Paper 2 - Biopsychology Flashcards
What is the nervous system
A specialised network of cells and the primary communication system in the body
What are the two main functions of the nervous system
To collect, process and respond to information in the environment.
To coordinate the working of different organs and cells in the body.
What is the nervous system divided into
The central nervous system and the peripheral nervous system
What is the central nervous system
Consists of the brain and spinal cord and is the origin of all complex commands and decisions
What is the peripheral nervous system
Sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body via millions of neurons
What is the outer layer of the brain called
The cerebral cortex
What is the cerebral cortex
The surface layer of the forebrain (the two hemispheres). It is grey in colour and is highly folded to make it possible to fit the massive amount of material inside the skull
What distinguishes our higher mental functions from those of animals
The cerebral cortex as it’s highly developed
What is the spinal cord responsible for
It’s an extension of the brain and is responsible for reflex actions. It passes messages to and from the brain and connects nerves to the PNS
What is the PNS subdivided into
The autonomic nervous system and the somatic nervous system
What is the autonomic nervous system
Transmits information to and from internal bodily organs. It is autonomic as the system operates involuntarily. It has two main divisions: the sympathetic and parasympathetic nervous systems
What vital functions does the ANS govern
Breathing, heart rate, digestion, sexual arousal and stress response
What is the somatic nervous system
Transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act
What is the endocrine system
One of the body’s major communication system that instructs glands to release hormones directly into the bloodstream. These hormones are carried towards target organs in the body.
What does the endocrine system release
Hormones. It works much slower than the nervous system but has widespread and powerful effects
What is a gland
An organ in the body that synthesises biochemical substances such as hormones
What produces hormones
Glands
What is a hormone
Biochemical substances that circulate in the bloodstream and control and regulate the activity of certain cells or organs. Hormones only affect target organs. They are produced in large quantities but disappear quickly. Their effects are very powerful
What is the major endocrine gland
The pituitary gland, located in the brain
What is the pituitary gland
Called the master gland of the body’s hormone system because it controls the release of hormones from all the other endocrine glands in the body
What do hormones do
They get secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone
Example of of a hormone
Thyroxine produced by the thyroid gland affects cells in the heart and also cells throughout the body which increases metabolic rates. This in turn affects growth rates
What do the endocrine system and the autonomic nervous system work together to produce
The fight or flight response
What is the fight or flight response
The way an animal responds when stressed. The body becomes physiologically aroused in readiness to fight an aggressor or in some cases flee
How do the endocrine system and the ANS work to produce the fight or flight response
When a stressor is perceived, the hypothalamus triggers activity in the sympathetic branch of the ANS. the ANS changes from its testing state (the parasympathetic state) to physiologically aroused sympathetic state.
The stress hormone adrenaline is released from the adrenal medulla into the blood stream.
Adrenaline triggers physiological changes in the body e.g increased heart rate known as the fight or flight response.
What happens during the fight or flight response once’s the threat has passed
The parasympathetic nervous system returns the body to its resting state. This acts as a ‘brake’ and reduced the activities of the body that were increased by the actions of the sympathetic branch
What is the parasympathetic response after the fight or flight response sometimes referred to as
The ‘rest and digest’ response
What is adrenaline
A hormone produced by the adrenal glands. These are part of the human body’s immediate stress response. Adrenaline has a strong effect on the cells of the cardiovascular system - stimulating the heart rate, contracting blood vessels and dilating air passages
What is the hypothalamus
A small subcortial brain structure which plays a major role in the body’s stress response and maintaining a state of balance (homoeostasis) by regulating many of its key processes such as heart rate and body temperature. The lateral hypothalamus (LH) and the ventro-medial hypothalamus (VMH) start and stop eating
What are endocrine glands
A group of organs in the body that release hormones into the blood stream
How many neurons are in the human nervous system
100 billion
What percentage of all neurons in the nervous system reside in the brain
80%
What two ways do neurons transmit signals
Electrically and chemically
What are the three types of neurons
Motor
Sensory
Relay
What do motor neurons do
Carry messages from the CNS to effectors such as muscles and glands.
Short dendrites and long axons.
What are dendrites
Branching projections from the end of a neuron that carry nerve impulses from neighbouring neurons towards the cell body
What are axons
The long projection of the neuron from the cell body
What do sensory neurons do
Carry messages from the PNS to the CNS.
Long dendrites and short axons.
What do relay neurons do
Connect sensory neurons to motor neurons or other relay neurons.
Short dendrites and short axons.
What is a neuron
The basic building blocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals
What is the basic structure of a neuron
The cell body (soma) has a nucleus.
Branch-like structure called dendrites from the cell body.
The axon covered in a fatty layer of myelin sheath.
Gaps in the sheath called nodes of Ranvier.
End of the axon has terminal buttons.
