Biopsychology - P2 Flashcards

Question

What are the terminal buttons of a neuron? - AO1

Answer 1

Terminal buttons at the end of the Axon communicate with the next neuron in the chain across a gap called the synapse.

Answer 2

- 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, the inside of the cell becomes positively charged for a split second, causing an action potential to occur. - This creates an electrical impulse that travels down the Axon towards the end of the neuron.

Answer 3

Each neuron is separated from the next by an extremely tiny gap, called the synapse.

Answer 4

Signals within neurons are transmitted electrically, but signals between neurons are transmitted chemically across the synapse.

Answer 5

1) When the electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggers the release of neurotransmitter from the tiny sacs called synaptic vesicles. 2) Once a neurotransmitter crosses the gap, it is taken up by a postsynaptic receptor site on the next neuron, so the impulse only ever travels in one direction. 3) The chemical message is converted back into an electrical impulse and the process of electrical transmission begins.

Answer 6

Neurotransmitters are chemicals that diffuse across the synapse to the next neuron in the chain.

Answer 7

Many neurotransmitters have been identified. Each has its own specific molecular structure that fits perfectly into a postsynaptic receptor site, like a lock and key. Each has specific functions. For example: - Acetylcholine (ACh) found where a motor neuron meets a muscle, causing muscles to contract - Serotonin affects mood and social behaviour, among other things, which is why it is being implicated as a cause of depression.

Answer 8

Excitatory and inhibitory influences are summed and must reach a certain threshold in order for the action potential of the postsynaptic neuron to be triggered. If the net effect of the neurotransmitters is inhibitory, then the postsynaptic neuron is less likely to fire (i.e., no electrical signal is transmitted). It is more likely to fire if the net effect is excitatory.

Answer 9

Adrenaline = Generally excitatory Serotonin = Really inhibitory Dopamine = Equally both

Answer 10

The excitatory and inhibitory influences on the post-synaptic neuron are summed (added together), if the net effect on the post-synaptic is inhibitory, the neuron will be less likely to ‘fire’ and if the net effect is excitatory, the neuron will be more likely to ‘fire.’

Answer 11

The theory that different areas of the brain are responsible for specific behaviours, processes or activities - theory argued + created by Broca and Wernicke

Answer 12

the theory that all parts of the brain were involved in the processing of thought and action - believed by scientists before Broca + Wernicke's research and before Phineas Gage research

Answer 13

Part of the brain, the cerebrum, is divided into two symmetrical halves called the right and left hemisphere. Some of our physical and psychological functions are controlled or dominated by a particular hemisphere. This is called lateralisation.

Answer 14

As a general rule, activity on the left hand side of the body is controlled by the right hemisphere, and activity on the right hand side of the body by the left. Language is linked to the left hemisphere.

Answer 15

- The cerebral cortex, or cortex, is the outer layer of both hemispheres. - The cortex of both hemispheres is subdivided into four centres called the lobes of the brain: the frontal lobe, the parietal lobe, the occipital lobe and the temporal lobe.

Answer 16

A lobe is a part of an organ that is separate in some way from the rest. Each lobe in the brain is associated with different functions.

Answer 17

- At the back of the frontal lobe in both hemispheres is the motor area, which 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 18

- At the front of both parietal lobes is the somatosensory area, which is separated from the motor area by a valley called the Central Sulcus. - The somatosensory area is where sensory information from the skin, e.g. related to touch, heat, pressure, etc. Is represented. - The amount of somatosensory area devoted to a particular body part donates its sensitivity. For instance, receptors for our face and hands occupy over half of the somatosensory area.

Answer 19

- In the occipital lobe, at the back of the brain is the visual area, or visual cortex. 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. - This means that damage to the left hemisphere, for example, can produce blindness in part of the right visual field of both eyes.

Answer 20

- The temporal lobes house the auditory area which analyses speech based information. - Damage may produce partial hearing loss. The more extensive the damage, the more extensive the loss.

Answer 21

- Is an area of the frontal lobe in the left hemisphere (in most people) responsible for speech production. - Damage to Broca's area causes broca's aphasia, which is characterised by a speech that is slow, laborious, and lacking in fluency.

