Biopsychology Flashcards

Question

Describe the role of relay neurons

Answer 1

o Relay neurons are responsible for carrying information from one part of the CNS to the other. Relay neurons connect other neurons together (e.g. sensory to motor, or other relay neurons) o Relay neurons have sort dendrites and short axons

Answer 2

Impulses travel electrically down the pre-synaptic cell in vesicles containing neurotransmitters. When the electrical impulse reaches the end of the neuron, the presynaptic terminal, it triggers the release of neurotransmitters from synaptic vesicles. The neurotransmitters then chemically 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. Here, the chemical message is converted back into an electrical impulse and the process of transmission begins again in this other neuron. Neurotransmitters have either an excitatory or inhibitory effect on the neighbouring neuron. Excitation increases the probability that neurotransmitters will be released by the neuron and inhibition decreases the probability that neurotransmitters will be released by the neuron.

Answer 3

When a neuron sends an electrical message; this increases the probability that neurotransmitters will be released by the neuron- e.g. adrenaline

Answer 4

Inhibition is when a neuron fails to send an electrical message; this decreases the probability that neurotransmitters will be released by the neuron- e.g. serotonin

Answer 5

The idea that different parts of the brain perform different tasks and are involved with different parts of the body Therefore, if a certain area of the brain is damaged through illness or injury, the function associated with that area will also be affected

Answer 6

* The brain is divided into two symmetrical halves called the left and right hemispheres. * Some of our physical and psychological functions are controlled by a particular hemisphere- this is called lateralisation. * Activity on the right-hand side of the body is controlled by the left-hand side of the brain and vice versa e.g. language is linked to the left hemisphere

Answer 7

* The outer layer of both hemispheres is the cerebral cortex. * This is like a tea cosy covering the inner parts of the brain. * About 3mm thick, the cortex appears grey due to the appearance of cell bodies and dendrites; it is often referred to as ‘grey matter. * The cortex is divided into four lobes: the frontal lobe, the parietal lobe, the occipital lobe and the temporal lobe

Answer 8

- At the back of the frontal lobe is the motor area - Controls voluntary movement in the opposite side of the body - Damage to this area of the brain may result in a loss of control over fine movements

Answer 9

- At the front of both parietal lobes is the somatosensory area - Sensory information from the skin e.g. touch, heat, pressure, is represented

Answer 10

- In the occipital lobe at the back of the brain is the visual area - Responsible for sight - Damage to the left hemisphere can produce blindness in part of the right visual field of both eyes

Answer 11

- Located in the temporal lobes - Analyses speech-based information - Damage may produce partial hearing loss and damage to a specific area (Wernicke’s area) may affect the ability to comprehend language

Answer 12

* An area of the frontal lobe of the brain in the left hemisphere responsible for speech production. * Identified by Paul Broca- a surgeon- in the 1880s. * Damage to Broca’s area causes Broca’s aphasia which is characterised by speech that is slow, laborious and lacking in fluency. * Does not affect understanding * Difficulty with prepositions and junctions

Answer 13

* An area of the temporal lobe in the left hemisphere, responsible for language comprehension. * Wernicke’s aphasia occurs due to damage to this area and results in fluent, but meaningless language - have no problem producing language, but understanding it * People with Wernicke’s aphasia will often produce nonsense words (neologisms) as part of the content of their speech.

Answer 14

P - One strength is that there is research to support that the brain has localised functions. E - Phineas Gage was working on a railroad and accidentally ignited an explosive causing a metre-length pole to hurl through his left cheek, passing behind his left eye, exiting his skull from the top of his head, taking a portion of his brain with it (most of his left frontal lobe). He survived and the only thing that changed was his personality which became rude and quick-tempered. E - Gage is seen as a landmark case in science as the change in his temperament following the accident suggested that the frontal love may be responsible for regulating mood.

Answer 15

Evidence from brain scans P - Another strength is evidence from brain scans that supports the idea that many everyday brain functions are localised E - For example, Petersen et al (1988) 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. Also, a review of long-term memory studies by Buckner and Petersen (1996) revealed that semantic and episodic memories reside in different parts of the prefrontal cortex. These studies confirm localised areas for everyday behaviours. E - Therefore objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised.

Answer 16

P - One limitation is that language may not be localised just to Broca’s and Wernicke’s areas E - A recent review by Dick and Tremblay (2016) found that only 2% of modern researchers think that language in the brain is completely controlled by Broca’s and Wernicke’s areas. Advances in brain imaging techniques, such as fMRI, mean that neural processes in the brain can be studied with more clarity than ever before. It seems that language function is distributed far more holistically in the brain than was first thought. So-called language streams have been identified across the cortex, including brain regions in the right hemisphere, as well as subcortical regions such as the thalamus. E - This suggests that, rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts localisation theory.

