The Nervous System - breakdown

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Endocrine System

  • major information system 
  • instructs glands to release hormones directly into the bloodstream
  • acts more slowly that the nervous system but is more powerful and widespread

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Fight or Flight response

Part of the autonomic nervous system

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Structure of Neurons

(Stimulis->) Sensory neuron -> Relay neuron -> Motor neuron (effector -> response)

  • Nucleus - contains genetic material 
  • Dendrites - carry impulses to cell body
  • axon - carry impulse away from cell body
  • myelin sheath - fatty layer, protects axon and speeds up electrical transmission
  • nodes on ranvier - speeds up transmission by forcing impulses to jump gaps

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Electric Transmission

  • When a neuron is resting inside the cell it is negatively charged. When activated by a stimulus, it becomes positively charged for a split second. This causes electrical potential to occur where an electrical impulse is sent from the cell.

Synaptic Transmission

  • Signals are transmitted between neurons chemically by synaptic transmission.
  • 1.  Eletrical impulse arrives at the presynaptic terminal
  • 2.  Triggers release of neurotransmitter from synaptice vesicles

Signals within neurons - transmitted electrically

Signals between neurons - transmitted chemically

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Excitation and Inhibitation

  • Excitation - neurotransmitter increases the positive charge of the post synaptic neuron so increases the chance that it will fire and pass on the electrical impulse.  
  • E.g. Adreneline causes excitation
  • Inhibitation - neurotransmitter increases the negative charge of the post synaptic neuron so decreases the chance that it will fire and pass on the electrical impulse. 
  • E.g. Serotonin causes inhibition
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Labelled brain

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Localisation and Function

  • Localisation - functions are specific to different areas of the brain
  • Holism - the brain should be studied as a whole as it all works together to perform tasks
  • Left Hemisphere - language and logic
  • Right Hemisphere - creativity

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Broca and Wernicke's Areas

Broca's area

  • responsible for speech production 
  • Broca's aphasia - slow speech that lacks fluency

Wernicke's area

  • responsible for language comprehension 
  • Wernicke's aphasia - producing nonsense words (neologisms)

Conduction aphasia - a syndrome where a patient can both speak and understand language but misuses words and canot repeat words.

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Localisation and Function Evaluation

  • Evidence from neurosurgey
  • Dougherty et al reported 44 people with OCD, who had had their cingulate gyrus removed, 30% had a successful response and 14% had a partial response. Suggests mental disorders may be localised
  • Evidence from brain scans
  • Petersen et al demonstrated Wernicke's area was active during listening tasks and Broca's area was active during reading tasks.
  • Language localisaion questioned
  • Lashley removed cortex areas in rats that were learning maze routes. No area proved to be more important that the other in the rats ability. It seamed that they needed all areas of the cortex (holism)
  • Case Study
  • Phineas Gage was injured in an explosion and impaled by a metal pole to him left cheek and damaging most of his left frontal lobe. he survived but it affected his personality and he was now quick tempered and rude. Suggests the frontal lobe may be involved in regulating mood.
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Plasticity and Research

  • Plasticity - the brain's tendancy to change and adapt as a result of an experience and learning.
  • During infancy, the brain grows synaptic connections. As we grow up, if we don't use these connections, we lose them. 
  • Synaptic pruning - the connections we use lots get strengthened


  • Maguire studied brain of London taxi drivers and found a higher volume of grey matter in their posterior hippocampus than in a control group. This part of the brain links to spacial awareness and navigation. Positive correlation between more grey matter - longer driving time 
  • Draganski imaged medical students 3 months before and after their final exams and found their posterior hyppocampus and parietal cortex which was related to learning
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Plasticity Evaluation

  • Strengths:
  • Plasticity doesn't decrease sharply with age 
  • Bezzola et al demonstrated how 40 hours of golf training produced neural changes in 40-60 year olds. FMRI showed high motor cortex activity compared to the control group, showing there was still plasticity even in old age.
  • Limitations:
  • possible negative behavioural consequence
  • brains adaption to prolonged drug use leads to poorer cognitive function in later life, and increased chances of dementia
  • 60-80% of amputees have developed phantom limb syndrome. This is thought to be due to cortical recognisation in the somatosensory cortex as a result of limb loss. 
  • Shows the brains ability to adapt to damage isn't always beneficial
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Functional Recovery