Answer 22

- Broca carried out a post mortem on the brain of a patient known as ‘Tan’ - This patient was only able to say ‘Tan’ - Broca found that he had part of his left frontal lobe missing, leading to a language function being associated with this area of the brain.

Answer 23

- Is an area of the temporal lobe (encirculating the auditory cortex) in the left hemisphere (in most people) responsible for language comprehension. - Damage to Wernicke’s area will result in Wernicke's aphasia, often producing nonsense words, neologism as part of content of their speech.

Answer 24

One strength is that damage to areas of the brain have been linked to mental disorders. - Neurosurgery is a last resort method for treating some mental disorders, targeting specific areas of the brain which may be involved. - Darin Dougherty et. al (2002) reported on 44 people with OCD who had undergone a cingulotomy. A post-surgical follow up after 32 weeks, about 30% had met the criteria for successful response to the surgery and 14% for partial response. - The success of these procedures suggest that behaviours associated with serious mental disorders may be localised.

Answer 25

Another strength is evidenced from brain scans that support the idea that many everyday brain functions are localised. - For instance, Stephen Peterson 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. - A study for long-term memory by Endel Tulving et. al (1944), revealed that semantic and episodic memories reside in different parts of the prefrontal cortex. - These studies confirm localised areas for everyday behaviours. Therefore, objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised.

Answer 26

- A challenge to localisation theory comes from the work of Karl Lashley (1950). Lashley removed areas of the cortex between 10% and 50% in rats that were learning the route through a maze. No area was proven to be more important than any other area in terms of the rats’ ability to learn the route. - The process of learning seemed to require every part of the cortex, rather than being confined to a particular area. Suggests that higher cognitive processes such as learning or not localised but distributed in a more holistic way in the brain.

Answer 27

A limitation is that language may not be localised just to Broca’s and Wernicke’s areas. - A recent review by Anthony Dick and Pascal 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 and including brain regions in the right hemisphere as well as subcortical regions such as the thalamus. - This suggests rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts localisation theory.

Answer 28

The idea that the two hemispheres of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by 1 hemisphere rather than the other as in the example of language.

Answer 29

A series of studies which began in the 1960s forward, involving people with epilepsy who had experienced a surgical separation of the hemispheres of the brain to reduce the severity of their epilepsy. This enabled researchers to test lateral functions of the brain in isolation.

Answer 30

- Localisation refers to the fact that some functions, e.g., vision and language are governed by very specific areas in the brain. - Lateralisation refers to the fact that there are two sides called hemispheres of the brain and some functions appear in both hemispheres.

Answer 31

- Known as the analyser. - Controls the right side of the body. - Viewed objects are visible in the right visual field. - The finer image details are seen Has two main centres, Broca's area which is the frontal lobe and Wernicke's area which is in the temporal lobe, therefore showing the brain is lateralized. - understanding of language.

Answer 32

- Known as the synthesiser. - Controls the left side of the body. - Viewed objects are visible in the left visual field. - Used for drawing due to motor area. - The wider visual picture. - Emotional context of language.

Answer 33

- Sperry’s participants had undergone the splitting of the corpus callosum. - Sperry devised a general procedure in which an image or word could be projected to a patient's right visual field, which is processed by the left hemisphere, and the same or different image could be projected to the left visual field, which is 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 word. - However, presenting the image to one hemisphere of a split-brain patient meant that the information could not be conveyed from that hemisphere to the other.

Answer 34

Strength is research showing that even in normal brains, the two hemispheres process information differently. - Fink et al. (1996) used PET scans to investigate visual processing. - They found that different sides were more active. - This suggests that, at least as far as visual processing is concerned, hemispheric lateralisation is a feature of the normal brain as well as the split-brain.

Answer 35

One limitation is the idea that the LH as analyzer and RH as synthesiser may be wrong. - There may be different functions in the RH and LH, but research suggests people do not have a dominant side of their brain, which creates a different personality. - Nielsen et al. (1996) found that people used certain hemispheres for different tasks, but there was no evidence of a dominant side. - This suggests that the notion of right-or-left-brained people is wrong.

Answer 36

There is research to support Sperry's conclusions from more recent split-brain research. - Gazzaniga (Luck et.al. 1989) showed split brain participants actually performed better than normal control groups on certain tasks. - For example, they were faster at identifying odd ones out in an array of similar objects than controls.