What is the purpose of a nucleus
It contains the genetic material of a cell and is the control centre of a cell
What is the purpose of dendrites
They carry nerve impulses from neighbouring neurons towards the cell body
What is the purpose of the axon
Carries the electrical impulse away from the cell body down the length of the neuron
What is the purpose of the myelin sheath
To protect the axon and speed up electrical transmission
What is the purpose of nodes of Ranvier
To speed up the transmission of the impulse
What is the purpose of terminal buttons
They communicate with the neighbouring neuron by releasing neuron transmitters across the synapse
When a neuron is in a resting stage, what is the inside of the cell compared to the outside
Negatively charged
How does an action potential occur
When a neuron is activated, the inside of the cell becomes positively charged for a split second causing an action potential
What is an action potential
A short increase and decrease of electrical activity in the membrane of a neuron, transmitting a signal away from the cell body.
What does an action potential in a neuron create
an electrical impulse that travels down the axon towards the end of the neuron.
What is each neuron separated by
A tiny gap called the synapse
What is the synapse
The gap between the postsynantic and presynaptic neuron
What is the difference between signals transmitted within the neuron and those transmitted across the synapse
Within the neuron the signals are transmitted electrically but between each neuron they are diffused chemically
When the electrical impulse reaches the presynaptic terminal, what does it trigger
The release of neurotransmitters from tiny sacs called synaptic vesicles
What is the presynaptic terminal
The end of the transmitting neuron, ending at a synapse
What is a neurotransmitter
Brian chemicals released from synaptic vesicles that relay signal across the synapse from one neuron to another
What are synaptic vesicles
Small sacs at the end of a presynaptic neuron that contain neurotransmitters that will be released into a synapse
When a neurotransmitter has crossed the synapse, what happens
It is taken up by the postsynaptic receptor sure in the next neuron. The chemical message is converted back into an electrical impulse and the process of transmission begins again
What is the postsynaptic receptor site
A receptor on the neuron that is receiving the information at the synapse. A neurotransmitter locks into a specific receptor on the receiving neuron and this triggers an electrical signal in the receiving neuron
What does each neurotransmitter have
It’s own specific molecular structure that fits perfectly into a postsynaptic receptor site
Example of a neurotransmitter
Acetylcholine (ACh) is round at each point where a motor neuron meets a muscle, causing muscles to contract
What effects can neurotransmitters have on neighbouring neurons
Excitatory or inhibitory effects
What is excitation
When a neurotransmitter, such as adrenaline, increases the positive charge of the post synaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse
What is inhibition
When a neurotransmitter, such as serotonin, increases the negative charge of the postsynaptic neuron. This decrease the likelihood that the neuron will fire and pass on the electrical impulse
What effects does dopamine have
Both inhibitory and excitatory effects in roughly equal measure
In the early 19h century, what did scientists believe of the brain
That all parts of the brain were involved in processing thoughts and actions - holistic theory.
After the 19th century, what was discovered about the brain
That specific areas of the brain were associated with particular physical and psychological functions - localisation theory. If a certain area of the brain becomes damaged through illness or injury, the function associated with that part will also be damaged .
What is localisation or function
The theory that different areas of the brain are responsible for different behaviours, processes or activities
What is hemispheric lateralisation
The idea that two halves (hemispheres) of the brain are functionally different and that certain mental processes and behaviours are mainly controlled t one hemisphere rather than the other as in the example of language (which is localised as well as lateralised)
What does the right hemisphere control
The left-hand side of the body
What does the left hemisphere control
The right-hand side of the body
How thick is the cerebral cortex
3mm
Why does the cerebral cortex appear grey
Due to the location of cell bodies
What is the cortex of both hemispheres divided into
Frontal
Parietal
Occipital
Tempeotal
What is the frontal lobe
Area of the brain responsible for logical thinking and making decisions
Where is the motor cortex
At the bad of the frontal lobe
What does the motor area control
Voluntary movement on the other side of the body.
What may damage to the motor area result in
A loss of control over fine motor movements
Where is the somatosensory area
At the front of both parietal lobes
What is the somatosensory area
It’s where sensory information from the skin (related to touch, heat, pressure etc) is represented.
What denotes a body parts sensitivity
The amount of somatosensory area devoted to a particular body part
Where is the visual area
In the occipital lobe at the back of the brain
What is the visual area/ cortex
A part of the occipital lobe that receives and processes visual information
How does each eye process information
Each eye sends information from the right visual field to the left visual cortex, and from the left visual field to the right visual cortex
What can damage to the left hemisphere result in
Blindness in part of the right visual field in both eyes
What is the auditory area
The temporal lobe
What is the auditory area
Located in the temporal lobe and concerned with the analysis of speech-based information
What will damage in the auditory area produce
Hearing loss
What did BROCA identify
A small area in the left frontal lobe responsible for speech production - Broca’s area
What may damage to Broca’s area result in
Broca’s aphasia which is characterised by speech that is slow, laborious and lacking in fluency.
