the body's main endogenous pacemaker, the SCN and plays role in maintenance of sleep/wake cycle

-light has an indirect influence on key processes in the body that control such functions as hormone secretion and blood circulation

-Campbell and Murphy demonstrated that light may be detected by skin receptor sites on the body even when same info not received by eyes

-15 participants were woken at various times and a light pad shone on back of knees

-the researchers managed to produce a deviation in the participants usual sleep/wake cycle of up to 3 hours in some cases

describe social cues as exogenous zeitgebers

-babies are seldom on the same sleep/wake cycle as the rest of the family in fact newborn babies initial cycle is mostly random

-at 6 weeks of age , the circadian rhythms begin and by 16 weeks babies rhythms have been entrained by the schedules imposed by parents, including adult determined mealtimes and bed times

-research on jet lag suggests that adapting to a local times for eating and sleeping is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances

evaluate endogenous pacemakers

LIMITATION: may obscure other body clocks

-research has revealed that there are numerous circadian rhythms in many organs and cells in the body

-these peripheral oscillators are found in the organs, including lungs pancreas and skin

-influenced by the actions of SCN but also independently

-Damiola et al demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the liver up to 12 hours whilst leaving the rhythm of the SCN unaffected

LIMITATION: endogenous pacemakers cannot be studied in isolation

-total isolation studies such as Siffre's cave study are extremely rare

-Siffre made use of artificial light which could have reset his body clock every time he turned his lamp on

-in everyday life, pacemakers and zeitgebers interact and it may make little sense to separate the two for purpose of research

evaluate exogenous zeitgebers

LIMITATION: exogenous zeitgebers do not have the same effect in all environments

-experience of people who live in places where there is very little darkness in summer and very little light in the winter tell a different story

-people who live in Arctic Circle have similar sleep patterns all year round despite spending 6 months in darkness

-sleep/wake cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light

LIMITATION: evidence challenges the role of exogenous zeitgebers

-Miles et al recount the study of a young man, blind from birth, who had an abnormal circadian rhythm of 24.9 hours despite exposure to social cues such as regular mealtimes, his sleep/wake cycle could not be adjusted