Answer 37

Sperry used a lot of controls in his research. - For example, the image only flashed on the screen for a 10th of a second. - This meant that they can't look to the other side of the screen. - This increases the validity of the study as it acts as a control making it more scientific.

Answer 38

There are generalisation issues with Sperry’s study. - casual relationships are hard to establish. The behaviour of split-brain participants was compared to a neurotypical control group. - The issue was that none of the participants in the control group had epilepsy, which is a major confounding variable. - Any differences observed between two groups may be a result of epilepsy then split-brain.

Answer 39

This describes the brain's tendency to change and adapt as a result of experience on new learning. Generally involves the growth of new connections.

Answer 40

During infancy, the brain experiences rapid growth in the number of synaptic connections, peaking around 15000 at two to three years old (Gopnik et al. 1999) double the amount of an adult.

Answer 41

- As we age, rarely-used connections are deleted and frequently-used connections are strengthened, also known as synaptic pruning. - People once thought the adult brain wasn't capable of change, but now understand synaptic pruning enables lifelong plasticity, where new neural connections are formed in response to new demands on the brain.

Answer 42

Maguire et al. (2000) studied London taxi driver brains. He found significantly more volume of grey matter in the posterior hippocampus than in a matched control group.

Answer 43

The hippocampus is associated with development of spatial and navigational skills in humans and animals.

Answer 44

As part of training, taxi drivers have to take ‘The knowledge’ test.

Answer 45

Draganski et al. (2006) imaged brains of medical students three months before and after final exams. Learning-induced changes were seen to have occurred in the posterior hippocampus, and parietal cortex, presumably as a result of learning.

Answer 46

It is a form of plasticity. Following damage through trauma, the brain's ability to redistribute or transfer functions, usually performed by a damaged area(s), to other undamaged areas.

Answer 47

- Unaffected areas of the brain are often able to adapt and compensate for those areas that are damaged. - Healthy brain areas may take over the functions of the damaged. - This is spontaneous recovery that then shows after weeks/months.

Answer 48

- Axonal sprouting. - Denervation Supersensitivity. - Recruitment of homologous areas on the opposite side of the brain.

Answer 49

The growth of new nerve endings, which connect with other undamaged nerve cells to form new neural pathways.

Answer 50

Occurs when axons that do a similar job become aroused to a higher level to compensate for ones lost.

Answer 51

This means specific tasks can still be performed. e.g. Broca’s area is damaged on the left, the right equivalent will carry out its function. It may then shift back to the left side.

Answer 52

One strength of plasticity is that it does not always decline sharply with age. - Plasticity reduces with age. However, Bezzola et al. (2012) demonstrated how 40 hours of golf training produced changes in the neural representation of movement in participants aged 40 to 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. - This shows that neural plasticity can continue throughout the lifespan.

Answer 53

Limitation of plasticity is that 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, as well as an increased risk of dementia. Medina et al. (2007). - Also, 60 to 80% of amputees have been known to develop phantom limb syndrome, the continued experience of sensations in the missing limb as if it was still there. They're usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss. - This suggests that the brain's ability to adapt to change is not always beneficial.

Answer 54

One strength of Functional Recovery Research is its real world application. - 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, e.g. arm, while the unaffected arm is restrained. - Shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made.

Answer 55

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

Answer 56

- fMRI - EEG - ERPs - Post-mortem examinations

Answer 57

- Detects changes in both blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain, producing 3D images. - If an area is more active, it means that it has consumed more oxygen and to meet this need blood flow is directed to the active area, the haemodynamic response.

Answer 58

- It does not rely on the use of radiation. - It is virtually risk-free, non-invasive and straightforward to use. - produces images with very high spatial resolution and provides clear pictures of how brain activity is localised.

Answer 59

- It is expensive compared to other neuroimaging techniques. - Has poor temporal resolution because there's around a 5 second time lag behind imaging on stream and initial firing of neurological activity.

Answer 60

- Measures electrical activity within the brain via electrodes fixed to scalp using a skull cap. - Scan recording represents the brainwave patterns generated from the action of thousands of neurons. EEG is often used by clinicians as a diagnostic tool, as unusual arhythmic patterns of activity may indicate neurological abnormalities.