  • Functional recovery - a form of plasticity, following damage from trauma, the brain's ability to redistribute or transfer functions usually performed by damaged areas to undamaged areas.
  • Neuroscientists suggest that this process can occur quickly after trauma (spontaneous recovery) and then slows down later. At this point, rehabilitation therapy may be needed.
  • The Process of Recovery
  • Axonal sprouting - the growth of new nerve endings which connect with other undamaged nerve cells to form new neural pathways.
  • Denervation supersensitivity - occurs when axons that do a similar job become aroused to a higher level to compensate for the lost ones. However, pain can be a consequence of the oversensitivity.
  • Recruitment of homologous areas - areas in the opposite side of the brain means that specific tasks can still be performed. 
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Functional Recovery Evaluation


  • real world application
  • contributed to understanding in neurorehabilitation
  • E.g. repeatedly moving an affected limb for stroke patients


  • cognitive reserve
  • level of education may affect recovery rates
  • Schneider et al fiund those who spent longer in education had higher recovery rates
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Hemispheric Lateralisation

  • 2 halves of the brain are functionally different

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Hemispheric Lateralisation Evaluation


  • Fink et al used PET scans to identify which brain areas were active during visual processing tasks. When participants looked at a whole image, regions of thr right hemisphere were active. When looking at elements of an image (e.g. individual trees) the left hemisphere was dominant. 


  • Nielsen et al analysed brain scans from over 1000 people aged 7 to 29 and did find some people used certain hemispheres for certain tasks but there was no evidence of a dominant side
  • this suggests the notion of left and right brained people is wrong
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Split brain study and procedure

  • Sperry
  • studied individuals who had undergone surgey where there corpus callosum and connecting tissue was cut down the middle
  • to control frequent and severe epilepsy


  • An image or word was projected to a patient’s right visual field
  • In image or word was projected to a patient’s left visual field
  • In a normal brain, the corpus callosum would immediately share the information between the hemispheres to get a complete picture.
  • However, in the split brains the information cannot be shared.
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Split brain findings

  • Describing what you see – when a picture is shown to the right visual field, they could easily describe what they had seen. However, if the picture was shown to the left visual field, they couldn’t describe what was seen. This is because the language centre is located in the left hemisphere.
  • Recognition by touch – although patients couldn’t verbally describe what they had seen with their left visual field, they were able to select a matching object from a range of different objects using their left hand. The objects were behind a screen so they couldn’t be seen.
  • Composite words – if 2 words were presented simultaneously on either side of the visual field (e.g. key on the left and ring on the right), the patient would write with their left hand the word key and they would say the word ring.
  • Matching faces – the right hemisphere appeared to be dominant in terms of recognising faces. When asked to match a face from a series of other faces, the picture from the left visual field was consistently selected, while the picture from the right visual field is ignored. When a composite picture made up of 2 halves (1 for each hemisphere) was shown, the left hemisphere dominated in verbal description whereas the right hemisphere dominated in terms of matching the picture.
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Split Brain Evaluation


  • Demonstrated lateralised brain function – Sperry’s work into the split brain has produced an impressive body of research findings, the main conclusion is that the left hemisphere is more geared towards analytic and verbal tasks while the right is more for performing spatial tasks.
  • Strengths of the methodology – use highly specialised and standardised procedures. The image projected would be flashed up for 1/10 of a second so the patient wouldn’t have time to move their eyes across the image to get the information for both visual fields. This allowed Sperry to vary aspects of the basic procedure and ensured that only 1 hemisphere was receiving information at a time. This led him to develop a very useful and well-controlled procedure.


  • Issues with generalisation – we should be cautious of widespread generalisation as there were only 11 people who took part in the medical procedure and all had a history of epileptic seizures. The changes in the brain could have been caused by this
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Brain Scans - FMRI

  • Functional magnetic resonance imaging 
  • detects changed in oxygenated blood flow around the brain 
  • more active brain = more oxygenated blood required


  • doesn't rely on radiation so not overly invasive
  • produces images with high spacial resolution


  • expensive
  • poor temporal resolution due to a 5 second lag which makes it not an actual time image
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Brain Scans - EEG

  • Electroencephalogram
  • measures electrical activity via electrodes fixed to the patient using a skull cap
  • used to show patterns of activity
  • uses alpha, beta, delta and theta waves
  • used in diagnosing epilepsy, tumours and sleep disorders


  • high temporal resolution so very useful tool for diagnosis
  • activity relosution of a millisecond


  • informations is generalised so not useful in pinpointing the exact source of neural activity
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Brain Scans - ERP

  • Event Related Potentials
  • Waves which occur within 100 milliseconds are termed sensory
  • Waves which occur after 100 milliseconds are termed cognitive
  • Uses an EEG to measure small voltage changes to stimuli
  • Demonstrates how human processing is effected by specific stimuli