Answer 17

- The idea that the two hemispheres of the brain are functionally different, and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other, as in the example of language (which is localised and lateralised) - The two hemispheres are connected through nerve fibres called the corpus callosum which facilitate inter-hemispheric communication.

Answer 18

- A ‘split-brain’ operation involved severing the connection between the right hemisphere and left hemisphere, mainly the corpus callosum - This is a surgical procedure to reduce epilepsy

Answer 19

Sperry (1968) devised a system to study how two separated hemispheres deal with, for example, speech and vision

Answer 20

11 people who had a split-brain operation were studied - an image could be projected to a participants right visual field (RVF) - processed by the left hemisphere (LH) - and the same or different image could be projected to the left visual field (LVF) - processed by the right hemisphere (RH). In the ‘normal’ brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture of the visual world. However, presenting the image to one hemisphere of a split-brain participant meant that the information cannot be conveyed from that hemisphere to the other.

Answer 21

When a picture of an object was shown to a participant’s RVF (linked to LH), the participant could describe what was seen. But they could not do this if the object was shown to the LVF (RH) - they said there was ‘nothing there’. This is because, in the connected brain, messages from the RH are relayed to the language centres in the LH, but this is not possible in the split brain. Although participants could not give verbal labels to objects projected to the LVF, they could select a matching object out of sight using their left hand (RH), as well as the left hand. If a pinup picture was shown to the LVF there was an emotional reaction (e.g. giggle) but the participants usually reported seeing nothing or just a flash of light.

Answer 22

These observations show how certain functions are lateralised in the brain and support the view that the LH verbal and the Rh is ‘silent’ but emotional

Answer 23

P – one strength of split-brain research into hemispheric lateralisation is that there is a wealth of information and research findings. E – for example findings that the left hemisphere is more analytical that the right hemisphere. E – this is important because it has contributed to our understanding of processes in the brain.

Answer 24

P – Even though there is a lot of evidence from research, this does not mean that it is generalisable beyond the research setting. E – Split brain patients do not have typical brains, as they have undergone a certain amount of trauma through the process of severing the corpus collosum. E – This is a problem because we cannot necessarily generalise the findings to people who have not experienced this operation. Additionally, the findings may only show what happens when the communication channel is no longer intact – it does not show that this is still the case if the corpus collosum is allowing communication between the hemispheres.

Answer 25

P – a major strength of split-brain research is that it uses highly standardised procedures. E – for example, the image projected was flashed up for only one-tenth of a second meaning that the image could only be viewed by one hemisphere. E – this means that the research can be viewed as scientific, which is internally valid as it has controlled extraneous variables.

Answer 26

* Plasticity, also referred to as neuroplasticity or cortical remapping, describes the brain’s tendency to change and adapt (functionally and physically) as a result of experience and new learning. * During infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 at age 2-3 years. * As we age, rarely used connections are deleted and frequently used connections are strengthened- synaptic pruning. * It was originally thought that plasticity occurred in infancy and childhood and the adult brain remains fixed and static. * However, more recent research suggests that at any time in life, existing neural connections can change, or new neural connections can be formed, as a result of learning and experience.

Answer 27

o Studied the brains of London taxi drivers and found significantly more volume or grey matter in the posterior hippocampus than in a matched control group. o This part of the brain is associated with the development of spatial and navigational skills in humans and other animals. As part of their training, London cabbies must take a complex test called ‘The Knowledge’, which assesses their recall of the city streets and possible routes. o Maguire et al. found that this learning experience alters the structure of the taxi driver’s brains. They also found that the longer the taxi drivers had been in the job, the more pronounced was the structural difference (a positive correlation)

Answer 28

by Draganski et al. 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 learning.

Answer 29

P - One limitation of plasticity is that it may have negative behavioural consequences E - Evidence has shown that the brain’s adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increased risk of dementia (Medina et al. 2007). Also, 60-80% of amputees have been known to develop phantom limb syndrome - the continues experience of sensations in the missing limb as if it were still there. These sensations are usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss. E - This suggests that the brain’s ability to adapt to damage is not always beneficial

Answer 30

P - One strength is that brain plasticity may be a life-long ability. E - In general plasticity reduces with age. However, Bezzola et al. (2012) demonstrated how 40 hours of gold training produced changes in the neural representations of movement in participants aged 40-60. Using fMRI, the researchers observed increased motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training. E - This shows that neural plasticity can continue throughout the lifespan.