Answer 61

- Useful in studying stages of sleep and diagnosis of conditions such as epilepsy. - Has extremely high temporal resolution, which is what's happening at the time of scanning. - Today, it can detect brain activity at a resolution of a single millisecond.

Answer 62

- Main drawback is the generalised nature of info received. - EEG signal isn't useful for pinpointing the exact source of neural activity, therefore doesn't allow researchers to distinguish activities originating in different but adjacent locations.

Answer 63

- Researchers developed a way of teasing out and isolating all neural responses associated with specific motor, sensory and cognitive events. - Using statistical averaging technique, all extraneous brain activity from original EEG is filtered out learning event-related potential ERPs - Types of brain waves triggered by particular events.

Answer 64

- Bring more specificity into measurement of neural processes. - Have excellent temporal resolution. - ERPs are more used to measure cognitive functions and deficits.

Answer 65

- Critics have pointed out a lack of standardisation in ERP methodology between different research studies which makes it difficult to confirm findings. - In order to establish pure data background noise and extraneous material must be completely eliminated.

Answer 66

- Involves analysis of a person's brain after death. - Those subject to this examination are likely with a rare disorder or experienced unusual deficits in mental processes or behaviour during life.

Answer 67

- Post-mortem evidence was vital for the foundation for early understanding of key processes. - Broca and Wernicke relied on post-mortem studies in establishing the link between language, brain and behaviour - Used to study areas of damage.

Answer 68

- Causation is an issue. Observed damage to the brain may not be linked to deficits under review, but to some other unrelated trauma/decay. - Post mortem studies raise ethical issues of consent from the person before death as they may not have informed consent, challenges usefulness.

Answer 69

Distinct patterns of changes in body activity that conform to cyclical time periods - Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers)

Answer 70

Biological rhythms subject to a 24-hour cycle, which regulate a number of body processes such as the sleep/wake cycle and changes in core body temperature

Answer 71

Circadian rhythms co-ordinate a number of the body's basic processes such as heart rate, digestion and hormone levels - these rise and fall during the course of the day which is led to the field of chronotherapeutics

Answer 72

- Some of these biological rhythms occur many times during the day (ultradian rhythms) - Others take longer than a day to complete (infradian rhythms) - And in some cases much longer (circannual rhythms)

Answer 73

Those rhythms that last for around 24hours - Two examples of circadian rhythms are the sleep/wake cycle and core body temperature

Answer 74

As we feel tired during night-time and alert during the day, it shows the effect of daylight (an important exogenous zeitgeber) on our sleep/wake cycle

Answer 75

The sleep/wake cycle is also governed by an internal (endogenous) pacemaker - a biological ‘clock’ called the suprachiasmatic nucleus (SCN) - the SCN provides info from eye about light

Answer 76

He is a self-styled caveman who spent several extended periods underground to study the effects of his own biological rhythms

Answer 77

Deprived of exposure to natural light and sound, but access to adequate food and drink, Siffre resurfaced after spending 2 months in a cave

Answer 78

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 on a regular schedule

Answer 79

Similar results were recorded by Ashoff and Wever in 1976, who convinced a group of participants to spend 4 weeks in a World War 2 bunker deprived of natural light.

Answer 80

All but one of the participants whose sleep/wake cycle extended to 29 hours displayed a circadian rhythm between 24 and 25 hours.

Answer 81

Both Siffre's experience and the bunker study suggests that the 'natural' hours of the 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 meal times, etc.)

Answer 82

- However, we should not overestimate the influence of exogenous zeitgebers on our internal biological clock Folkard et al. (1985) studied a group of 12 people who agreed to live in a dark cave for three weeks, retiring to bed when the clock said 11:45 PM and rising when it said 7:45 AM. - Over the course of the study, the researchers gradually speeded up the clock unbeknown to the participants, so an apparent 24 hour day eventually lasted only 22 hours.

Answer 83

It was revealed that only one of the participants was able to comfortably adjust to the new regime. This would suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by exogenous zeitgebers.