What may people with brocas aphasia experience
Difficulty finding words and naming certain objects. They may also have difficulty using prepositions and conjunctions - small words that link sentences such as ‘a’, ‘the’ or ‘and’
What did WERNICKE identity
An area in the back of the temporal lobe (encircling the auditory cortex) in the left hemisphere called Wernickes area responsible for language comprehension
What happens to patients with damage to wernickes
They have no problem producing language but severe difficulties understanding it, such that the speech they produced was fluent but meaningless
What do patients who have Wernickes aphasia produce
Nonsense words (neologisms) as part of the content of their speech
What are 2 strengths of support localisation theory
Brain scan evidence to support the theory. Wealth of evidence supporting the idea that many neurological functions are localised, particularly in relation to language and memory. A study of long-term memory by TULVING revealed that semantic and episodic memories are located in different parts of the frontal cortex. The use of the objective and sophisticated brain scans provide evidence for localisation of brain function.
Supporting evidence from case studies. Phineas Gage who received serious brain damage by accident. Gage survived but the damage to his brain affected his personality. He went from someone who was calm and reserved who was quick tempered, rude and ‘no longer Gage’. The change in Gage’s temperament following the accident suggests that the frontal lobe may be responsible for regulating mood.
2 limitations of the localisation theory
Existence of contradictory research. LASHLEY suggests that higher cognitive functions, such as the processes involved in learning, are not localised but distributed in a more holistic way. He removed the areas of the cortex (10-50%) in rates learning a maze. No area was shown to be more important than any other in terms of the data ability to learn the maze. Seems to need all of the cortex rather than being confined to a particular area. Suggests learning is too complex to be localised and requires the involvement of the whole of the brain.
Neural plasticity is a challenge to the theory. Cortical remapping our neural plasticity where the brain has been damaged, and a particular function has been compromised or lost, the rest of the brain appears able to reorganise itself in an attempt to recover the lost function. LASHLEY described it as the law of equipotentiality where by surviving brain circuits ‘chip in’ so the same neurological action can be achieved. Does not happen everytime but there are several documented cases of strike victims being able to recover abilities that were seemingly lost.
What is brain plasticity
Also referred to as neuroplasticity or cortical remapping. This describes the brains tendency to change and adapt (functionally and physically) as a result of experience and new learning
What did GOPNIK say happens during infancy (brain plasticity)
The brain experiences a rapid growth in synaptic connections, peaking at approximately 15,000 at age 2-3
What is synaptic transmission
The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (the synapse) that separates them
What is synaptic pruning in plasticity
As we age, rarely used connections are deleted and frequency used connections are strengthened
What has recent research into neural connections and plasticity suggested
That they can change or be formed at any time in life, as a result of learning and experience - not restricted to childhood
Who studied plasticity
MAGUIRE
DRAGANSKI
What did MAGUIRE find
Studied the brains of London taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than a matched control group.
As part of their training London cabbies must take a test called ‘The Knowledge’ which assesses their recall of the city streets and possible routes.
It appears that this learning experience alters the structure of the taxi drivers brains. The longer they had been in the job, the more pronounced the structural difference.
What does the hippocampus do
It is associated with the development of spatial and navigational skills
What did DRAGANSKI find
He imaged the brains of medical students three months before and after their final exams. Learning-induced changes were seen to have occurred in the posterior hippocampus and the parietal cortex, presumably as a result of the exam
What is the hippocampus
A structure in the subcritical area of each hemisphere of the forebrain, associated with memory. It is part of the limbic system, and is therefore also involved in motivation, emotion and learning
Example of neural plasticity
Functional recovery
What is functional recovery
A form of plasticity. Following damage through trauma, the brains ability to redistribute or transfer functions usually performed by a damaged, destroyed or even missing area to an undamaged one
What do neuroscientists suggest about functional recovery
It can occur quickly after trauma (spontaneous recovery) and then slows down- at which point the person may require rehabilitative therapy
How does the brain ‘rewire’ itself in functional recovery
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
Besides forming new synaptic connections, what are other structural changes that may occur after trauma
Axonal sprouting.
Reformation of blood vessels.
Recruitment of homologous (similar) areas on the opposite side of the brain to perform specific tasks.
What is axonal sprouting
The growth of new nerve endings which connects with other undamaged nerve cells to form new neuronal pathways
2 strengths of neural plasticity
Practical application. Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation. Techniques may include movement therapy and electrical stimulation of the brain to counter the deficits and/or cognitive functioning that may be experience following, say, a stroke. Shows that, although the brain may have the capacity to ‘fix itself’ to a point, the process requires further intervention if its to be successful.
Support for neural plasticity from animal studies. Early evidence of neural plasticity and functional recovery was derived from animal studies. WIESEL and HUBEL sewed one eye of a kitten shut and analysed the brains cortical responses. Found that the area of the visual cortex associated with the shut eye was not idle (as predicted) but continued to process information from the open eye. This pioneering study demonstrates how a loss of function leads to compensatory activity in the brain - evidence of neural plasticity.
