Central Nervous System

  • Origin of all complex demands/decisions and made up of brain and spinal cord


  • Centre of conscious awareness
  • 4 main areas, cerebrum, cerebellum, diencephalon, and brain stem
  • Cerebrum has frontal lobe, parietal, occipital and temporal lobe
  • 2 hemispheres that communicate
  • Cerebellum - motor skills, balance and coordination
  • Diencephlon - thalamus and hypothalamus

Spinal Cord

  • Relays info between brain and rest of body
  • Connected to rest of body by spinal nerves
  • Circuit of nerve cellsenabling reflexes
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Peripheral Nervous System

  • Transmits messages to and from nervous system
  • Outside brain and spinal cord
  • Connects braind and spinal cord to rest of body and external environment e.g., sensory receptors

Somatic Nervous System

  • Voluntary actions - muscle movement and receives info from senses (also involved in reflexes)
  • 12 pairs cranial nerves and 31 pairs spinal nerves
  • Sensory and motor neurons

Autonomic Nervous System

  • Involuntary actions e.g., breathing

Sympathetic NS - increased arousal, increase HR and blood pressure, and decrease digestion (fight or flight)

Parasympathetic NS - decrease arousal, slow HR and reduce blood pressure, rest and digest

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  • Dendrites - receive signals from neighbour neurons and connected to cell body
  • Cell body - control centre and contains nucleus (contains DNA)
  • Axon - carries nerve impulse away from cell body to synapse
  • Myelin sheath covers axon (insulation to speed up movement) - impulses to jump between Node of Ranvier
  • Soma - cell body containing most of cell's organelles 

Sensory Neuron (PNS) - long dendrites and short axons

  • Carry nerve impulses from sensory receptors to brain and spinal cord
  • Converts sensory info to neural impulses then sent to brain - then translates to sensation + brain responds

Motor Neuron (inside CNS + project axons outside CNS) - short dendrites and long axons

  • Form synapses with effectors (muscles and glands) so controls muscles
  • Motor neurons fire causing muscles to contract-relax when motor nwuron inhibited

Relay Neuron (brain and spinal cord) - short dendrites and short axons

  • Allow communication between sensory and motor neurons (interneurons)
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Synaptic Transmission

Action Potentials

  • Occurs when neuron sends info down an axon away from cell body
  • Explosion of electrical activity - a stimulus causes resting potential to move forwards


  • Electrical impulse travels along axon of pre-synaptic neuron
  • Triggers nerve ending to release neurotransmitters (chem messengers) from vesicles
  • NTs diffuse across synaptic cleft and bind with receptors on membrane of post-synaptic neuron
  • This stimulates post-synaptic neuron to transmit electrical impulse
  • Nts reabsorbed into vesicles of pre-synaptic neuron or broken down by enzymes

Excitation and Inhibiton

  • Excitation - NTs make it more likely next neuron will fire (+charge of PSN increase) e.g., acetylcholine
  • Inhibiton - NTs make it less likely next neuron will fire (-charge of PSN increases) e.g., GABA 
  • Summation - excitatory + inhibitory neurons added together to work out whether or not neuron will fire
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Endocrine System

  • In-charge of slow processes e.g., cell growth
  • Work with nervous system to help body function properly 
  • Network of glands that produce and secrete hormones (chemical messengers that travel in the blood and effect target organs)
  • Hypothalamus – stimulates + controls release of hormones from pituitary gland
  • Pituitary gland – ANTERIOR + ACTH + POSTERIOR = OXYTOCIN – uterus contractions in childbirth
  • Pineal gland – melatonin – biological rhythms e.g., sleep cycle
  • Thyroid gland – thyroxine – metabolism
  • Adrenal gland – medulla = adrenaline/noradrenaline – fight or flight + cortex = cortisol to release glucose – provide energy + supress immune system
  • Ovaries - oestrogen + testes - testosterone – reproduction + sex characteristics
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Fight Or Flight Response

  • Amygdala associates sensory signals with emotions e.g., fear
  • Distress signal sent to hypothalamus, which communicates with rest of body through SNS

SAM - Acute Stress (Sympathetic Nervous System)

  • Signal sent to adrenal medulla via NT - adrenal medulla secretes adrenaline and noradrenaline into blood
  • Causes increased HR and BR, and increased blood sugar
  • When stressor gone, parasympathetic branch dampens response, lowering HR, BR and blood sugar to normal

HPA - Chronic Stress

  • Hypothalamus releases a corticotrophin-releasing hormone into blood
  • Causes pituitary gland to produce and secrete ACTH into blood
  • Stimulates adrenal coretx to produce glucocorticoids
  • Cortisol released into blood - reduces pain, increases energy, decreases immune system and cognition
  • System regulates via negative feedback loop
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Localisation of Function

