Biopsychology Flashcards
neurons
nerve cells
the bodys communication system
all over the body
the nervous system is made up of over 100 billion neurons
CNS
central nervous system
PNS
peripheral nervous system
function of the nervous system
It controls the body by:
Taking information from the environment using sensory receptors then sends signals that encode this information intothe central nervous system.
Here the information is processed to work out an appropriateresponse.
Output signals are sent to muscles or glands to activate theresponse
what does the brain do
involved in decision making and interpreting sensory information
what does the spinal cord do
relays information between brain and body
allows the brain to monitor and regulate bodily processes
spinal cord connects to spinal nerves which connect to muscles and glands
contains circuits which allows reflexes to be performed
what does the PNS do
the peripheral nervous system is made up of nerves all over the body outside of the CNS
once it has processed information, the brain can send a message down the spinal cord to activate the peripheral nervous system
activating the peripheral nervous system makes the body do what the brain tell is to
parts of the brain
cerebellum
cerebrum
brain stem
what is the cerebrum
largest part of the brain, divides into four lobes which all have different functions
cerebrum splits down the middle into two hemispheres, each has different specialisms
hemispheres communicate using the corpus callosum
what is the cerebellum
sits at the back of the cerebrum
controls motor skills and balance, coordinates muscles to allow for precise movement
what is the brain stem
regulates function for life
breathing, heartbeat, swallowing
what are the two divisions of the PNS
somatic and autonomic
somatic nervous system function
controls voluntary movement
transmits information to and from the senses and to and from CNS and the outside world
1. Sensory receptors: carry information to spinal cord and brain
2. Motor pathways: allow brain to controlmovement
allows us to carry sensory info to the brain and produce muscle response.
autonomic nervous system function
Transmits information to and from internal organs to sustain life.
Plays an important part of Homeostasis: maintains internal processes
Carries out actions without your conscious awareness (e.g. digestion,heart beat)
Made up of: motor pathways
Sympathetic system (increases bodily activity)
Parasympathetic system (decreases activity)
sympathetic nervous system
involved in fight/flight response
fight/flight: in a scary situation, the sympathetic nervous system prepares you to stay and attack or run away
does this by increasing bodily activity
parasympathetic nervous system
maintains normal bodily activity (homeostasis)
rest/digest
acts as a brake and reduces the activities of the body that have been increased by the SNS
fight or flight
helps an individual to react quickly to a threat
role of adrenaline in the body
Hypothalamusrecognises a threat
Sends a message to theadrenal glands(on top of kidneys)
This triggers the release ofadrenaline(endocrine system)
This prompts physical changes in the body
changes in the body due to adrenaline
Rapid Heartbeat and Breathing: to provide the energy and oxygen to the body that will be needed to fuel a rapidresponse to the danger and to push adrenaline faster around thebody.
Pale or Flushed Skin:blood flow to the surfaceareas of the body is reduced and flow to the muscles, brain, legs, and arms are increased.You might become pale as a result, or your face may alternate between pale and flushedas blood rushes to your head andbrain.
Dilated Pupils:to be more aware and observant of thesurroundings during times of danger. Allows more light into the eyes and results inbetter vision of thesurroundings.
Trembling:In the face of stress or danger, your muscles become tense and primed foraction. This tension can result in trembling orshaking.
Sweating-to regulate temperature/increased blood flow oflimbs
Reduction of non-essential functionsdigestive system, urination,salivation
Glycogen-Glucose-To prepare for energy release from increased activity.
fight or flight - a03 - positive behaviours
suggested that for females, behavioural responses to stress are more characterised by a pattern of tend and befriend
this involves protecting themselves and their young through nurturing behaviours and forming protective alliances with other women
these responses evolved in context of being the primary caregiver of their children
fight or flight - a03 - individual differences may effect flight or fight
genetic basis to sex differences in the fight or flight response
a gene that men have that women dont have can statistically explain why they are more aggressive
fight or flight - a03 - freeze response
prior to fight or flight most animals and humans display the freeze response
this is a stop look and listen response
this is where the animal is hyper vigilant, alert to slightest sign of danger the adaptive advantages of this response for humans are that freezing focuses attention and makes them look for new information in order to makes the best response for that particular threat
fight or flight - a03 - not helpful anymore
physiological responses associated with fight or flight may be adaptive for a stress that requires energetic behavioural response, however the stresses of modern life rarely require such levels of physical activity
the problem is when the stress response is repeatedly activated, for example increased bp thats is characteristic of SNS activation can lead to physical damage in blood vessels which could lead to heart disease
what are the 3 types of neurons
sensory, motor, relay
sensory neurons
these are found in receptors such as the eyes, ears, tongue and skin an carry nerve impulses to the spinal cord and brain
motor neurons
these are found in the CNS and control muscle movements, when they are stimulates the send signals to the muscles which leads to movement
relay neurons
these are found between input and output/response neurons, they are found in the brain and spinal cord and allow other types of neurones to communicate with each other
excitatory response
makes it more likely the next neurone will fire
when the neurotransmitters bind to the receptors on the post-synaptic membrane, the post-synaptic neuron becomes positively charged and an action potential is created.