  • have excellent temporal resolution so used to study cognitive fuctions ( e.g. the working memory)


  • lack of standardised methodology
  • background noise and extraneous material must be completely eliminated, which is difficult (in order to establish pure data)
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Brain Scans - Post Mortem

  • used when a person dies
  • examination of the actual physical brain
  • enables researchers to examine the atanomical structure more closely


  • fundamental for early understanding
  • Broca and Wernicke relied on post mortems to understand language and behaviour links


  • the damage displayed may not link to the specific defecits
  • ethical issues of infromed consent
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Biological Rhythms

  • Distinct patterns of changes in body activity 

  • Endogenous pacemakers - our internal body clocks which control the cardiac rhythms 

  • Exogenous zeitgebers - external changes in the environment

  • 3 types of rhythms:

    • Circadian rhythm - 24 hour cycle 

    • Ultradian rhythm - occur many times a day 

    • Infradian rhythm - occurs less that once a day but more than once (e.g. monthly)

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Siffre's sleep/wake study

  • Siffre’s cave study - a caveman who spent long periods of time underground to study his biological rhythm

    • He was deprived of natural light and sound but had food and water 

    • He resurfaced in mid september (2 months in the caves

    • He repeated this a decade later but spend 6 months in a cave 

    • His free-running biological rhythm (not interfered with by environmental changes) settled to one that was around 25 hours and he continued to fall asleep and wake on a regular schedule 

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Other sleep/wake cycle research

  • Aschoff and Wever convinced a group of participants to spend 4 weeks in a WW2 bunker without natural light 

    • All but 1 participants displayed a 24/25 hour cardiac rhythm (1 was 29 hours) 

  • Folkard studied a group of 12 people who agreed to live in a dark cave for 3 weeks, going to bed when a clock read 11:45pm and waking at 7:45am

    • Over the study the clocks were sped up (without participant knowledge) so a 24 hour day eventually lasted 22.

    • Not a single participant was able to comfortably adjust to the new regime which suggests the existence of a strong free running cardiac rhythm that cannot be easily overridden by environmental changes

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Circadian Rhythm Evaluation

  • Strengths:
  • Practical application to shift work - Increased understanding of the consequences of of disruption (desynchronisation). Night workers on shift work may struggle to concentrate at about 6 in the morning (a circadian trough). Researchers have also suggested a relationship between shift work and poor health - shift workers are 3 times more likely to get heart disease often due to the stress of having to adjust to time rhythms
  • Practical application to drug treatments - Circadian rhythms co-ordinate heart rate and hormone levels this will have an effect on pharmacokinetics which is the action of drugs on the body and how well they are absorbed.  Evidence have shown that at peak times during the day or night, drugs are more effective. This has led to development on timing and doses of medications such as anticancer, respiratory and anti-epileptic drugs.
  • Limitations:
  • Use of case studies and small samples - Studies on the sleep/wake cycle tend to involve small studies. The people included may not be representative of the wider population. This reduced how much it can be generalised. Siffre observed that at the age of 60, his internal clock was slower than when he was a young man. Which shows that even when the same person is involved there are factors that vary 
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Infradian Rhythm - Menstrual cycle

  • Monthly changes in hormones which regulate ovulation 
  • Typical cycle is roughly 28 days 
  • Rising production of oestrogen causes the egg to be released in ovulation 
  • Progesterone helps the womb lining grow thicker ready for pregnancy 
  • When pregnancy doesn’t occur the womb lining is released from the body (menstrual flow) 

Research study - Stern and McClintock

  • Demonstrated how menstrual cycles may synchronise with the influence of other females and their pheromone with a sample of 29 women with irregular periods.
  • Samples of pheromones were collected from 9 women (at different stages of their cycle) via cotton pads placed under their armpit for 8 hours.
  • The pads were then treated with alcohol and frozen.
  • On day 1, pads from the start of the cycle were applied to all 20 women’s upper lip. This was repeated on day to with day 2 pads.
  • 68% of women experienced changes in their cycles due to the odour from the pads. 
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Infradian Rhythm - Menstrual cycle Evaluation