  • Different areas of the brain are responsible for different processes, behaviours and activities

Visual Centres

  • Visual processing begins in retina
  • Nerve impulses transmitted to brain via optic nerve then terminate in thalamus
  • Thalamus passes info to visual cortex (both hemispheres)
  • Right hemisphere receives input from left side of visual field
  • Different areas of cortex process different types of info e.g., shape, colour, and movement

Auditory Centres

  • Hearing + in temporal lobe of both hemispheres
  • Pathways begin in cochlea - sounds converted to nerve impulses
  • Travel via auditory nerve to auditory cortex
  • Information decoded at brain stem
  • Thalamus acts as relay station + further processes stimulus 
  • Auditory cortex is final destination - sound largely decoded + cortex recognises it and produces response
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Localisation of Function

Motor Cortex

  • Generates voluntary motor movements
  • Located in frontal lobe and precentral gyrus - both hemispheres
  • Right motor cortex control muscles in left side of body
  • Regions located locally (next to each other) e.g., area controlling foot is near area controlling leg

Somatosensory Cortex

  • Detects sensory events
  • In parietal lobe and postcentral gyrus - both hemispheres
  • Produces sensations of touch, pressure, pain and temperature from sensory info
  • Different parts of cortex deal with info from different areas 
  • Info then localises to specific region of body
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Localisation of Function

Broca's Area

  • Named after Paul Broca, french neurosurgeon
  • Evidence came from patient named 'tan' that he treated
  • Couldn't speak or express thoughts in writing
  • Could only say 'tan' but could understand language
  • Studied 8 more patients with left frontal hemisphere damage with similar language defects
  • Patients with similar damage in right hemisphere had different language problems 

Wernike's Area

  • Identified by Carl Wernike, a German neurologist
  • In posterior region of left temporal lobe
  • Patients could produce language but couldn't understand it - Wernike's asphasia
  • Produce nonsense words and have fluent meaningless speech
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Localisation of Function Evaluation

  • Evidence support e.g., Phineas Gage
  • Support into asphasia e.g., Broca and Wernike - damage of these areas
  • Peterson et al (1988) used scans to find Wernike's area was active during listening task and Broca's area active during reading task
  • Lashley (1930) opposed idea and came up with equipotentiality - idea that basic motor and sensory functions are localised but higher mental functions are not - also said that intact areas of cortex could take over responsibility for specific cognitive functions after brain injury
  • Dronkers et al (2007) conducted MRI scan on Tan's brain to confirm Broca's findings - lesion found in Broca's area, and evidence suggested that other areas contributed to failure of speech production


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Hemispheric Lateralisation

  • Some mental processes mainly specialised to either left or right hemisphere
  • Two halves not exactly the same
  • Left hemisphere language dominant, science and maths
  • Right hemisphere dominant for visual motor tasks, art and music
  • Information from left side of body processed in right hemisphere and vice versa
  • Corpus Calossum - bundle of nerve fibres from which one hemispheres sends information to the other (left hemisphere dominant for language but can still describe things seen in left visual field - processed by right hemisphere)

Split Brain Research

  • Corpus calossum cut in epileptic patients to separate hemispheres - commissurotomy
  • Hemispheres no longer able to communicate 
  • Reduce amounts of fits but effects behaviour
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Sperry and Gazzaniga (1967)

  • Standard procedure was to project image in patient's right visual field and then left visual field
  • Slides projected either side of fixation point - one picture per 1/10 second

Describing What You See - picture presented and participant describes what is seen

  • Left visual field = could not describe (often said they saw nothing)
  • Right visual field = could describe what they saw

Tactile Tests - objects placed in left or right hand + asked to describe and choose similar object 

  • Left hand = patients couldn't verbally describe what they felt + choose similar object
  • Right hand = couldn't verbally describe but could select similar object

Drawing - patients shown pictures to left or right visual field and asked to draw it

  • Left visual field = draw with left hand and this was clearer than with tight hand 
  • Right visual field = try to draw with right hand bit never as clear as picture
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  • Split-brain research helped us understand functions of hemispheres
  • Mehtods used in split-brain highky controlled using standardised procedures
  • Limitations to methodology as patients are minority group so care should be taken when generalising - small amount of epileptic patients and epilepsy may be a cause 
  • Theory oversimplifies distinction between hemispheres because in normal functioning brain, hemispheres in constant contact 
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Plasticity and Functional Recovery

  • Plasticity is idea that something can change and adapt e.g., synaptic connections in brain 
  • Bridging - new synapses formed and created through use and new stimuli
  • Pruning - connections lost due to lack of use
  • 15,000 connections when we are 2-3 - double amount in adult brain