2 limitations of neural plasticity
Potential negative consequences. Brains ability to rewire itself can sometimes have maladaptive behavioural consequences. 60-80% of amputees develop phantom limb syndrome - the confined experience of sensations in the missing limb as if it were still there. These sensations are unpleasant, painful and are thought to be due to reorganisation in the somatosensory cortex. Such evidence suggests that the structural and physical processes involved in functional recovery may not always be beneficial.
Cognitive reserve affects neural plasticity. Evidence suggests that a person educational attainment may influence how well the brain functional adapts after injury. SCHNEIDER discovered the more time brain injury patients spent in education - taken as an indication of their cognitive reserve - the greater their chances of a disability-free recovery (DFR). 2/5s of patients studied who achieved DFR had more than 16 years education compared to about 10% of patients who had less than 12 years. Suggests that cornice reserve is a crucial factor in determining how well the brain adapts after a trauma.
Example of hemispheric lateralisation
The ability to reproduce and understand language
For most people, which hemisphere controls language
The left
What is split-brain research
A series of studies which began in the 1960s (and are still ongoing) involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. This allowed researchers to investigate the extent to which brain function is lateralised
What was investigated by SPERRY and his colleagues
The question of whether other neural processes besides language are organised through hemispheric lateralisation
What did SPERRYs study involve
Participants who had undergone the same surgical procedure - a commisurotomy.
In this operation the corpus callosum which connects the two hemispheres is cut to control epileptic seizures. The consequence is that the hemispheres can no longer communicate so act like two separate brains.
This allowed SPERRY to see the extent to which the two hemispheres were specialised for certain functions, and the extent to which the hemispheres performed tasks independently of one another.
What was the procedure of SPERRYs study
An image or word could be projected to a patients right visual field (processed by the left hemisphere) and the same, or different, image could be projected to the left visual field (processed by the right hemisphere).
In the normal brain, the corpus callosum would immediately ‘share’ the information between both hemispheres, giving a complete picture of the visual world. In the split brain, the information could not be conveyed from the chosen hemisphere to the other.
Findings of SPERRYS study (describing what was seen)
When a picture of an object was shown to a patients right visual field, they could easily describe what was seen.
However, if the picture was shown to the left visual field the patient could not describe what was seen.
Patients inability to describe the object in the left visual field (processed by the right hemisphere) is because of the lack of language centres in the right hemisphere in most people. In a normal brain the messages received by the right hemisphere would be replayed via the corpus callosum to the language centre in the left hemisphere
Findings of SPERRYs study (recognition by touch)
Although patients could not attach verbal labels to objects projected in the left visual field, they were able to select a matching object group a grab-bag of different objects using their left hand (connected to the right hemisphere which receives information from the left visual field). The objects were placed behind a screen so as not to be seen.
The left hand was able to select an object that was most closely associated with an object presented to the left visual field - for instance an ash tray when shown a cigarette.
In each case, the person was not able to verbally identity what they had seen (bc left hemisphere is needed for this) but could nevertheless ‘understand’ what the object was using the right hemisphere and select the corresponding object accordingly.
Findings of SPERRYs study (composite words)
Two words presented simultaneously, one on either side of the visual field. For example, ‘key’ presented to the left and ‘ring’ to the right, the patient would select a key with their left hand (left hand goes to the right hemisphere linked to the left visual field) and say the word right (right visual field linked to the left hemisphere).
Findings of SPERRYs study (matching faces)
Right hemisphere seems to be dominant.
When asked to match a face from a series of other faces, the picture processed by the right hemisphere (left visual field) was consistently selected. When a composite picture made up of two different halves of a face was presented (one half to each hemisphere) the left hemisphere dominated in terms of verbal description whereas the right hemisphere dominated in terms of selecting a matching picture
What is the left hemisphere more geared towards
Analytics and verbal tasks (the analyser)
What is the right hemisphere more adept at
Performing spatial tasks and music (the synthesiser)
2 strengths of SPERRYs study
Methodology. Made use of highly specialised and standardised procedures. Participants asked to stare at a fixed point, whilst one eye was blindfolded. The image projected would be flashed up for one tenth of a second, meaning the patient would not have time to move their eye across the image and spread the information across both sides of the visual field, and subsequently, both sides of the brain. This allowed SPERRY to vary aspects of the basic procedure and ensure that only one hemisphere was receiving information at a time. Thus he developed a very useful and well controlled procedure.