inhibitory response
makes it less likely the next neurone will fire
when the neurotransmitters bind to the receptors on the post-synaptic membrane, the post-synaptic neuron becomes more negatively charged and an action potential is not created.
summation
whether the overall change of the post synaptic neuron is positive or negative
detailed events in synaptic transmission
The electrical impulse travels down the axon of the neuron.
The impulse reaches the synaptic terminal of the pre-synaptic neuron.
This triggers the vesicles filled with neurotransmitters to move to the edge of the membrane of the pre-synaptic neuron.
The neurotransmitters are released into the synaptic cleft/gap
The neurotransmitters diffuse across the synaptic cleft/gap.
The neurotransmitters bind to the receptors on the post-synaptic neuron membrane.
If the overall charge of the post synaptic membrane is negative, no electrical impulse is created.
If the overall charge of the post synaptic membrane is positive, the electrical signal to be sent down the post synaptic neuron.
The neurotransmitters left in the synapse are then taken back by the pre-synaptic neuron (or broken down by enzymes).
endocrine system
glands and hormones
what does the endocrine system do
supplements the work of the nervous system
regulates cells and organs in the body
network of glands throughout the body that manufacture and secrete chemical messengers known as hormones
endocrine system uses blood vessels to deliver hormone to target site in the body
hormones
chemical circulated in the bloodstream and carried to target sites through the body
hormones affect the target cells
when enough receptor sites are stimulated by the hormone this causes a physiological reaction in the target cell
hypothalamus - brain
stimulate and controls release from pituitary gland
pituitary - brain (anterior ACH)
stimulates adrenal cortex and release of cortisol during stress response
pineal - brain (melatonin)
sleep wave cycles and biological rhythms
thyroid - neck (thyroxine)
responsible for regulating metabolism
adrenal - kidney (adrenal medula)
fight or flight
adrenal - kidney (adrenal cortex cortisol)
stimulates release of glucose to provide the body with energy while supressing immuno response
ovaries - reproductive organs (oestrogen)
pregnancy, menstrual cycle
testes - reproductive organs (testosterone)
muscle growth, males sex characteristics
localisation of function
the theory that specific areas of the brain are associated with particular physical and physiological functions
belief before localisation of function
historically scientists believe that the brain was holistic in its processing - which is to say that all parts were involved in cognition
in 19th century, new thinking emerged that different parts of the brain do different things
phineas gage
died at 36, 12 years after accident
he was working at the tracks, when an iron pole went straight through his skull due to explosion and exited and found 30 yards away
within minutes of injury he sat up and go taken to his house, Gage was fully conscious and talking to bystanders about what had happened
frontal lobe was damaged, the frontal lobe is involved in personality
Gage got an infection and became unconscious but then recovered, Gage lost an eye
3 and 1/2 months after incident he was leading a seemingly normal life
changes in personality and behaviour, employers said he was good at job before therefore did not give him his job back
they said he was rude and swears in inappropriate situations, does not care if he offends others plus does what he wants ignoring others wishes
his friends said ‘he was no longer Gage’
Broca’s area
named after paul broca, who discovered the region while treating a patient referred to as TAN
TAN could understand spoken language but was unable to produce any coherent words and could only say TAN, after his death they did a post mortem and found that he had a lesion in the left frontal lobe, therefore the led broca to conclude that this area was responsible for speech production and people with damage to this area experience brocas aphasia
Wernickes area
found that patients with lesion to wernickes area were still able to speak but were unable to comprehend language, this area is found in the left temporal lobe and is thought to be involved in language processing, produce sentences which are fluent but meaningless
temporal lobe
sound language and memory storage
occipital lobe
vision lobe, distance and depth perception
parietal lobe
sensory perception, spatial
somatosensory cortex
at the front of both parietal lobes sensory info from the skin is presented here
separated from the motor area by a valley called the central sulaus
motor area
controls voluntary movement each hemisphere controls the opposite side of the body, contro, lateral
frontal lobe
personality, language
thinking, reasoning, voluntary muscle movement
pituitary gland
master gland
anterior - front
posterior - back
controls release of hormones to the rest of the body
regulates bodily function
pituitary is controlled by hypothalamus, produces hormones that travel in the blood stream to their target site
either cause a change or stimulate other glands to release hormones
negative feedback, stops hormone levels rising too high this is the bodies way of monitoring itself