Videogames - Kuhn (2014)

  • Participants played Super Mario for 30 mins per day for 2 months + brain development compared with control group
  • Significant differences in grey matter in videogame group, in cortex, hippocampus, and cerebellum

Meditation - Davidson et al (2004)

  • Studied Tibetan monks and compared to non-meditating control group
  • Both groups meditated and electrical sensors fitted to detect brain activity
  • Monks showed significantly higher levels of gamma waves (cooridnate neuron activity)
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Functional Recovery

  • Plasticity allows brain-damaged patients to recover some abilities
  • Other, healthy parts of the brain are unmasked and can 'take over' roles of the damaged parts
  • Unmasking - dormant synapses which have not received enough input to be active open connections to compensate for damaged areas

Axonal Sprouting

  • Healthy axons sprout new nerve endings that connect to other pathways in nervous system
  • Used to strengthen existing connections or repair damaged neural pathways to restore them to full functionality

Reformation of Blood Vessels

  • Blood vessels reformed to ensure brain functions in affected areas

Recruitment of Homologous Areas

  • Similar areas on opposite hemisphere of brain recruited for specific tasks
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Plasticity Research Support and Evaluation

London Taxi Drivers - Maguire et al (2000)

  • Have to pass London Knowledge Test where they have to learn routes around London
  • Hippocampus had significantly more grey matter than control group - spatial and navigation skills
  • Positive correlation between time in job and amount of grey matter

Medical Students - Draganski et al (2006)

  • Imaged brain 3 months before and after final exams and significant changes in posterior hippocampus and parietal cortex
  • Research support
  • Used in neurorehabilitation to help brain-damaged patients
  • Plasticity may reduce with age (Elbert - better in children) BUT golf training improved neural representations in 40-60 year olds
  • Functional recovery differs depending on time in education (40% brain damage recovery rate for those in education for 16 years compared to 10% in those in for 12 years)
  • Negative effects e.g., phantom limb syndrome
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Functional Magnetic Resonance Imaging (fMRI)

  • Detects changes in blood oxygenation and flow
  • Activation maps show which areas involved in different processes
  • Risk free, non invasive
  • High spatial resolution (small measurements detected)
  • Low temporal resolution (slow to detect changes)
  • Causation - no direct measure of neural activity 
  • Expensive
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Electroencephalogram (EEG)

  • Measures electrical activity via electrodes
  • Shows brain activity through wave patterns
  • Clinicians use to diagnose disorders with unusual rhythms like epilepsy
  • Non-invasive
  • Diagnosis help
  • High temporal resolution (real-time)
  • Low spatial resolution (no specific areas)
  • Cannot measure deeper regions e.g., hypothalamus
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Event Related Potentials (ERPs)

  • Similar to EEG but uses statistical averaging (present stimulus many times)
  • Brainwaves triggered by certain events 
  • Eliminate extraneous activity
  • High temporal resolution 
  • Not easy to completely eliminate background noise so lots of trials needed
  • Lack of standardisation between studies 
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Post Mortem Examination

  • Analysis of brain following death
  • Examine people with rare disorders to determine whether damage to brain caused disorder
  • Detailed description of anatomical and neurochemical aspects
  • Essential in early research
  • Cannot determine causation
  • Extraneous variables e.g., medication
  • Ethical issues e.g., consent
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Circadian Rhythms

  • Biological rhythm operating in 24-hour cycle e.g., sleep-wake cycle and core body temperature

Sleep-Wake Cycle

  • Dictates when we should sleep and be awake
  • regulated by endogenous pacemakers and exogenous zeitgebers e.g., light
  • Experience 2 sleep dips (most sleepy)- 2-4am and 1-3pm
  • Circadian clock in suprachiasmatic nucleus (SCN) in hypothalamus
  • SCN receives info about light levels from optic nerve
  • When dark, SCN stimulates pineal gland to produce melatonin (linked to sleep), and when light, its production is inhibited

Body Temperature

  • Lowest around 4:30am and highest at 6pm
  • Sleep begins when temp drops and ends when temp rises - alertness
  • Small drop occurs 2-4pm, explaining sleep dip
  • Children showed better recall of story when read to them at 3pm compared to 9pm (cognitive abilities)
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Michel Siffre (Case Study)

  • AIM - investigate free-running circadian rhythms in absence of external cues
  • PROCEDURE - 2months and 6months in caves with no external cues e.g., lamps or clocks (only light was dim and artificial)
  • FINDINGS - when first resurfaced on 17th September 1962, he believed it was 20th August - 25-hour circadian rhythm both times
  • CONCLUSION - free-running circadian rhythms still regular but are longer, and normal ones controlled by endogenous pacemakers and exogenous zeitgebers