Answer 31

* Following physical injury, or other forms of trauma, unaffected areas of the brain are often able to adapt and compensate for those areas that are damaged. * The functional recovery that may occur in the brain after trauma is another example of neuroplasticity. * Healthy areas may take over the functions of those areas that are damaged, destroyed or missing. * This can happen very quickly!

Answer 32

P - One strength of functional recovery research is its real-world application. E - understanding the processes involved in plasticity has contributed to the field of neurorehabilitation. Simply understanding that axonal growth is possible encourages new therapies to be tried. For example constraint-induced movement therapy is used with stroke patients whereby they repeatedly practise using the affected part of their body (such as an arm) while the unaffected arm is restrained. E - This shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made.

Answer 33

P - One limitation of functional recovery is that level of education may influence recovery rates. E - Schneider et al. (2014) 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 16 years’ education compared to about 10% of those who had less than 12 years’ education. E - This would imply that people with brain damage who have insufficient DFR are less likely to achieve a full recovery.

Answer 34

o fMRIs work in the same way as standard MRIs but show activity as it occurs (functions). o fMRIs measure the energy released by haemoglobin (the protein content of blood). o When an area of the brain is active, it uses more oxygen, and haemoglobin reacts differently when it has oxygen. o When the brain is scanned, it picks up this change. o The fMRI produces a 3D moving image, which shows which parts of the brain are active during particular mental processes, which is important for our understanding of localisation of function.

Answer 35

o One strength of fMRI is, unlike other scanning techniques, such as PET, it does not rely on the use of radiation. o If administered correctly it is virtually risk-free, non-invasive and straightforward to use. It also produces images that have very high spatial resolution, depicting detail by the millimetre, and providing a clear picture of how brain activity is localised. o fMRI provides a moving picture of brain activity, which means that patterns of activity can be compared rather than just the physiology of the brain. This means that fMRI can safely provide a clear picture of brain activity.

Answer 36

o fMRI machines are expensive to buy and maintain and they require trained operators. o fMRI can only capture a clear image if the person stays perfectly still i o It has poor temporal resolution because there is around a 5-second time0lag behind the image on screen and the initial firing of neuronal activity, meaning fMRI may not truly represent moment-to-moment brain activity. o fMRI measures the blood flow, not the activity of individual neurons, so it can be difficult to tell what kind of brain activity is being picked up.

Answer 37

o Electroencephalograms are records of the tiny electrical impulses produced by the brain’s activity. o Electrodes are placed on the scalp using a skull cap. o By measuring characteristic wave patterns, the EEG can help diagnose certain conditions of the brain such as epilepsy and tumours.

Answer 38

o EEG has been useful in studying the stages of sleep and in the diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of activity in the brain that can easily be detected on screen. o Unlike fMRI, EEG technology has extremely high temporal resolution. o EEG can accurately detect brain activity at a resolution of a single millisecond - showing real-world usefulness of the technique o Cheaper than other techniques

Answer 39

o Expertise is required to interpret the output from EEGs. o The information received from EEGs is generalised, so they are not useful in pinpointing the exact source of neural activity - therefore does not allow researchers to distinguish between activities originating in different but adjacent locations

Answer 40

o Event-related potentials use the same apparatus as EEGs, but record when there is activity in response to a stimulus. o Using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out, leaving only the response to the given stimulus.

Answer 41

o ERPs are cheaper than other scanning techniques. o The limitations of EEGs are addressed through ERPs because they are much more specific. o ERPs are used in the measurement of cognitive functions and deficits. o ERPs have much more temporal resolution (time it happens) than neuroimaging techniques such as fMRI.

Answer 42

o Expertise is required to interpret the output from EEGs. o It can be very difficult to eliminate all background noise and extraneous material, which is necessary for the collection of ERP data.

Answer 43

o Port-mortem examinations involve the brain being analysed after death to determine whether certain observed behaviours during the patient’s lifetime can be linked to abnormalities in the brain.

