biopsychology Flashcards
(101 cards)
1
Q
6 marker- with application
how did (X) through sensory, relay, motor neurons?
A
travels from sensory neurons to the brain, and through this information the impact would be felt. This is carried from PNS to central nervous system in the brain. Information is passed through relay neurons through the brain with the decision making of how to respond to the stimulus. (currently still mostly in CNS. this information is then varied from CNS to effectors (muscle in this case) by motor neurons and the reaction/ reflex is presented
2
Q
what are circadian rhythms?
A
biological rhythms subject to a 24 hour cycle which regulate a number of body processes such as sleep-wake cycles and changes in core temperature
3
Q
what are infradian rhythms?
A
cycle of- more than 24 hours e.g. monthly, seasonally e.g. menstrual cycle, hybernation
4
Q
what are ultradian cycles?
A
multiple times in 24 hours: blood circulation, sleep cycle (90 mins), blinking, respiration
5
Q
what are exogenous zeitgebers?
A
external factors in the environment that affect of entrain our biological rhythms such as influence of light on the sleep/wake cycle.
6
Q
what are endogenous pacemakers?
A
internal body clocks that regulate many of our biological rhythms such as influence of the suprachaismaric nucleus on the sleep/ wake cycle
7
Q
suprachiasmatic nucleus
A
tiny bundle of nerves located in the hypothalamus in each hemisphere or the brain. One of the primary endogenous pacemakers in mammalian species. Influential in maintaining circadian rhythms much as sleep/wake cycle. It lies above the optic chiasm (where nerve fibers are connected to the eye). Receives information about light directly from this
8
Q
Siffres cave study
A
Michal Siffre spend extended periods in a cave with no light to observe whether his cycles (e.g. sleep/wake cycle) changed, through brain wave activity and tasks.
9
Q
other studies on circadian rhythms
A
Aschoff and Wever convinced a forum of participants to stay in a dark underground bunker for 4 weeks. all but one of the participants s/w cycle extended to 29 hours. Circadian cycle was between 24 to 25 hours. Both this and Siffres study suggest natural s/w cycle might be longer that 24 hours but exogenous factors associated with our 24 hour day entrained this.
Study on cave with clock that went faster opposes this as even though there was no light they couldn’t fit to the changing sleep schedule that went from 24 hours to 22
10
Q
what is the nervous system?
A
our primary internal communication system.
consists of the central nervous system (CNS) and the peripheral nervous system. It communicates using electrical signals.
11
Q
two main functions of the nervous system
A
-collect, process and respond to information in the environment
-to co-ordinate the working of different organs and cells in the body
12
Q
what subsystems is the nervous system divided into?
A
central nervous system
peripheral nervous system
13
Q
what is the central nervous system?
A
consists of brain (center of all consciousness and awareness) and spinal chord (extension of the brain, passes messages to and from brain and connects nerves to PNS, responsible for reflex actions) and is the origin of complex commands and decisions
14
Q
what is the peripheral nervous system?
A
sends information from the CNS from the outside world, and transmits messages from to muscles and glands in the body. subdivided into autonomic nervous system and somatic nervous system
15
Q
what is the autonomic nervous system?
A
governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses
16
Q
what is the somatic nervous system?
A
governs muscle movement and receives info from the sensory receptors
17
Q
what are subdivisions of the autonomic nervous system?
A
sympathetic nervous system and parasympathetic nervous system
18
Q
what is the sympathetic nervous system?
A
a network of nerves that helps your body activate its “fight-or-flight” response.
19
Q
what is the parasympathetic nervous system?
A
a network of nerves that relaxes your body after periods of stress or danger
20
Q
what is the endocrine system?
A
one of the bodies major information systems that instructs glands to release hormones directly into the bloodstream. these hormones are carried towards target organs in the bodies. Communicates via chemicals, and works along side the nervous system.
21
Q
which one is faster- the nervous system or endocrine system?