self regulated loop - brain is monitoring the blood
A03 - localisation of function - brain scan evidence as localisation
there is a wealth of evidence providing support for the idea that many neurological functions are localised, particularly in relation to language and memory, for instance peterson et al (1988) used brain scans to demonstrate how wernickes areas was active during a listening task and brocas area was active during a reading task, suggesting that different areas of the brain have different functions
A03 - localisation of function - case study evidence
phinneas gage
A03 - localisation of function - lashleys research
Karl lashley’s work suggests that higher cognitive functions such as the processes involved in learning are not localised but distributed in a more holistic way in the brain. lashley removed areas of the cortex (between 10 to 50%) in rats that were learning a maze, no area was proven to be more important that any other area in terms of the rats ability to learn the maze, the process of learning appeared to require every part of the cortex, rather than being confined to a particular area, this seems to suggest that learning is too complex to be localised and requires the involvement of the whole brain
A03 - localisation of function - neurosurgical evidence
the practice if surgically removing or destroying areas of the brain to control aspects of behaviour developed in the 1950s, early attempts such as those pioneered by Walter Freeman who developed the lobotomy, were brutal and imprecise and typically involved severing connections in the frontal lobe in an attempt to control aggressive behaviour
controversially neurosurgery is still used today albeit sparingly in cases of OCD and depression, the success of surgeries like these suggests that symptoms and behaviours associated withs serious mental disorders are localised
who did split brain research into hemispheric lateralisation
roger sperry
summary of split brain studies
corpus collosum joins the two halves of the brain, a commissurotomy is the division of the 2 hemispheres by surgery
sperry studied 11 patients who had this surgery for epilepsy after this sperry asked to study them
left half of brain is specialised for
controls right side of body
viewing objects in right visual field
known as the major hemisphere as it processes language
right half of brain is specialised for
drawing - facial recognition - spatial tasks
controls left side of the body
viewing objects in left visual fields
known as the minor hemisphere as it cannot process language
split brain procedure
subject gazes at a fixation point on an upright translucent screen
slides containing words or images are projected either side of the fixation point for 1/10 of a second
visual recognition
when an object is displayed in the right vf thus processed in the left hemisphere patients can describe it in speech and writing this is because language is in the left hemisphere
when an object is displayed in the left vf thus processed in the right hemisphere patients cannot say what they have but if asked to use the left hand to point to a matching object on the table they can do so while still insisting nothing was seen
two different objects are displayed one to each vf e.g. patients are asked to draw what they see with their left hand and say what was drawn
patients drew what was on the left half of the screen because seen with right brain which controls left hand but said they had drawn what was on the right half of the screen, this is because language uses left hemisphere
naming objects by touch
ppts could not attach verbal labels to objects project in the LVF but they could select a matching object from a grab bag wit their left hand
composite words
ppts would be presented 2 words simultaneously they would then select a key with their left hand from a group of objects but would say bottle
right hemisphere dominates when matching faces
know this because when faces are shown to LVF, it is sent to right hemisphere and the correct matching picture is selected
when shown to RVF it is sent to LHS and the matching picture is not selected
suggest faces in the right hemisphere
when using a composite picture each hemisphere sees half a face
if RVF to left hemisphere, verbal description given
if LVF to right hemisphere, select matching picture
split brain procedure conclusions
when we separate the hemispheres we can clearly see that they act differently
the right hemispheres can recall and identify stimuli but cannot verbalise this
left hemisphere specialised for speech and writing
the right hemisphere is mute cannot speak or write can do stuff but cannot say it
A03 - sperry - original ppts were epileptic
can they be said to represent normal brains
perhaps their brains were somehow different due to the epilepsy
also the control group (not split brain) were non epileptic ppts
A03 - sperry - small sample size
sperry only used 11 split brain ppts, as some people have more lateralised brains than others and some patients had more disconnection of the 2 hemispheres than others, this may mean that individual differences could influence results
A03 - sperry - sex differences
although sperrys work concluded that many functions are lateralised, subsequent research suggests women have less lateralised brains