Prompted a theoretical and philosophical debate about the nature of consciousness and the degree of communication between the two hemispheres in everyday functioning. Some suggest that the two hemispheres are so functionally different that they represent a form of duality in the brain - we are two minds. Others argue that the two hemispheres are a highly integrated system and work together during most tasks. The value of SPERRYs work is in prompting this complex debate
2 limitations of SPERRYs research
Issues with generalisation. Many researchers have said it can’t be widely accepted as split-brain patients are such an unusual sample of people. There were only 11 patients who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures. It has been argued that this may have caused unique changes in the brain and influenced the findings. This limits the extent to which the findings can be generalised to normal brains, reducing validity.
May have overstated the differences in function between the two hemispheres. One legacy of SPERRYs work is a growing body of pop-psychological literature that oversimplifies and overstates the difference in function between the left and right hemispheres. Although the ‘verbal’ and ‘non-verbal’ labels can be useful to apply to summarise the differences in hemispheres, modern neuroscientists would argue that the distinction is actually a lot less clear-cut than this. Many of the behaviours typically associated with one hemisphere can be effectively performed by the other when the situation requires it. The apparent flexibility of the hemispheres suggests some of the conclusions draw by SPERRY may be too simplistic.
What are techniques for investigating the brain often used for
Medical purposes in the diagnosis of illness and to investigate localisation - in other words to determine which parts of the brain do what
What are the 4 ways of scanning the brain
FMRI
EEGs
ERPs
Post mortem examinations
What are FMRIs
A method used to measure brain activity while a person is performing a task that uses MRI technology (detecting radio waves from changing magnetic fields).
How do FMRIs work
It detects changes in blood oxygenation and flow that occurs due to neural activity in specific areas. When a brain area is more active it consumes more oxygen and blood flow is directed to the active area (haomodynamic resoonse). It produces a 3D image showing which parts of the brain are involved in particular mental processes.
What is a haemodynamic response
When an area it active and consumes more oxygen and blood flow is directed to the active area
What are EEGs
Electrodes are attached to a persons scalp using a skull cap to record the tiny electrical impulses produced by the brains activity. By measuring characteristics wave patterns, the EEG can help diagnose certain conditions of the brain
What does the scan recording of EEG represent
Overall brain activity - the brain wave patterns generated from millions of neurons
What is EEG often used as
A diagnosis tool
What may unusual arrhythmic patterns of brain activity identified from EEGs indicate
Abnormalities such as epilepsy, tumours or sleep disorders
What are ERPs (event related potentials)
The brains electrophysiological response to a specific sensory, cognitive or motor event can be isolated through statistical analysis of EEG data. They leave only the responses that relate to, say, the presentation of a specific stimulus or performance of a certain task
What are event related potentials
Types of brainwaves that are triggered by particular events
What has research revealed about ERPs
There’s many different forms and how they are linked to cognitive processes such as perception and attention
What is a post-mortem examination
The brain is analysed after death to determine whether detain observed behaviours (disorders or deficits) during the patients lifetime can be linked to abnormalities in the brain
What may be included in post mortem examinations
Comparison with a neurotypical brains
Strengths and limitations of FMRI
Strength: non-invasive. Unlike other scanning techniques like PET, it does not rely on the ingestion of radiation and is safe. It also produced images that have a very high spatial resolution, showing detail to the millimetre. This means it can provide a clear picture of how brain activity is localised.
Weakness: expensive compared to other techniques. Can only capture a clear image if the person stays still. It also has poor temporal resolution because there is a 5 second time lag behind the image on screen and the initial firing of neural activity. This means it may not truly represent moment-to-moment brain activity.
Strengths and limitations of EEGs
Strength: proved invaluable in diagnosing conditions like epilepsy. Also contributed to our understanding of the stages involved in sleep. Has extremely high temporal resolution. Today’s EEG technology can accurately detect brain activity at a resolution of a single millisecond.
Weakness: the generalised nature of the information received (that of many thousands of neurons) as the signal is not useful in pinpointing the exact source of neural activity. It is difficult to know the exact source. It does not allow researchers to distinguish between activity coming from different but adjacent locations.
Strengths and limitations of ERPs
Strengths: provide very specific measurements of neural processes. They are much more specific than could ever be achieved using raw EEG data. They had excellent temporal resolution, especially when compared to other neuroimaging techniques like FMRI and this had led to their widespread use in the measurement of cognitive functions and deficits.
Weaknesses: lack of standardisation in ERP methodology between different studies, makes it difficult to confirm findings in studies involving ERPS. In order to establish pure data in ERP studies, background noise and extraneous materials much be eliminated which isn’t always easy:
Strengths and limitations of post mortems
Strengths: they were vital in producing a foundation for early understanding of key processes in the brain e.g Einstein. BROCA and Wernicke relied on post mortem studies in establishing links between language, brain and behaviour. Improve medical knowledge which helps generate hypotheses for further study.
Weaknesses: causation may be an issue, observed damage in the brain may not be linked to the deficits under review but to some other related trauma or decay. Ethical issues of consent from the patient before death as patients may not be able to provide informed consent, for example HM lost his ability to form memories and wasn’t able to provide such consent yet post mortem were still conducted on his brain.