A
nervous system- electrical signals
22
Q
what does thyroxine do?
A
from thyroid gland- increases heart rate and metabolic rates (increasing growth rates)
23
Q
what is the fight or flight response ?
A
the way an animal responds when stressed. Body becomes physiologically aroused in readiness to fight an aggressor, or in some cases, flee.
24
Q
Fight or flight process explanation
A
endocrine system and ANS work together. when a stressor is perceived, for example you have upcoming exams) the hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch of the ANS. The ANS changes from urs normal resting state (parasympathetic state) to the physiologically aroused state (sympathetic state). Adrenaline is released from adrenal medulla which creates the physiological arousal needed. Examples of responses immediately would be increased heart rate and inhibited digestion. Once the threat has the passed, the parasympathetic branch of ANS works in opposition of the SB, acts as a break and reduces activities in the body that were originally increased such as HR.
25
what are neurons?
nerve cells that process and transmit messages through electrical and chemical signals. There are 100 billion in our body, 80% of them being in our brain.
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whats a sensory neuron?
carry messages from the PNS to the CNS. They have long dendrites and short axons
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whats a relay neuron?
Connect the sensory neurons to the motor or other relay neurons. Short dendrites and long axons
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whats a motor neuron?
connect the CNS to the effectors such as muscles or glands. Long axons and short dendrites.
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structure of a neuron
-vary in size from millimeter to meter.
-cell body includes a nucleus, which contains genetic material of the cell.
-dendrites protrude from the cell body.
-Axon carries the impulse away from the cell body and is covered in a fatty layer of myelin sheath that protects the axon and speeds the electrical transmission.
-nodes of ranvier (gaps in the myelin sheath) are there because if the myelin sheath was continuous it would only slow down the impulse. Forcing the impulse to jump across speeds it up.
-terminal buttons at the end of the axon communicate with the next neuron in the chain across a gap called the synapse.
30
Where are neurons located?
the cell bodies of motor neurons may be in the CNS but they also have long axons that form part of the PNS. PNS clusters called ganglia hold sensory neurons. Relay neurons make up 97% of the neurons and are found in the brain and visual system.
31
Electrical transmission- firing of a neuron
while a neuron is in its resting state it is negatively charged compared to the outside. When a neuron is activated by the stimulus, the inside of the cell becomes positively charged for a split second causing action potential to occur. Creates an electrical impulse that travels down the axon to the end of the neuron.
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hat is synaptic transmission?
process by which neighboring neurons communicate with each other by sending messages across the synapse (gap) that separates them.
33
What occurs during chemical transmission between synapses?
neurons communicate with each other in neural networks. Each neuron is separated by a synapse. Signals within neurons are transmitted electrically, however they are transmitted chemically between each other. When the electrical impulse reaches the end of a neuron (pre-synaptic terminal) it triggers the release of a neurotransmitter from tiny sacs called synaptic vesicles.
34
what is a neurotransmitter?
brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another. They can be broadly divided into those that perform an excitatory function and inhibitory function
35
Why can direction of travel only be one way for neurotransmitters?
hey are released by a pre synaptic neuron terminal and received by a post synaptic receptor site.
36
What is excitation?
when a neurotransmitter (e.g. adrenaline) increases the positive charge of the post synaptic neuron. This increases the likelihood that the post synaptic neuron will pass on the electrical impulse. (fire)
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What is inhibition?
when a neurotransmitter (e.g. serotonin) increases the negative charge of the post synaptic neuron. This decreases the likelihood that the PSN will pass on the electrical impulse. (fire)
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Summation
Decision to fire is based on the summation. Action potential of the PSN is only triggered if the sum of the excitatory and inhibitory signals a any one time reach the threshold. E.g. PSN is inhibitory it is less likely to fire
39
Explain the process of synaptic transmission:
1)electrical impulse reaches the end of the neuron (axon)- (pre-synaptic terminal)
2)triggers release of neurotransmitters from synaptic vesicles
3)diffuses across the synapse to the post synaptic receptor sites on the dendrites of the next neuron.