this will influence the result of brain damages
kimura reported more aphasia in men who had left hemisphere damage that women who had left hemisphere damage
A03 - sperry - reductionist
reductionist of human behaviour, most tasks involved a mixture of left and right brain skulls
e,g, when we hear speech we decode meaning from the words (left hs) and the emotional tone in the voice (right hs)
unfortunately the concept of lateralisation in sperrys work has been taken too literally
A03 - sperry - well controlled and standardised procedure
asked ppts to stare at fixed central point and presenting stimuli only briefly ensured each hemisphere received info from only one visual field
triggers philosophical debate about nature of mind, are our two hemispheres to functionally different that they can be considered two minds
spatial resolution
refers to the capacity a brain scan has to tell you exactly which area of the brain is active
temporal resolution
describes the scans ability to tell you exactly when the activation happened
FMRI
functional magnetic resonance imaging
non invasive brain imaging technology that detects brain activity by measuring changes in blood flow using magnet
can reveal what part of the brain is active during specific functions e.g. ask you to lift your left arm - part of brain lights up
black and white images with parts lighting up - colour depends on activity
this means we can show localisation of function
strength of FMRI
not invasive or risky procedure unless person has metal on them, does not use radiation
very clear picture of brain and parts being used
its is clear when we see brain activity occurring, level o brain activity can be shown by colour, white shows high levels
limitation of FMRI
very expensive process die to how expensive machine is
cant see on the level of individual neurons, because only measures blood flow so hard to tell what kind of brain activity is happening
poor temporal resolution, time lag between image on screen and brain activity
EEG
(electroence phalography)
records electrical activity in the brain through electrodes attached to skull through a skull cap
measure average activity from the action of millions of neurons, providing overall account of brain activity
output is amplified and recorder, recording spontaneous brain activity or activity in response to stimuli, can be used to detect unusual arrhythmic patterns of activity, this can indicate neurological abnormalities such as brain disorder, brain waves also indicate the stage of sleep a person is in
EEG strengths
very cheap compared to other brain scanning techniques
high/quick temporal resolution, can accurately detect brain activity at a resolution of a single millisecond
can give diagnoses e.g. epilepsy characterised by random bursts of activity which make it easily detectable
contributed much to our understanding of stages of sleep
EEG limitations
low spatial resolution (not sure where, cant pick up on deeper structures)
ERP
event related potential
brain activity related to an event
ERP are very small voltage changes in the brain that are triggered by specific events or stimuli
they establish a specific response to a target stimulus, many presentations of the stimulus and the response it generates are then averaged together
any extraneous neural activity from the original EEG recording is filtered out leaving on those responses that are related to a specific task or stimulus
ERP strengths
can identify many different types of ERP’s and the precise role of those in cognitive functions
have excellent temporal resolution and are used widely in the measurement of cognitive functions and deficits
ERP limitations
practical difficulties, small and diffcult to pick out from other electrical activity in the brain, very time consuming to gather meaningful data
not always easy to eliminate background noise and extraneous material
critics have pointed out that there is lack of standardisation in ERP, methodology between research studies which make it hard to confirm findings
Post Mortem Examinations
brains are sliced and scanned, use microscope, digital imaging, can scan slices of brain
microscopic level of details, individual neurons
200 years old
areas of damage within brain are examined after death as a means of establishing the likely cause of behavioural deficit the person suffered
may involve comparison to a neuro-typical brain in order to measure the extent of the difference e.g. brocas areas and wernickes area
causation
the deficit a person displays during their lifetime many not be caused by the deficits found in the brain, so we cannot conclude that the deficit is caused by the damage found in the brain during a post-mortem
extraneous variables
can affect conclusions of post mortem examinations e.g. age, length of time between death and examination. these are confounding factors that make conclusion of such research questionable
consent
ethical issues about informed consent prior to death many pots mortem examinations are carried out on patients with severe psychological disorders who would be unable to provide fully informed consent and yet a post mortem examination has been done on their brain
strengths of post mortem
provide hypotheses for future research and improve medical knowledge