Answer 44

o There is no discomfort for the individual (as they are dead). o Post-mortems have been an vital part of our early understanding of the brain (before neuroimaging was a possibility). o Post-mortems help generate hypotheses for further study. o Broca and Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility o Post-mortem studies were also used to study HM’s brain to identify the areas of damage, which could then be associated with his memory deficits - showing post-mortems continue to provide useful information

Answer 45

o It is not possible to do a comparison with a brain before death, and some brains may have been affected by the cause of death, being subject to trauma or decay o There is no brain activity, so only the structure of the brain can be studied (no processes). o There may be ethical issues regarding informed consent from the individual, for example in the case of HM who lost his ability to form memories and was not able to provide such consent - nevertheless post-mortem research has been conducted on his brain.

Answer 46

Distinct patterns of changes in body activity that conform to cyclical time periods. All biological rhythms are subject to the body’s internal biological ‘clocks’ and external changes in the environment

Answer 47

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

Answer 48

A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep

Answer 49

A type of biological rhythm, subject to a 24-hour cycle, which regulates a number of body processes such as the sleep/wake cycle and changes in core body temperature

Answer 50

Internal body clock that regulate many of our biological mechanisms

Answer 51

External cues that may affect our biological rhythms

Answer 52

o Our fairly consistent sleep pattern suggests an internal or endogenous mechanism - the biological clock o However, this can be overridden by psychological factors, such as anxiety or by exogenous zeitgebers

Answer 53

PROCEDURES o Michael Siffre is a self-styled caveman who has spent several extended periods underground to study the effects of his own biological rhythms o Deprived of exposure to natural light and sound, but with access to adequate food and drink - Siffre resurfaced in mid-September 1962 after two months in the caved of the Southern Alps believing it to be mid-August o A decade later he performed a similar feat but this time for six months in a Texan cave FINDINGS o In each case, his ‘free-running’ biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours) though he did continue to fall asleep and wake up on a regular schedule

Answer 54

PROCEDURES o Similar results were recorded by Aschoff and Wever (1976) who convinced a group of participants to spend four weeks in a World War 2 bunkers deprived of natural light FINDINGS o All but one of the participants (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24 and 25 hours CONCLUSIONS o Both Siffre’s experience and the bunker study suggest that the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but that it is entrained by exogenous zeitgebers associated with our 24-hour day (such as the number of daylight hours, typical mealtimes, etc.)

Answer 55

PROCEDURES o Folkard et al studied a group of 12 people who agreed to live in a dark cave for three weeks, retiring to bed when the clock said 11:45pm and rising when it said 7:45am o Over the course of the study, the researchers gradually sped up the clock (unbeknownst to the participants) so an apparent 24-hour day eventually only lasted 22 hours FINDINGS o It was revealed that only one of the participants was able to comfortably adjust to the new regime CONCLUSIONS o This would suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by exogenous zeitgebers

Answer 56

P - One strength of research into circadian rhythms is that it provides an understanding of the adverse consequences that occur when they are disrupted. E - For example, night workers engaged in shift work experience a period of reduced concertation around 6 in the morning (a circadian trough) meaning mistakes and accidents are more likely. Research has also pointed to a relationship between shift work and poor health - shift workers are three times more likely to develop heart disease than people who work more typical work patterns. E - This shows that research into the sleep/wake cycle may have real-world economic implications in terms of how best to manage worker productivity.

Answer 57

P - However, studies investigating the effects of shift work tend to use correlational methods. This means it is difficult to establish whether desynchronisation of the sleep/wake cycle is actually a cause of negative effects as there may be other factors. E - For example, 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 family events. E - This suggests that it may not be biological factors that create the adverse consequences associated with shift work.

Answer 58

P - Another strength of research into circadian rhythms is that it has been used to improve medical treatments. E - Circadian rhythms co-ordinate a number of the body’s basic processes such as heart rate, digestion and hormone levels. This 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 person’s biological rhythms. For example, aspirin as a treatment for heart attacks is most effective if taken last thing at night. Aspirin reduces blood platelet activity, and this can reduce the risk of heart attack. Heart attacks are most likely to occur early in the morning, so the timing of taking aspirin matters - research has supported this. E - This shows that circadian rhythm research can help increase the effectiveness of drug treatments.

Answer 59

P - One limitation of research into circadian rhythms is that generalisations are difficult to make E - The studies of Aschoff and Wever and Siffre are based on very small samples of participants - for example Siffre only used himself as a case study. Research has found individual differences in sleep/wake cycles can vary from 13 to 65 hours. In addition, Duffy et al found that some people naturally prefer to go to bed early and wake up early and vice versa. Even Siffre found in a later study that his sleep/wake cycle has slowed down since he was a young man. E - This means that it is difficult to use the research data to discuss anything more than averages, which may be meaningless.