40
what is localisation of function?
the theory that different areas of the brain are responsible for specific behaviors and processes. For example, the motor area being located in the back of the frontal lobe
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hemispheres of the brain
the brain is divided into two symmetrical halves. Lateralisation- some of our physical and psychological functions are controlled or dominated by a particular hemisphere. Activity on left side of the body is controlled by the right side of our brain and visa versa.
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hemispheres of the brain
the brain is divided into two symmetrical halves. Lateralisation- some of our physical and psychological functions are controlled or dominated by a particular hemisphere. Activity on left side of the body is controlled by the right side of our brain and visa versa. Damages to certain areas may lead to loss of certain functions, such as loss of control over fine movements
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Where is the motor area located?
frontal love, involved in regulating movement
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where is the somatosensory area located?
parietal lobe, processes sensory information such as touch.
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where is the visual area located?
Part of the occipital lobe that receives and processes visual information
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where is the auditory area located?
temporal lobe. concerned with analysis of speech based information.
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What are the language centers of the brain?
wernicke and brocas
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Brocas area responsibility
are of the frontal lobe in the left hemisphere (for most people) responsible for speech production
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Wernicke's area responsibility
area of the temporal lobe (encircling auditory context) in the left hemisphere (in most people)responsible for language comprehension.
-famous Brocas 'tan patient' made him realize Brocas aphasia made people have difficulty with prepositions and conjunctions
-Wernicke found people with wernicke aphasia would produce nonsense words
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evaluation of localisation of function:
-evidence from neurosurgery: neurosurgery is a last resort for mental disorder treatment. cingulotomy involved isolating a region called the cingulate gyrus which has been implicated in OCD. Results showed from follow up after 32 week with 44 people who had surgery: 30% had met the criteria for a successful response and 14% partial. This suggests behaviors such as mental disorders may be localized
-evidence from brain scans: Peterson et al- brain scans showed Wernickes area was active during listening task and Brocas was on reading task. Other study showed semantic and episodic memory reside in the prefrontal cortex. Therefore there is scientific evidence it can be localized
-COUNTERPOINT: 10%-50% of cortex was removed in rats that were learning route in maze. No difference in any areas, shows it is more holistic and localized.
-Language localisation questioned:
-only 2% of scientists think this. Latest FMRI show that language streams have been identified across the cortex, including brain regions such as thalamus and also in the right hemisphere. Suggests more holistic approach
51
evaluation of localisation of function:
-evidence from neurosurgery: neurosurgery is a last resort for mental disorder treatment. cingulotomy involved isolating a region called the cingulate gyrus which has been implicated in OCD. Results showed from follow up after 32 week with 44 people who had surgery: 30% had met the criteria for a successful response and 14% partial. This suggests behaviors such as mental disorders may be localized
-evidence from brain scans: Peterson et al- brain scans showed Wernickes area was active during listening task and Brocas was on reading task. Other study showed semantic and episodic memory reside in the prefrontal cortex. Therefore there is scientific evidence it can be localized
-COUNTERPOINT: 10%-50% of cortex was removed in rats that were learning route in maze. No difference in any areas, shows it is more holistic and localized.
-Language localisation questioned:
-only 2% of scientists think this. Latest FMRI show that language streams have been identified across the cortex, including brain regions such as thalamus and also in the right hemisphere. Suggests more holistic approach
52
What is hemispheric lateralisation?
the idea that the hemispheres of the brain are functionally different and that certain behaviors and mental processes are mainly controlled by one hemisphere rather than the other- e.g. language
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vision in hemispheres
both opposite and same sided. Each eye receives light for the left visual field and the right visual field. The LVF of both eyes is connected to the right hemisphere and the RVF is visa versa. This allows perspective and depth perception.