Answer 84

Strength is that it provides an understanding of the adverse consequences that occur when they are disrupted - desynchronisation. - for example, night shift workers experience a period of reduced concentration around 6 in the morning (a circadian trough) meaning mistakes are more likely (Bovin et al. 1996) - research also pointed to a relationship between shift work and poor health - workers are 3 times more likely to develop heart disease (Knutsson 2003) - shows research into sleep/wake cycle may have real-world economic implications in terms of how best to manage worker productivity

Answer 85

- studies investigating effects of shift work tend to use correlational methods. this means it’s difficult to establish whether desynchronisation of the sleep/wake cycle is actually a cause of negative effects, there may be other effects - E.g. Solomon (1993) concluded high divorce rates in shift workers may be due to strain of deprived sleep and other influences like missing out on important family events. - suggests it may not be biological factors that create adverse consequences associated with shift work

Answer 86

Another strength is that it has been used to improve medical treatments. - chronotherapeutics is 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, as heart attacks are more likely to happen early morning, so timing matters (Bonten et al. 2015). Aspirin reduced blood platelet activity and this can reduce the risk of heart attack - shows that circadian rhythm research can help increase effectiveness of drug treatments

Answer 87

One limitation is that generalisations are difficult to make. - Aschoff and Wever, and Siffre studies are based on very small samples of participants (Siffre is just 1). It seems that sleep/wake cycles may vary widely from person to person - Czeisler et al. (1999) found individual differences in sleep/wake cycle varying from 13-65 hours - Duffy et al. (2001) found some people have a natural preference for going to bed early and rising early (‘larks’) and others are opposites (‘owls’) - Siffre, in a later 1999 study observed that his own sleep/wake cycle had slowed down since he was a young man - means it’s hard to use research data to discuss anything more than averages, which may be meaningless

Answer 88

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

Answer 89

- The female menstrual cycle, an example of an infradian rhythm, is governed by monthly changes in hormone levels which regulate ovulation. - The typical cycle takes approximately 28 days to complete, though anywhere between 24 and 35 days is generally considered normal.

Answer 90

- During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it during ovulation. - After the hormone progesterone helps the womb lining to grow thicker, readying the womb for pregnancy. If no pregnancy, the cycle repeats.

Answer 91

- Although the menstrual cycle is an endogenous system, evidence suggested it may be influenced by exogenous factors such as the cycles of other women. - Stern and McClintock (1998) demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones.

Answer 92

- Stern and McClintock studied 29 women with a history of irregular periods. The pheromones were gathered from 9 of the women at different stages of their menstrual cycles via a cotton pad placed in their armpit. - The pads were worn for at least 8 hours to ensure that pheromones were picked up. They were then treated with alcohol and frozen to be rubbed on the upper lip of the other participants. - On pads from the start of the menstrual cycle were applied to all 20 women on day two. They were all given a pad from the second day of the cycle, and so on.

Answer 93

Stern and McClintock found that 68% of women experience stages to their cycle which brought them closer to the cycle of their ‘odour donor’.

Answer 94

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. It has similar, if not the same type of symptoms as normal depression.

Answer 95

SAD is a particular type of infradian rhythm called a circannual rhythm, as it is subject to a yearly cycle. However, it can 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.

Answer 96

- Psychologists have hypothesised that the 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, the lack of light in the morning means the secretion process continues for longer. - This is thought to have a knock on effect on the production of serotonin in the brain; a chemical that is linked to the onset of depressive symptoms.

Answer 97

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

Answer 98

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

Answer 99

This is light sleep, every person may be easily awoken. - In stage one, the brain waves a high frequency and has a short amplitude. These are alpha waves. - In stage two, the alpha waves continue, but there are occasional random changes in pattern called sleep spindles.

Answer 100

- This is known as deep sleep or slow wave sleep (SWS). - The brain waves are delta waves with lower frequency and higher amplitude. - It is difficult to wake someone at this point.

Answer 101

- The body is paralysed, yet brain activity closely resembles that of the awake brain. - During this time the brain produces theta waves and the eyes occasionally move around, thus rapid eye movement (REM). - Dreams are most often experienced during REM sleep, but may also occur in deep sleep.

Answer 102

One strength of menstrual synchrony research is that it may be explained by natural selection. - Synchronisation of the female metro cycle is thought by some to have evolutionary value. For our distant ancestors, it may have been advantageous for females to menstruate together and become pregnant at the same time. - In a social group, this would allow babies who had lost their mothers during or after childbirth to have access to breast milk, thereby improving their chances of survival. - This suggests that synchronisation is an adaptive strategy.