What is a PET scan
Positron emission tomography. A brain scanning method used to study activity in the brain. Radioactive glucose is ingested and can be detected in the active areas of the brain
What is a biological rhythm
distinct patterns of changes in body activity that conform to cyclical time periods. They are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers)
What are ultradian rhythms
A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep
What is an infradian rhythm
A type of biological rhythm with a frequency of less than one cycle in 24 hours such as menstruation and seasonal affective disorder
What is the sleep/wake cycle
A daily cycle of biological activity based on a 24-hour period (circadian rhythm) that is influenced by regular variations in the environment, such as the alternation of night and day
How is the sleep/wake cycle government by exogenous zeitgebers
The fact we feel drowsy when it’s night-time and alters during the day shows the effects of daylight
How is the sleep/wake cycle government by endogenous pacemakers
If the biological clock is ‘left to its own devices’, without the influence of internal stimuli, it is called ‘free-running’. Research shows there is a basic rhythm government by the suprachiasmatic nucleus.
Who did experiments of the sleep/wake cycle
Michael SIFFRE
What did SIFFRE do
A series of unusual experiments where he spent long periods of time in dark caves to examine the effects of free-running biological rhythms. Deprived of exposure to natural light and sound but with access to food and water, SIFFRE resurfaced after 2 months in the cave. He later performed a similar experiment for 6 months in a Texan cave.
Findings of SIFFREs experiment
His free-running circadian rhythm settles down to one that was just beyond the usual 24hours (around 25), though he did continue to fall asleep and wake up on a regular basis
What did ASCHOFF and WEVER find
That a group of participants that spent 4 weeks in a World War 2 bunked deprived of natural light. All but one of the participants (whose sleep/wake cycle extended to 29 hours) displaced a circadian rhythm between 24 and 25 hours
Why is the sleep/wake cycle entrained by exogenous zeitgebers
Because studies suggest our natural sleep/wake cycle is longer than 24 hours but because of environmental factors associated with our days we can’t (such as the number of daylight hours, typical mealtimes)
What did FOLKARD find
Studied a group of 12 people who lived in a dark cave for 3 weeks, retiring when the clock said 11:45pm and rising when it said 7.45am. Over the course of the study, the researcher gradually speeded up the clock (unbeknown to the participants) so an apparently 24 hour day only lasted 22.
One of the participants was even able to comfortably able to adjust to the new regime.
What are the conclusions of FOLKARDs study
Suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by changes in the external environment
2 strengths into research into circadian rhythms
Practical application into shift work. Knowledge of circadian rhythms have given researchers a better understanding of the adverse consequences that can occur as a result of their disruption (desynchronisation). BOIVIN found that shift workers experienced a period of reduced concentration around 6am (a circadian trough) meaning mistakes and accidents are more likely. Thus, research into the sleep/wake cycle may have economic implications in terms of how to best manage workers productivity.
Practical application to drug therapy. Circadian rhythms coordinate a number of the body’s basic processes such as heart rate, digestion and hormone levels. This in turn had an effect on pharmocokinetics, that is, the action of drugs on the body and how well they are absorbed and distributed. Research into circadian rhythms have revealed that there are certain peak times during the day or night when drugs are likely to be more effective which has led to the development of guidelines to do with the timing of drug dosing. Therefore research into circadian rhythms may have real life medical benefits.
2 limitations of research into circadian rhythms
Use of case studies and small samples in studies. Studies into the sleep/wake cycle tend to involve small groups, as in the case of WEVER, or case studies of single individuals, SIFFRE. The people involved may not represent the whole population and this limits the extent to which generalisations can be made. In most recent cave experience, SIFFRE found that at the as of 60 his body clock ticked more slowly than when he was young showing how there are factors that prevent general conclusions, like age.
Poor control in research studies. The participants in studies were deprived of natural light but still had artificial light. E.g SIFFRE turned on a lamp every time he woke up which remained on until he slept again. It was assumed that the artificial light would have no effect on the biological rhythm. However studies have been able to adjust participants circadian rhythms from 22 hours to 28 using dim lighting. This suggest that researchers may have ignored an important confounding variable in circadian rhythm research.
Example of infradian rhythm
Female menstrual cycle
Seasonal affective disorder (SAD)
What is the female menstrual cycle
Governed by monthly changes in hormone levels which regulate ovulation. The typical cycle takes approximately 28 days to complete
What is the process of the menstrual cycle
During each cycle, rising levels of estranged cause the ovary to develop an egg and release it (ovulation). After ovulation, the hormone progesterone helps the womb lining to grow thicker, readying the body for pregnancy. If pregnancy does not occur, the egg is absorbed into he body and the womb lining comes away and leaves the body (menstruated flow)
What did STERN and McCLINTOCK do
Study involving 29 women with a history of of irregular periods. Samples of pheromones were taken from nine of the women at different stages of their cycle, via a cotton pad placed under their armpit. The pads were rubbed on the upper lip of the other participants. On day 1, 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, and so on.