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evaluation of hemispheric lateralisation
+research: Fink et al used PET scans to identify which brain areas were active during a visual task. P with connected brains were asked to attend to global elements of an image e.g. picture of a whole forest regions of the RH were more active. Finer detail- LH was more active. Suggest that as far as visual processing goes HL is a feature of connected as well as split brain
-Nielsen et al analysed brain scans from over 1000 people 7-29 years found people did use areas for certain tasks but there was no evidence of a dominant side. Suggest notion of right/ left brained people are wrong.
55
What is split brain research?
series of studies (began in 1960s) involving people with epilepsy who had experienced a surgical separation of the hemispheres of their brain (mainly by corpus callosum) to reduce the severity of their epilepsy. This enabled researchers to test lateral functions of the brain in isolation.
56
describe the procedure of Sperry's split brain research
-11 people who had the split brain operation were studied using a set up where an image would be projected into P's RFV (linked to LH), and the same or different into LFV (RH). Normal brain would share the info between both hemispheres giving a complete picture of the world, but split brain people's info cannot be conveyed from one hemisphere to the other.
57
describe the findings of Sperrys split brain research
-when picture was showed to RFV (LH) they could describe what was seen. But nothing was there with LFV. This is because relaying messages from language centers to RH is not possible with a split brain unlike it would be with a connected one.
-although they could not give a verbal label, they could select a matching object out of sight using their left hand (linked to RH). Left hand could also select an object closely associated with the one showed in LFV. If a pinup piture was shown in LFV they would display an emotional reaction but would say they only saw a 'flash of light'.
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what are the conclusions of Sperrys split brain research?
observations showed how certain functions are lateralized in the brain and support the view that the LH is verbal and the RH is silent but emotional.
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evaluation of split brain research.
+research support Gazzinga showed split brain's were better at performing some tasks such a odd one out. In a normal brain, LH's better cognitive strategies are watered down by the inferior RH. This supports Sperrys findings that left brain and right brain are distinct.
-generalization issues: causal relationships are hard to establish. Behavior of split brain P's were compared to neurotypical control group
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evaluation of split brain research.
+research support Gazzinga showed split brain's were better at performing some tasks such a odd one out. In a normal brain, LH's better cognitive strategies are watered down by the inferior RH. This supports Sperrys findings that left brain and right brain are distinct.
-generalization issues: causal relationships are hard to establish. Behavior of split brain P's were compared to neurotypical control group- confounding variable. May be a result of epilepsy rather than split brain.
+ethics: operations were not for the study, and full consent was obtained. However the trauma of the surgery means that P's might not understand the implications they had to agree to. Lengthy tests of years might have become stressful over time.
61
what is brain plasticity
describes the brains tendency to change and adapt as a result of experience and new learning, involving the growth of new connections. As an infant our connection are peaked at around 15,000 per neuron, about twice as many as an adult. As we age, frequently used connections are strengthened and rarely used are deleted (synaptic pruning)
62
what research is the into plasticity?
Maguire et al:
-taxi drivers brains were studies and she found a large amount of 'grey matter' in the posterior hippocampus than in a matched control group. This part of the brain is associated with navigational skills.
-As part of their training, London cabbies must take part in the knowledge test to recall streets and routes
-also found positive correlation between length of time in the job and pronounced structure difference.
-Sane finding was found in partial cortex for medical students after exams.
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Plasticity evaluation
-may have negative behavioral consequences. Evidence of brains adaption to prolonged drug use leads to poorer cog functioning and increased risk of dementia. 60-80% of amputees experience phantom limb syndrome that can be very painful (due to somatosensory cortex cortical reorganization) Shows that it cannot always be beneficial.
+age and plasticity: in general, plasticity reduces with age, but studies found 40 hours of golf training for 40-60 y/o's produced changes in neural representations of movement. FMRI found reduced motor cortex activity in novice golfers compared to control group, suggesting more efficient after training. Suggests plasticity can continue throughout lifespan.