Answer 60

* The female menstrual cycle is an example of an infradian rhythm, governed by monthly changes in hormone levels which regulate ovulation. * The cycle refers to the time between the first day of a woman’s period, to the day before her next period. * The typical cycle takes 28 Days to complete (between 24 and 35 is considered normal). * Rising levels of the hormone oestrogen cause the ovary to develop and release an egg (ovulation). * After this, the hormone progesterone helps the womb lining to thicken making the body ready for pregnancy. * If pregnancy does not occur, the egg is absorbed into the body, the womb lining comes away and leaves the body (menstrual flow).

Answer 61

* Seasonal affective disorder (SAD) is a depressive disorder which has a seasonal pattern of onset, and is described and diagnosed as a mental disorder in DSM-5 * Symptoms - low mood, general lack of activity and interest in life * Often referred to as the winter blues - symptoms usually triggered in winter months when the number of daylight hours becomes shorter * It is a type of infradian rhythm known as a circannual rhythm as it is subject to a yearly cycle * Also be classed as a circadian rhythm as the experience of SAD may be due to the disruption of the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter * It is hypothesised that the cause of SAD lies in the production of melatonin, because the extra melatonin secreted in winter months (because of the shorter days and longer nights) has an effect on the production of serotonin. Serotonin production is linked to depression.

Answer 62

P - There is research to suggest that the menstrual cycle is to some extent governed by exogenous zeitgebers E - Reinberg (1967) examined a woman who spent three months in a cave with only a small lamp to provide light. Reinberg noted that her menstrual cycle shortened from the usual 28 days to 25.7 days. E - This result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors on infradian rhythms

Answer 63

P - There is further evidence to suggest that exogenous zeitgebers can affect infradian rhythms. E - Russell et al. (1980) found that female menstrual cycles became synchronised with other females through odour exposure. In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised. E - This suggests that the synchronisation of menstrual cycles can be affected by pheromones, which have an effect on people nearby rather than on the person producing them.

Answer 64

P - One limitation of synchronisation studies is their methodological shortcomings. E - There are many factors that may effect change to the menstrual cycle, including stress, changes in diet, exercise, etc. 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. This may explain why other studies have failed to replicate the findings. E - This suggests that menstrual synchrony studies are flawed.

Answer 65

P - one of the most effective treatments for SAD is light therapy, a box which stimulates very strong light to reset the body’s internal clock. E - studies shows this helps reduce the effects of SAD in about 80% of people. Light therapy is also preferred over antidepressants to treat SAD as it is regarded as safe. COUNTER That said, light therapy can produce headaches and eye strain. Perhaps more tellingly, Kelly Rohan et al. (2009) recorded a relapse rate of 46% over successive winters, compared to 27% in a comparison group receiving CBT.

Answer 66

* Sleep is viewed as necessary for physiological recovery; to restore the body and brain after the day’s exertions.

Answer 67

* Horne (1988) believes that sleep is mainly a function both by and for the brain, which is brain restoration. He terms stage 4 of SWS and REM sleep as core sleep. Core sleep is essential for normal brain functioning since this is when the brain recovers and restores itself. Other stages of sleep are viewed as more adaptable and not so essential (‘optional sleep’).

Answer 68

* Oswald’s (1980) restoration model proposes that the high level of brain activity during REM reflects recovery of the brain, while the increase in hormone activity during SWS reflects restoration and recovery in the body.

Answer 69

Psychologists have identified 5 distinct stages of sleep that altogether span approximately 90 minutes - a cycle that occurs throughout the course of the night. Each of these stages is characterised by a different level of brainwave activity which can be monitored using an EEG

Answer 70

Light sleep, person can be easily woken. Brainwave patterns become slower and more rhythmic (alpha waves), and become even slower as sleep becomes deeper (theta waves).

Answer 71

Involves delta waves (which are even slower than theta), they have a greater amplitude than earlier wave patterns. This is known as ‘deep sleep’ or ‘slow wave sleep’ and it is hard to wake a person at this point.

Answer 72

At this point the body is paralysed and brain activity speeds up in a way that resembles the awake brain. REM occurs at this point. Research suggests that REM is associated with dreaming.

Answer 73

P - The case study indicates the flexibility of ultradian rhythms E - Randy Gardener remained awake for 264 hours. While he experienced numerous problems such as blurred vision and disorganised speech, he coped rather well with the massive sleep loss. After this experience, Randy slept for just 15 hours and over several nights he recovered only 25% of his lost sleep. Interestingly, he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the other stages. E - These results highlight the large degree of flexibility in terms of the different stages within the sleep cycle and the variable nature of this ultradian rhythm.