Answer 103

One limitation of synchronisation studies is their methodological shortcomings. - There are many factors that may affect change in a woman's 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 (Trevathan et al.1993) have failed to replicate the findings. - This suggests that mental synchrony studies are flawed.

Answer 104

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

Answer 105

One limitation of ultradian rhythms researches there is significant variation between people. - Tucker et al. (2007) found large differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4. - Tucker et al. suggests that these differences were likely to be biologically determined. - This makes it difficult to describe ‘normal sleep’ in any meaningful way.

Answer 106

- The endogenous pacemaker - The exogenous zeitgeber

Answer 107

Internal body clocks that regulate many of our biological rhythms, such as the influence of the Suprachiasmatic nucleus (SCN) on the sleep/wake cycle.

Answer 108

External factors that affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle.

Answer 109

It is a tiny bundle of nerves located in the hypothalamus in each hemisphere of the brain. It is one of the primary endogenous pacemakers in the mammalian species and is influential in maintaining circadian rhythms such as the sleep/wake cycle.

Answer 110

- Nerve fibres connected to the eye crossing 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 chiasm. It receives information about light directly from this structure. This continues even when our eyes are closed, enabling the biological clock to adjust to changing patterns of daylight whilst we are asleep.

Answer 111

Decoursey et al. (2000) destroyed the SCN connections in the brain of 30 chipmunks who were then returned to their natural habitat 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.

Answer 112

Ralph et al. (1990) bred ‘mutant’ hamsters with a 20 hour sleep/wake cycle. When SCN cells from the foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cycles of the second group defaulted to 20 hours.

Answer 113

- The SCN passes the information 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 also been suggested as a causal factor in seasonal affective disorder.

Answer 114

- In the absence of external cues, the free-running biological clock that contains the sleep/wake cycle continues to ‘tick’ in a distinct cyclical pattern. - This free-running cycle is then ‘brought into line’ (i.e. entrained) by environmental cues, so there is an interaction of internal and external factors.

Answer 115

- Light - Social cues

Answer 116

- Light can reset the body's main endogenous pacemaker, the SCN, and thus plays a role in the maintenance of the sleep/wake cycle. - Light also has an indirect influence on key processes in the body that control such functions as hormone secretion and blood circulation.

Answer 117

Campbell and Murphy 1998 demonstrated that light may be detected by skin receptor sites on the body even when the same information is not received by the eyes.

Answer 118

- 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 three hours in some cases. - 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 119

At about six weeks of age, the circadian rhythms begin and by about 16 weeks babies' rhythms have been and trained by the schedules imposed by parents, including adults-determined mealtimes and bedtimes.

Answer 120

Research on jet lag suggests that adapting to local times for eating and sleeping (rather than responding to one's own feelings of hunger and fatigue) is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances.

Answer 121

One limitation of SCN research is that it may obscure other body clocks. - Research has revealed that there are numerous circadian rhythms in many organs and cells in the body. The peripheral oscillators are found in the organs, including the lungs, pancreas and skin. They are influenced by the actions of the SCN but also act independently. - Damilola et al. (2000) demonstrated how changing feeding patterns of mice could alter the circadian rhythms of cells in the liver by up to 12 hours, whilst leaving the rhythm of the SCN unaffected. - This suggests other complex influences on the sleep/wake cycle.

Answer 122

Another limitation is that 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 biological 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 the purpose of research. - This suggests the more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of the research.

Answer 123

One limitation is that exogenous zeitgebers do not have the same effect in all environments. - The experience of people who live in places where there is very little darkness in summer and very little light in winter sell a different story from the usual narrative. - For example, the Inuits of the Arctic Circle are said to have similar sleep patterns all year round, despite spending around six months in almost total darkness. - This suggests the sleep/wake cycle is primarily controlled by endogenous pacemakers that can override the environmental changes in light.

Answer 124

Another limitation is evidence that challenges the role of exogenous zeitgebers. - Miles et al. (1977) recount the study of a young man, blind from birth, who had an abnormal circadian rhythm of 24.9 hours. - Exposure to social cues such as regular mealtimes, his sleep/wake cycle could not be adjusted. - This suggests that social cues alone are not effective in resetting the biological rhythm.

Biopsychology - P2 Flashcards

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