+seasonal change has been observed in animals e.g superchaismatic nucleus.
-cannot base this on humans
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what is functional recovery?
A form of plasticity. Following damage through trauma, the brains ability to redistribute or transfer functions usually performed by damaged areas to undamaged areas. Neuroscientists suggest occur quickly after recovery (spontaneous recovery) then slow down after several weeks or months. Rehabilitative recovery might be needed to aid it further.
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what happens in the brain during recovery?
reorganizing and rewiring synaptic connections close to the area of damage. Secondary neural pathways that do not typically carry out a function are activated to allow functioning to continue.
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what are the three structural changes in the brain that could occur during functional recovery?
axonal sprouting, denervation super-sensitivity, and recruitment of homologous.
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what is axonal sprouting?
growth of new nerve endings which connect with other undamaged nerve cells to form neuronal pathways
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what is recruitment of homologous?
(similar) areas on the opposite side of the brain. Means specific task can still be performed. Example- Brocas area was damaged on the left side of the brain, right side equivalent would carry out its functions. After period of time, functionality can then shift back to the left side.
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what is denervation supersensitivity?
occurs when axons that do a similar job become aroused to a higher level to compensate to the ones that are lost. However, it can have a negative consequence of over-sensitivity on things such as pain.
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functional recovery evaluation:
+real world strength: -contributed to field of neuro-rehabilitation, understanding axonal growth has opened up doors to new therapies tried. E.g. constrain induced movement therapy is used with stroke patients by restraining unaffected area and affected is attempted to use. Shows research into functional recovery is useful as it helps medical professionals know when interventions need to be made.
-level of education may influence recovery rates. Schnieder et al revealed that the more time people with a brain injury has spent in education, the greater the chances of disability free recovery- 40% of those with a DFR had 16 years of education compared to 10% who had 12 years or less. This implies that people with brain damage who have insufficient DFR are less likely to achieve a full recovery
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what is FMRI (functional magnetic resonance imaging)
-method to measure brain activity by getting a person to perform a task.
-work by detecting changes in blood oxygenation and and flow that occur as a result of neural activity
-this is detected through changes in magnetic field
-3D images are displayed showing which areas of the brain are important in certain functions.
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what it EEG (electroencephalogram)
-a record of tiny electrical impulses (so measures electrical activity) within the brain via electrodes.
-By measuring characteristic wave patterns, the EEG can help diagnose conditions such as epilepsy.
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what is ERP (event related potentials)
-through statistical analysis of EEG data, data is filtered out until it is left with the electrophysical response of the brain to a specific cognitive, sensory or motor event.
-EEG on the other hand is the over all neural response, not just the ERP (E.g. presentation of specific stimulus)
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what is a post mortem examination?
the brain is analysed after death to determine whether certain observed behaviors during the persons life time can be linked to structural abnormalities in the brain
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FMRI STRENGTHS
-unlike other scanning techniques such as PET, it does not rely on the use of radiation.
-it is virtually risk free, non invasive and straight forward to use.
-produces images that have high spatial resolution- detail by mm, and providing a clear picture on how brain activity is localized
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FMRI LIMITS
-expensive compared to other neuroimaging techniques.
-Poor temporal resolution- 5 second time lag behind screen and initial firing of neuronal activity.
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EEG STRENGTHS
-useful in studying stages of sleep and in diagnosis of conditions such as epilepsy
-unlike FMRI, it has high temporal resolution (single millisecond)
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EEG LIMITS
-generalized nature of information received.
-not useful for pinpointing the exact source of neurological activity, making it tricky for researchers to distinguish between activities originating in different but adjacent locations.
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ERP STRENGTHS
-as they are derived from EEG'a, they have good temporal resolution.
-They bring much more specificity to the measurement of neural processes that could ever be achieved with EEG data.