they allow us to see fine details on a neural level, very important for diseases such as Alzheimer’s
provide practical applications, such as brocas work into speech production difficulties
what is brain plasticity
brain can change and adapt over time
research into plasticity: Maguire (2000)
studied brains of london tax drivers, they had greater volume of grey matter in posterior hippocampus than in matched control group, associated with development of navigational skills
london cabis must take a a test called the knowledge which assesses their knowledge of the streets and routes in london
appears that spatial learning alters structure of the taxi drivers brain
draganski (2006)
took brain images of med students 3 months before and after their final exams, learning induced changes occured in posterior hippocampus and parietal cortex presumably as a result of studying for exams
mecheli (2004)
found a larger parietal cortex in the brains of people who were bilingual compared to matched monolingual controls
functional recovery
following physical injury or trauma like a stroke unaffected areas of brain are able to adapt and compensate for damaged areas
healthy brain areas take over function, this process can occur quicker after trauma and then slow down after several weeks or months at this point individual may need rehabilitative therapy
axonal sprouting
growth of new nerve endings which connect with other undamaged nerve cells to form new neural pathways
reformation of blood vessels
when brain is damaged blood vessels get damaged, blood vessels get reformed, new neural pathways are formed because there is blood flow
recruitment of homologous areas
when a similar area of the brain on the opposite side is used to perform a specific task, if brocas area was damaged the right side equivalent would carry out its function after a period of time functionality may shift back to the left side
A03 - plasticity and functional recovery - practical application
understanding processes in plasticity
contributed to field of neurohabilitation
following illness or injury to the brain spontaneous recovery tends to slow down after a few words so physical therapy may be required to maintain improvement in functioning
techniques may include movement therapy and electrical simulation to the brain to counter the deficits and/ or cognitive functioning following a stroke for example
A03 - plasticity and functional recovery - negative plasticity
brains ability to rewire itself can sometimes have maladptive consequences
medina et al (2007) - found prolonged use of marjuana resulted in poorer cognitive functioning as well as an increased risk of dementia later in life
60-80% of amputees develop phantom limb syndrome, experience sensations in the missing limb as if it was still there
sensations are unpleasant painful and are thought to be due to the cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss
A03 - plasticity and functional recovery - age and plasticity
functional plasticity tends to reduce with age, brain has greater ability to reorganise in childhood as it is constantly adapting to new experiences and learning
it was found that 40 hours of golf training produced changes in the neural representation of movement in ppts aged 40-60
using fmri the researcher observed reduced motor cortex activity in the novice golfers compared to a control group
suggesting more efficient neural representations after training
A03 - plasticity and functional recovery - animal studies
early evidence of neuroplasticity and functional recovery was derived from animal studies
Hubel and Wiesel (1963) involved sewing one eye of a kitten shut and analysing the brains cortical response
found that the area of the visual cortex associated with shut eye was not idle but continued to process info from the open eye
A03 - plasticity and functional recovery - cognitive reserve
evidence suggests that a persons educational attainment may influence how well the brain functionality adapts after injury
schneider et al the more time the brain injury patients spent in education (a measure of their cognitive reserve) the greater the chances of a disability free recovery
of the patients who achieved PFR 40% had more than 16 years education whereas 10% had less than 12 years education
Ultradian rhythms
biological rhythms that you have more than once a day e.g. the stages of sleep
stages of sleep
biological rhythms that take less than 24 hours to complete, may often occur more than once in the course of the day
5 distinct stages of sleep that span more than 90 minutes
you complete multiple cycles through the night
each stages has different brain wave activity linked to it
stages 1 and 2
the sleep escalator - beginning of sleep the brain wave patterns are slower and more rhythmic (alpha and theta waves)
stages 3 and 4
involve delta waves which are slower still and have a greater amplitude than earlier wave patterns
in stage 5
REM sleep - the body is paralysed yet brain speeds up significantly in a way that resembles the awake brain, rapid eye movement
A03 - ultradian rhythms - EEG’s are used to record brain wave activity
extremely high temporal resolution it can accurately detect brain activity at a resolution of a single millisecond
not as expensive