What was the findings of STERN and McCLINTOCKs study
68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’. This suggests that the menstrual cycles may synchronise due to exogenous zeitgebers.
What is seasonal affective disorder
A depressive disorder which has a seasonal pattern of onset. As with other forms of depression, the main symptoms are persistent low mood and a general lack of activity and interest in life.
Why is seasonal affective disorder sometimes referred to as the ‘winter blues’
Because the symptoms are triggered during the winter months when the number of daylight hours become shorter.
What kind of infradian rhythm is SAD
A circannual rhythm as it is subject to a yearly cycle
What is melatonin
A hormone produced by the pineal gland that increases sleepiness. In humans it is usually produced at night and is regulated by the suprachiasmatic nucleus
How is the hormone melatonin implicated in the cause of seasonal affective disorder
During the night, the pineal gland secretes melatonin until dawn when there is an increase in light. During winter, the lack of light in the morning means this secretion process goes on for longer. This is thought to have a knock-on effect on the production of serotonin in the brain (low serotonin in linked to symptoms of depression)
What is an example of an ultradian rhythm
The stages of sleep
How long do the distinct stages of sleep take altogether
Approximately 90 minutes that continue throughout the course of the night
What is an ultradian rhythm
A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep
What is each stage of sleep characterised by
A different level of brainwave activity which can be monitored using an EEG
How many stages of sleep is there
5
What are stages 1 and 2 of the sleep cycle
Light sleep where the person may be easily woken. At the beginning of sleep, brainwave patterns start to become slower and more rhythm (alpha waves), becoming even slower as sleep becomes deeper (beta waves)
What are stages 3 and 4 of the sleep cycle
Involve delta waves which are slower still and have a greater amplitude than earlier wave patterns. This is deep sleep or slow wave sleep and it is difficult to rouse someone at this point.
What is involved in stage 5 of the sleep cycle
REM sleep, the body is paralysed yet brain activity speeds up significantly. R.E.M. stands for rapid eye movement to denote the fast, jerky activity of the eyes at this point
What is slow wave sleep
Also called deep sleep, a sleep stage during which growth hormones is secreted as well as other restorative activities. It is very difficult to wake someone up during this stage which occurs more at the start of the night than towards morning
2 strengths of infradian rhythms
Research into the menstrual cycle is that is demonstrates its evolutionary value.
Strength and two weaknesses of infradian rhythm research
Strength: research into menstural cycle demonstrates its evolutional value. For ancestors it may have been advantageous for females to menstruate together and fall pregnant around the same time so newborns could be cared for collectivity, increasing their chances of survival. It would appear to be an adaptive evolutionary strategy.
Limitation: methodology used in synchronisation studies. Commentators argue that many factors that effect the menstrual cycle includes stress and changes in diet etc which may be confounding variables. This means that any supposed pattern of synchronisation, in studies like MCCLINTOCKs, is no more than would have been expected to occur by chance. In addition, it involves a small sample of women and relies on self report which may be inaccurate. Suggest the important aspects of synchronisation studies may lack validity.
The use of animal studies. Much of the knowledge of the effects of pheromones on behaviour is derived from animal studies and the role of pheromones in animal sexual behaviour is well-documented. For instance, sea urchins release pheromones into the surrounding water so other urchins will eject their sex cells. In contrast, evidence for pheromones on human behaviour remains speculative and inconclusive.
Strength of research into ultradian rhythms
Strength: evidence supports the idea of qualitatively different stages in sleep. A landmark study by DEMENT monitored the sleep patterns of nine participants in a sleep lab. R.E.M. activity was highly correlated with the experience of dreaming, Brian activity varied according to how vivid dreams were, and participants woken up during dreaming reported very accurate recall of their dreams. Study suggests that R.E.M. sleep is an important component of the ultradian sleep cycle.
What is the suprachiasmatic nucleus
It lies just above the optic chiasm and receives information about light directly from this structure. Thus the exogenous zeitgeber (light) can reset the endogenous pacemaker
Strength of research into SAD
Practical application. One of the most effective treatments for SAD is phototherapy. This is a lightbox that simulates very strong light in the morning and evening. It is thought to reset melatonin level in people with SAD. This treatment relives symptoms in up to 60% of sufferers. However the same study recorded a placebo effect of 30% using a ‘sham negative-ion generator’ (participants told it was another form of treatment). This casts doubt on the real value of phototherapy, which may only be effective because of expectations
What are 3 endogenous pacemakers in the sleep/wake cycle
The suprachiasmatic nucleus
The pineal gland
Melatonin
Where is the SCN (suprachiasmatic nucleus)
The hypothalamus in each hemisphere
What is the SCN influential in
Maintaining circadian rhythms and it is the primary endogenous pacemaker
How does the SCN receive information about light
Nerve fibres connected to the eye cross in an area called the optic chiasm on their way to the visual area of the cerebral cortex. The SCN lies just above the optic chiasm and receives information directly from this structure
What did DeCOURSEY et al study
He destroyed the SCN connection in the brains of 30 chipmunks who were returned to their natural habitat and observed for 80 days. The sleep/wake cycle of the chipmunks disappeared and a significant proportion were killed by predators (because they were awake and vulnerable when they should have been asleep)
What did RALPH study
He bred ‘mutant’ hamsters with a 20-hour sleep/wake cycle. When SCN cells fein the foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cakes of the second group deflated to 20 hours. Both of these studies emphases the role of the SCN in establishing and maintaining the sleep/wake cycle.