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ERP LIMITS
-lack of standardization in ERP methodology between different research studies which makes it difficult to confirm findings.
-in order to establish pure data in ERP studies, background noises and extraneous materials must be completely eliminated, but this might be tricky to achieve
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PM EXAMINATIONS STRENGTHS
-vital to providing a foundation to early understanding of key processes in the brain. Broca and Wernicke both relied on PME in establishing links between language, brain and behavior decades before neuro imaging even became a possibility.
-Also used to study HM's brain to identify areas of damages whihc could be associated with his memory deficits.
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PM EXAMINATIONS LIMITS
-observed damages may not be due to deficits under review but for some other unrelated trauma or decay.
-raise ethical issues of consent from the individual before death. Example HM could not provide informed consent as they lost ability to form memories.
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what are biological rhythms
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)
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circadian rhythms evaluation: (1) strength
+provides us with an understanding of the adverse consequences that occur when they are disrupted. For example, For example, night workers engaged in shift work experience a reduced period of concentration at around 6 in the morning, meaning mistakes and accidents are more likely. Research has also shown a relationship between shift work and poor health. shift workers are 3 times more likely to develop heart disease than people who work more typical work patterns. Shows research into circadian rhythms may have real world application
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circadian rhythms evaluation: (1) strength COUNTERPOINT (limit)
however, these studies use correlational work, meaning it is hard to tell whether desynchronization of the sleep/wake cycle is actually the cause for the negative affects.
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circadian rhythms evaluation: (3) strength
has been used to improve medical treatments. Since they co-ordinate alot of your bodies functions such as heart rate and digestion that rise and fall during the course of day, this led to the field of chronotherapeutics- how medical treatment can be administered in a way that corresponds to a person's biological rhythms. example, aspirin reduces blood platelet activity and can reduce the risk of a heart attack, heart attacks are most likely to occur early in the morning so the timing of taking aspirin matters. research has supported this. this shows circadian rhythm research can help increase the effectiveness of drug treatments
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circadian rhythms evaluation: (4) limitation
generalizations are difficult to make. It seems sleep/wake cycle can vary differentiating on the person so the studies conducted, such as Siffres cave study cannot be generalized since they included small samples of participants. For example, studies showed sleep/wake cycles can range from 13-65 hours, and some people like to sleep early and wake early, while others prefer the opposite. Siffre himself also explained how his s/w cycle has slowed since he was younger. This means it is difficult to use the research data to discuss anything more than averages, which may be meaningless.
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the menstrual cycle- infradian rhythms:
example of an infradian rhythm. Approx 28 days cycle. Although it is an endogenous system, research has shown that it may be influenced by other woman’s cycles. (exogenous) pheromones from armpits (9 woman) were spread to other woman (20) on the upper lip and results showed 68% of woman showed changes to the cycle which brought them closer to the ‘odour donor’
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SAD (seasonal affective disorder) infradian rhythms:
depressive disorder with as seasonal pattern. Usually triggered in winter months as daylight hours become shorter. Specifically Circannual rhythm since it is yearly. Scientists have found this may be due to the hormone melatonin being produced until there is an increase in light, but during winter the lack in light means our body keeps producing melatonin.
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Infradian rhythms evaluation:
+may be explained by natural selection. Synchronization of cycles is shown to have some evolutionary value. Eg our may have been an advantage for woman to me started together and become pregnant at the same time in history. This would allow babies, who have lost their mothers, to have access to breast milk improving their chances of survival
-Methodological short comings: other facts such stress, diet changes exercises etc may have been the reason for this. Confounding variables. This may explain why other studies found it hard to replicated the findings, so not reliable.