low spatial resolution - cannot pinpoint exact source of activity
sleep lap data not representative of normal/ sleep data
A03 - ultradian rhythms - supporting evidence of distinct stages of sleep
Dement and Kleitman (1957)
monitored sleep patterns of 9 adults ppts in a sleep lab, brainwave activity was recorded on an EEG and the researchers controlled for the effects of caffeine and coffee
REM activity during sleep was highly correlated with the experience of dreaming, brain activity varied according to how vivid dreams were
ppts woken during dreaming reported very accurate recall of their dreams
replications of study have noted similar findings
REM sleep is important component of ultradian sleep cycle
A03 - ultradian rhythms - individual differences
problem with studying sleep cycles in the difference observed in people
Tucker et al (2007) found significant differences between ppts in terms of the duration of each stage particularly 3 and 4, this demonstrates that there may be innate individual differences in ultradian rhythms also study was carried out in controlled lab setting so difference cannot be attributed to situational factors
Infradian rhythm
rhythms that take longer than 24 hours (so there is a frequency of less than one a day)
e.g. menstrual cycle or SAD
menstrual cycle
governed by monthly changes in hormone levels which regulate ovulation
refers to the time between the 1st day of a womans period when the womb lining is shed, to the day before the next period
typical cycle approx 28 days
during cycle rising levels of the hormone oestrogen cause the ovary to develop an egg an release it
after ovulation progesterone helps the womb lining grow thicker, readying the body for pregnancy
if pregnancy does not occur, the womb lining comes away and leaves the body
the cycle is an endogenous system but research has suggested that it can be affected by exogenous factors
McClintock (1998)
studied 29 women with a history of irregular periods
samples of pheromones were gathered from 9 of the women at different stages in their menstrual cycle via a cotton pad under their armpit
this was worn for 8 hours to ensure pheromones were picked up, then treated with alcohol and frozen, to be rubbed on the upper lip of other ppts
McClintock effect
on day 1, cotton pads from the start of the menstrual cycle were applied to all 20 women on day 2. given a cotton pad from the second day of the cycle
found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their organ donor
Seasonal Affective Disorder
SAD is in the DSM-5 as a recognised mental disorder
melatonin has been 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 means this secretion last for longer
this is thought to then affect the production of serotonin
A03 - infradian rhythms - real life application
knowledge of how SAD is caused and the factors that have an effect upon it have helped to develop treatments, phototherapy lightbox - that stimulates very strong light in the morning and evening, resetting melatonin levels in people with SAD, relieving symptoms up to 60%
A03 - infradian rhythms - animal studies
most knowledge of pheromones on behaviour is from animal studies, for example much research in animal sexual selection however evidence for the effects on human behaviour remains speculation
A03 - infradian rhythms - methodological problems with mcclintock
small study, 29 women, cant be generalised, also number of extraneous factors, stress, diet, exercise, study offers weak support for concept of pheromones
biological rhythms
all living organisms subject to biological rhythms
exert influence on the ways in the which the body system behaves
our biological rhythms have to stay in tune with the environment to achieve this we have endogenous pacemakers and exogenous zeitgebers which reset this clock to maintain its coordination with the environment
Endogenous pacemakers
the body’s internal clocks that regulate many biological rhythms
suprachiasmatic nucleus
an example of an endogenous pacemaker
the pacemaker influencing the sleep/wake cycle is the SCM
inside the hypothalamus, above the optic chiasm
receives info on light levels directly from the optic nerve even when eyes are closed
we respond to light even when we are asleep
SCN sends info on light levels to the pineal gland, which secretes melatonin when light levels dip
A03 - endogenous pacemakers - chipmunks and mutant hamsters study research support
DeCoursey et al (2000)
destroyed SCN connections in brain of 30 chipmunks
returned to natural habitat, observed for 80 days
sleep/wake cycle disappeared
by end of study significant proportion had been killed
Ralph et al (1990)
bred mutant hamsters with 20 hour sleep/wake cycle
when SCN cells from mutant transferred to normal hamsters, cycles of normal defected to 20 hours
both studies emphasises role of SCN in circadian rhythms sleep/wake cycle
not generalisable and unethical
dangers of disrupted rhythms
Touitow et al (2017) conduced research that has shown teenagers spend increasing amounts of time on electronic media at night. the LED bulbs are enriched with a blue light component very active on the circadian clock
leads to suppression of melatonin secretion and circadian disruption
as a result adolescent sleep becomes irregular, shortened and delayed