How does the pineal gland and melatonin work as endogenous pacemakers
The SCN passes the information on day length and light that it receives to the pineal gland - a pea-like structure in the brain just behind the hypothalamus.
During the night, the pineal gland increases the production of melatonin - a chemical that induces sleep and is inhibited during periods of wakefulness.
What has been suggested as a causal faced of seasonal affective disorder
Melatonin
What is an endogenous pacemaker
Internal body clocks that regulate many of our biological rhythms
What are exogenous zeitgebers
External factors in the environment that reset our biological clocks through a process known as entrainment
Why does sleeping and wakefulness seem to be determined by an interaction of internal and external factors
In the absence of external cues, the free-running biological clock which controls the sleep/wake cycle continues to ‘tick’ in a district cyclical pattern
Examples of exogenous zeitgebers
Light
Social cues
How does light play a key role in the sleep/wake cycle
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a key role.
It also has an indirect influence on key processes in the body that controls such functions as hormone secretion and blood circulation
What did CAMPBELL and MURPHY study
They demonstrated that light may be detected by skin receptor sites on the body even when the same information has not been received by the eyes. 15 participants were woken at various times and a light pad was shine on the back of their knees.
The researchers managed to produce a deviation in the participants sleep/wake cycle of up to 3 hours in some cases. This suggests light is a powerful exogenous zeitgeber that need not necessarily rely on the eyes to exert influence on the brain.
How do social cues have an important influence on the sleep/wake cycle
In human infants, the sleep/wake cycle is pretty much random. At about 6 weeks, most babies are entrained. The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes
What does research suggest is an effective way of entraining circadian rhythms and tackling jet lag when travelling long distances
adapting to local times for eating and sleeping (rather than responding to ones own feelings of hunger and fatigue)
2 weaknesses of endogenous pacemakers
Research into the SCN may not take into account other body clocks. Research has revealed there are numerous circadian rhythms in many organs and cells in the body. These are call peripheral oscillators and are found in, for example, the lungs, liver, pancreas and skin. Although these peripheral clocks are highly influenced by the actions of the SCN, they can act independently. DAMIOLA demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the liver for up to 12 hours whilst leaving the rhythm of the SCN unaffected. Suggested that there may be many other complex influences on the sleep/wake cycle, aside from the master clock (the SCN).
The use of animals. Issue is generalising findings from research into the sleep/wake cycle from animal studies (issue of anthropomorphism). A more disturbing issue, particularly in DeCOURSEYs study is the ethics. The animals were exposed to considerable harm, and subsequent risk, when they were returned to their natural habitat. Whether what we learn from investigations such as these justifies the adverse procedures involved is a matter of debate.
What is the name of whether finding from non-human studies can be meaningfully applied to humans
Anthropomorphism
2 limitations of exogenous zeitgebers
Influence of exogenous zeitgebers May be overstated. A young man, blind from birth, had a circadian rhythm of 24.9 hours. Despite exposure to social cues, his sleep/wake cycle could not be adjusted and consequently had to take sedatives at night and stimulants in the morning to keep pace with the 24 hour world. Similar, studies of individuals who live in the Arctic region (where the sun does not set during the summer months) show normal sleep patterns despite the prolonged exposure to light. Both these examples suggest that there are occasions when exogenous zeitgebers have little bearing on our internal rhythms.
Methodological issues in research. CAMPBELL and MURPHY’s study has been critiqued and is yet to be replicated. One of these criticism is that there may have been limited light exposure to the participants eyes - a major confounding variable. Also, isolating one exogenous zeitgeber in this way does not give us insight into the many other zeitgebers that influence the sleep/wake cycle. Suggest that some studies may have ignored or underplayed the way in which different exogenous zeitgebers interact.
Limitation of both exogenous zeitgebers and endogenous pace makers
They interact. Only is exceptional circumferences are endogenous pacemakers free-running and unaffected by the influence of exogenous zeitgebers. Total isolation experiences, such as in SIFFREs cave study, are extremely rare and could be judged as presenting an unrealistic picture of how the system works. In real life, they interact and it may make little sense to separate the two for the purpose of research.