  • Evolutionary basis - it would have been beneficial for our ancestors to menstruate and become pregnant together so newborns could be cared for collectively. However, Schank argued against this saying it would become too competitive as there would be too many females so would produce competition for the highest quality males resulting in potentially less fit offspring. This would make the avoidance of synchrony would be more beneficial. 
  • Confounding variables - such as diet, stress, exercise all affect the pattern of the menstrual cycle. 
  • Animal studies - most of the knowledge is from animal studies. The role of pheromones in sexual selection is well documented. Sea urchins release their pheromones into the waterso nearby urchins will eject their sex cells too. However, human studies are very limited so cannot be greatly generalised. 
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Infradian Rhythm - Seasonal Affective Disorder

  • Diagnosed as a mental disorder on the DSM-5.
  • Describes a disorder where patients display depression symptoms during winter. 
  • It is hypothesised that this disorder is triggered in the winter because of the reduced amount of daylight hours. This means that less melatonin is produced due to a reduction in the amount of daylight. This may have a knock-on affect for the amount of Serotonin the brain produces.


  • Practical application (treatment) - one of the most effective way to treat SAD is with phototherapy. This is a light box that stimulated a strong light. It is thought to reset the melatonin levels. This relieves symptoms in up to 60% of patients. 
  • Placebo effect - in the same study, 30% used a ‘sham negative ion generator’ (they were told it was another form of treatment) and reported an improvement. This casts doubt on the chemical influence of the phototherapy.
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Ultradian Rhythms - sleep cycle

  • 5 stages (4/REM)
  • 1 full cycle spans approximately 90 minutes
  • Measured using an EEG
  • 1 and 2: light sleep where the person may be easily woken. Brainwave patterns start to become slower with alpha waves and then even slower with theta waves. 
  • 3 and 4: involve delta waves which are slower and have a greater amplitude than earlier waves. It is difficult to wake someone at this point. 
  • 5/REM: The body is paralysed but the brain activity speeds up and resembles an awake brain. Stands for Rapid Eye Movement and is fast, jerky eye movements under the eyelids. Dreams are linked with this stage. 


  • Dement and Kleitman monitored the sleep patterns of 9 adults in a sleep lab. Activity was measured on an EEG and caffeine and alcohol levels were controlled for. REM was highly correlated with dreaming and participants woken during dreaming reported very accurate recall of their dreams.  This study has also been replicated to show similar findings. 
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Endogenous pacemakers and the sleep/wake cycle

The Suprachiasmatic nucleas (SCN)

  • A tiny bundle of nerve cells located in the hypothalamus in each hemisphere of the brain. endogenous pacemakers are influential in circadian rhythms
  • nerve fibres connected to the eye in the optic chiasm on their way to the visual area and cerebal cortex. The SCN is located just above the optic chiasm and receives information about light directly. 
  • This continues even when our eyes are closed which enables the biological clocks to adjust to changing patterns of daylight whilst we sleep.
  • The SCN passes the information of light to the pineal gland. During the night the pineal gland increases the production of melatonin. 
  • Animal studiesDeCoursey et al destroyed the SCN connections in chipmunk brains. Their sleep/wake cycles disappeared and many were killed by predators. Ralph et al bred mutant hamsters with a 20 hour cycle, their SCN tissue was put into normal hamster and their cycles changed to 20 hours too.
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Exogenous Zeitgebers and the sleep/wake cycle

Light - light may be detected through the skin receptors when it is not received through the eyes. Campbell and Murphy woke 15 participants at various times and a light pack was shone on the backs of their knees. They managed to produce deviation in the participants sleep/wake cycle by up to 3 hours. 

Social clues - infants' initial cycle is random and at about 16 weeks the child has been entrained. The parents impose schedules onto their children on when they can sleep and eat, etc. This influences their biological clock.

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Endogenous and Exogenous Evaluation


  • beyond the master clock - research has revealed that there are numerous circadian rhythms. These are known as peripheral oscillators. They are found in the adrenal gland, oesophagus, lungs, liver, pancreas and skin. Although they are influenced by the SCN, they can act independently. Damiola et al demonstrated this how changing feeding patterns in mice could change their circadian rhythms by up to 12 hours while the SCN was unaffected. 
  • Ethics in animal studies - problems generalising animal studies to humans but also ethic issues with the animals as they faced significant harm once released back into the wild when their biological clock had been changed. 
  • influence of exogenous zeitgebers may be overstated - Miles et al found a blind man (from birth) with a circadian rhythm of 24.9 hours. Despite exposure to social cues, his sleep/wake cycle didn't alter and therefore he had to have stimulants and sedatives in order to be able to function in the 24 hour world. 
  • Confounding variables - Campbell and Murphey's studies haven't been replicated. It's hard to measure as their may be confounding variables, how do you keep out all light? how do you manage other factors such as caffeine?
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