Answer 74

P - The problem with studying sleep cycles is the differences observed in people, which make investigating patterns difficult. E - Tucker et al. (2007) found significant differences between participants in terms of the duration of each stage, particularly stages 3 and 4 (just before REM sleep). E - This demonstrates that there may be innate individual differences in ultradian rhythms, which means that it is worth focusing on these differences during investigations into sleep cycles.

Answer 75

P - One strength of research into ultradian rhythms is that it has improved understanding of age-related changes in sleep. E - Sleep scientists have observed that SWS reduces with age. Growth hormone is mostly produced during SWS; therefore, this is reduced in older people. according to Van Cauter et al. (2000), the resulting sleep deficit may explain various issues in old age, such as reduced alertness. In order to increase SWS, relaxation and medication may be used. E - This suggests that knowledge of ultradian rhythms has practical value

Answer 76

In mammals, the main endogenous pacemaker is a tiny cluster of nerve cells called the suprachiasmatic nucleus (SCN), which lies in the hypothalamus in each hemisphere of the brain.

Answer 77

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 (supra) the optic chiasm.

Answer 78

The SCN plays an important role in generating the body’s circadian rhythm. It acts as the ‘master clock’, with links to other brain regions that control sleep and arousal, and has control over other biological clocks throughout the body. Neurons within the SCN spontaneously synchronise with each other, so that their target neurons in sites elsewhere in the body receive correctly time-coordinated signals.

Answer 79

The SCN needs resetting only when external light levels change. It receives information about light levels via the optic nerve. This even happens when our eyes are shut, because light penetrate the eyelids e.g. if the sun rises earlier than on the previous day, the morning light automatically adjusts the clock.

Answer 80

The SCN also regulates the manufacture and secretion of melatonin in the pineal gland.

Answer 81

* Bred a strain of hamsters so that they had abnormal circadian rhythms of 20 hours rather than 24 hours. * SCN neurons from these abnormal hamsters were then transplanted into the brains of normal hamsters. * These normal hamsters then displayed the same abnormal circadian rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern onto the recipient’s brains.

Answer 82

* 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 (they were awake and vulnerable when they should have been asleep).

Answer 83

The pineal gland is a pea like structure just behind the hypothalamus. The SCN sends signals to the pineal gland directing it to increase production and secretion of the hormone melatonin at night and to decrease it as light levels increase in the morning. Melatonin induces sleep by inhibiting the brain mechanisms that promote wakefulness.

Answer 84

* Receptors in the SCN are sensitive to changes in light levels during the day and use this information to synchronise the activity of the body’s organs and glands. * Light resets the internal biological clock each day, keeping it to a 24-hour cycle. * Rods and cones in the retina of the eye select light to form visual images. * A third type of light-detecting cell in the retina gauges overall brightness to set the internal biological clock. * A protein called melanopsin is critical in this. A small number of retinal cells contain melanopsin and carry signals to the SCN to set the daily cycle.

Answer 85

* Demonstrated that light may be detected by skin receptor sites on the body even when the same information is not received by the eyes. * 15 participants were woken at various times and a light pad was shone on the back of their knees. * The researchers managed to produce a deviation in the participants usual sleep/wake cycle of up to 3 hours in some case. * This suggests that light is a powerful exogenous zeitgeber that need not necessarily rely on the eyes to exert its influence on the brain.

Answer 86

Found that exposure to bright light prior to an east-west flight decreased the time needed to readjust to local time on arrival. Volunteers participated in one of three treatments 1) Continuous bright light 2) Intermittent bright light 3) Dim light each of which shifted their sleep-wake cycle back by one hour a day over 3 days. Participants exposed to continuous bright light shifted their circadian rhythm by 2.1 hours over the course of the study, compared with 1.5 hours for intermittent bright light and 0.6 hours for dim light. As a result, participants in the first group felt sleepier 2 hours earlier in the evening and woke 2 hours earlier in the morning which was closer to the local time conditions after the east-west flight.

Answer 87

* Social stimuli such as mealtimes and social activities may also have a role as zeitgebers. * Aschoff et al (1971) showed that individuals are able to compensate for the absence of zeitgebers such as natural light by responding to social zeitgebers instead

Answer 88

Found that the circadian rhythms of air travellers adjusted more quickly if they went outside more at their destination. This was thought to be because they were exposed to the social cues of their new time zone, which acted as a zeitgeber.