in the long run, the combo of sleep deprivation and circadian disruption can lead to cardiovascular disorder of depression
Exogenous zeitgebers
external cues which may affect our biological rhythms e.g. the effect of light on the sleep/wake cycle
light
can reset the endogenous pacemaker SCN
has indirect influence on processes that control hormone secretion and blood circulation
Campbell and Murphy (1998)
light can be detected by skin receptor sites even when the information is not received by the eyes
15 ppts woken at various times, light pad shone on backs of knees
produced a 3 hour deviation in normal cycle
light is a powerful EZ
social cues
initial infant sleep-wake cycle more or less random
by 6 weeks circadian rhythms begin
most babies entrained by 16 weeks
adult imposed patterns a major factor, they decide when an infant sleeps and go to bed i.e. social cues
further evidence for social cues as EZ comes from jet lag - eating and sleeping at the new local time is the fastest way to entrain you to the new clock
air travellers study
found that circadian rhythms of air travellers adjusted more quickly if they went outside more at the destination it was thought to be because they were exposed to the social cues of their new time zone, which acted as a zeitgeber
A03 - exogenous zeitgebers - light exposure good for people with jetlag
light is an ez that can reset our natural clocks so when the people are exposed their clocks reset and they no longer have jetlag, less melatonin less sleepy
+ photobox for light therapy before flight to another country, reset circadian rhythms
A03 - exogenous zeitgebers - case study
Laughton Miles et al - young man, blind from birth, with a circadian rhythm of 24.9 hours
despite exposure to social cues, sleep/wake cycle could not be adjusted
had to have sedatives at night and stimulants in the morning to keep pace with 24 hour world
light is very important as a ez and is more important than social cues
A03 - exogenous zeitgebers - methodological issues in studies
Campbell and Murphy study
hasnt been replicated, other psychologists have been critical of the manner in which the study was conducted and have suggester that there may have been some limited light exposure to the ppts eyes- a major confounding variable
also isolating one ez in this way does not give us insight into the many other zeitgebers that influence the sleep wake cycle and the extent to which these may interact
circadian rhythms
24 hour cycles e.g, sleep-wake cycle and core body temp
circadian rhythms dictate when we should be awake and sleeping
light and darkness act as exogenous zeitgebers
rhythm dip at points in the day strongest sleep drive it 2-4 am and 1-3 pm
if we have sufficient sleep the dips are less intense
daylight tells us to be awake during the day, darkness tells us to go to sleep at night
the work of Siffre
in all of siffre’s studies his free running biological rhythm settled to 23 hours - altered with age (48 - hour)
only thing influencing siffre underground was his internal body clock
left the cave in mid september 1962 but thought it was mid august
suggest human body clock relies on ez to keep it on time
without exogenous factors like light our body clock can extent making us believe the day is longer than it is
A03 - circadian rhythms - research methodology
early research studies of circadian rhythms suffered from an important flaw when estimating the free running cycle of the human circadian rhythm
in most studies, ppts were isolated from variables that might affect their circadian rhythms such as clocks, radios and daylight
however there were not isolated from artificial light because it was believe that dim artificial light would not affect their circadian rhythms, early studies confounded by the presence of artificial light
A03 - circadian rhythms - practical application to shift work
shift work has been found to lead to desynchronization of circadian rhythms and can lead top adverse cognitive and physiological effects research has shown that night shift workers suffer a concentration lapse at 6am, increasing the likelihood of accidents, and shift workers are also three times more likely to suffer from heart disease as a result from the stress of adjusting to sleep/wake cycles
this research has many economic implications, in terms on maintaining worker productivity and preventing accidents in the workplace
A03 - circadian rhythms - applications - pharmacokinetics
y understanding circadian rhythms and their impact on health it can help determine the best time to administer drug treatments
for example the risk of heart attach is greatest in the early morning so drugs can be taken at night, bot not released until when they will be most effective at dusk
this means that there are peak times for administration and dosage of a variety of drugs that treat a range of disorders such as cancer, epilepsy and respiratory issues, that increase their efficacy
A03 - circadian rhythms - support from the cave study
siffre
A03 - circadian rhythms - issues with case study evidence
siffre study was on only one individual therefore impossible to generalise these studies on the whole population also he was 60 years old, factors such as age and gender may have significant impacts on our circadian rhythms