+Light box therapy for SAD has an 80% work rate
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Ultradian rhythms: stages of sleep
psychologists have identified 5 stages of sleep that altogether have a span of around 90mins and is characterized by a different level of brain wave activity which can be monitored using an EEG
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describe stages 1 and 2 of the sleep cycle:
light sleep where a person might be easily woken. In stage 1, brain waves are high frequency and have a short amplitude. Alpha Waves. In stage 2, these alpha wave continue but there are occasional changes in pattern called sleep spindles
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describe stages 3 and 4 of the sleep cycle:
Deep sleep, or slow wave sleep. Brain waves are lower frequency and higher amplitude. Difficult to wave someone at this point
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describe stage 5 of the sleep cycle:
REM sleep. body is paralyzed yet brain activity closely resembles that of an awake brain. Theta waves are produced, and eye occasionally move around. Dreams are often experienced here, but can also be experienced in deep slee
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ultradian waves evaluation
+ improved understanding of age related sleep. Sleep scientists have observed SWS reduced with age. Growth hormone is produced during this stage and this is reduced in older people. According to researchers, sleep deficit may explain various issues in old ages such as reduced alertness. This has enabled them to prescribe people with medicines and relaxation techniques. Shows it has practical value.
- research shows there is a significant variation between people. Large differences between some participants were found in terms of duration in sleep stages, particularly 3 and 4. It is such heated these differences are likely to be biologically determinanted. Makes it difficult to describe normal sleep in any meaningful way.
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animal studies and the SCN (endogenous pacemakers)
influence of SCN has been demonstrated through animal studies. DeCoursey et al destroyed SCN connections in the brain for 30 chipmunks who were then returned back to their natural habitat and observed for 80 days. Most of them were killed off by predators, and their sleep/wake cycle disappeared. They were killed off presumably because they were awake when they shouldn't have been.
In another study, mutant hamsters were bread with a 20 hour sleep/wake cycle. When the CNS cells from tissue of the mutant hamsters were transplanted to the normal hamsters, the cycles on the second group defaulted to 20 hours.
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where does the SCN pass info on light and day length that it recieves?
to the pineal gland, behind the hypothalamus. This is another endogenous mechanism guiding the S/W cycle. Increased production of melatonin at night by this gland
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Endogenous pacemakers evaluation
-complex influences on the s/w cycle, not just SCN, and it may obscure other body clocks. Example, research has revealed there are numerous circadian rhythms in many organs and cells like peripheral oscillators. They are influenced by the actions of SCN, but also act independently. Feeding patterns in mice could alter rhythms in cells by 12 hours with un affected SCN
-cannot be studied in isolation. Total isolation studies, such as siffres cave study, are rare. Even his study lack validity due to his lamp being turned on that may have reset his biological clock. Pacemakers and zeitgebers constantly interact so it may make little sense to separate the two for research. Suggests that when researchers isolate one it can lower validity of research.
+similar mechanisms across species in studies to humans brain wise
-enethical study, many animals went on to die
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key exogenous zeitgebers: light
light: can reset bodies main endogenous pacemaker the SCN and therefore plays a role of the sleep wake cycle, and also has indirect influences on key things such as hormone secretion. Study showed light is a powerful EG and may not have to be detected by receptor sites on the eye on its own: light pad on knees and results showed a deviation in P's s/w cycle of up to three hours.
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key exogenous zeitgebers: social cues
at about 6 weeks of age s/w cycle is not random and circadian rhythms kick in and buy 16 weeks babies rhythms have been entrained by schedules imposed by parents.
research on jet lag suggests adapting to local times for eating and sleeping rather than following your own hunger and fatigue is an effective way of entraining circadian rhythms and beating jet lag.
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exogenous zeitgebers evaluation:
-do not have the same effect in all environments: comparison of areas that do not have light all year round e.g. Greenland have the same sleep schedules as people who do even without the presence of light. Suggests s/w cycle is primarily controlled by endogenous pacemakers that can override environmental changes such as light
-evidence challenges: social cues are not effective in resetting biological rhythms- man who was blind from birth had an abnormal s/w pattern of 24.9 hours had exposure to social cues such as regular mealtimes, but this could not be adjusted.