Ashcoff and Wever (1976)

  • Individuals in WWI bunker
  • 4 weeks in bunker without external cues
  • All but one had a rhythm of between 24-25 hours and other one of 29 hours
  • Natural sleep-wake cycle is longer than 24 hours
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  • Practical applications to shift work - increase productivity and reduce accidents as least concentration at 6am
  • Practical applications to drug therapies - certain times that drugs more effective
  • Research support into importance of external factors on circadian rhythms
  • Limited control of factors in studies e.g., artificial light in Michel Siffre's study - studies show artificial light can manipulate rhythm and reset body clock each day
  • Studies on small samples and individuals so not representative
  • Individual differences - Czeisler et al (1999) found they can vary in length from 13 to 64 hours and Duffy et al (2001) found differences in cycle onset e.g., morning and evening people 
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Ultradian Rhythms

  • Cycles that last less than 24 hours e.g., sleep stages

Sleep Stages

  • 5 stages of 90 mins + number of cycles depends on time asleep
  • Studied using EEGs
  • Stage 1 - 4-5% of time and alpha and theta waves - light sleep, HR and breathing slow, muscles relax and occasional twitching, and easily woken
  • Stage 2 - 45-55% of time and theta waves - HR low, slight decrease in temp, and still easily woken
  • Stage 3 - 4-6% of time and delta waves - entering deep sleep, brainwaves slow, and harder to wake
  • Stage 4 - 12-15% of time and delta waves - very deep sleep, hard to wake, limited muscle activity and low metabolic rate
  • Stage 5 - 20-25% of time and brainwaves speed up (similar to awake), dreaming occurs, muscles relaxed (paralysed), and HR increases and breathing rapid and shallow

Basic Rest-Activity Cycle (Kleitman)

  • 90 min cycles - period of alertness followed by fatigue
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  • Research support ogf BRAC - Ericsson found elite violinists played for 90 mins and then regularly napped
  • Individual differences in sleep patterns - Trucker (2007) found differences in sleep duration, time to fall asleep, and time in each stage - participants in strict lab conditions so assume differences were biological
  • Sleep stage research is unrealistic - unfamiliar environment, equipment and nerves may affect sleep
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Infradian Rhythms

  • Cycle of duration over 24 hours e.g., maenstrual cycle

Menstrual Cycle

  • Governed by endocrine system and monthly changes in hormones regulate it 
  • Oestrogen causes egg to develop and be released
  • Progesterone increases thickness of lining of womb
  • Cycle begins on day 1 of period and lasts around 28 days - external factors e.g., light and pheromones affect it 

McClintock and Stern (1998)

  • Studied 29 women with irregular periods
  • Cotton pad places under arms of 9 women for 8 hours to collect pheromones
  • Pads treated before being placed on upper lip of other participants
  • 68% women experienced changes in cycle moving them closer to cycle of donor 
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Seasonal Affective Disorder and Evaluation

  • Type of depressive disorder
  • Seasonal pattern of onset - 'winter blues' - symptoms present in winter - limited daylight
  • Linked to hormone melatonin - when there is a lack of light in the morning, melatonin produced for longer so less serotonin produced
  • Research into SAD has practical application as lightbox given and relieves symptoms in 60% of sufferers - BUT other research shows no more effective than placebo
  • Evolutionary advantage to menstrual synchrony as newborns all looked after together increasing survival chance BUT questioned as it would increase competition for males 
  • Methodological issues in synchronisation studies - other variables e.g., stress, diet and exercise have effects - and study relied on self report of small sample
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Endogenous Pacemakers

  • Internal body clocks that regulate bodily rhythms e.g., sleep-wake cycle

Suprachiasmatic Nucleus

  • Main body clock
  • Tiny cluster of nerve cells in hypothalamus, above optic chiasm
  • Light detected by photoreceptors in retina and travel along optic nerve, and SCN receives info (even when eyes closed)

Pineal Gland

  • Works with SCN
  • Info about light passed from SCN to pineal gland
  • Produce melatonin when dark and inhibit production when light
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Chipmunks - Decoursey et al (2000)

  • 30 chipmunks had SCN damaged and put back in wild
  • Sleep-wake cycles disappeared and many died due to being awake at vulnerable times 

Hamsters - Morgan et al (1955)

  • Bred hamsters to have circadian rhythm of 20 hours
  • Neurons from SCN of these hamsters inserted into normal ones and their circadian rhythm altered to 20 hours - imposed pattern onto them
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Exogenous Zeitgebers

  • External cues that regulate rhythms (zeitgeber = time maker)


  • Big influence on SCN and can reset it (influences sleep-wake cycle)
  • Campbell and Murphy (1988) found light detected by body by skin receptors
  • 15 participants woken in night and had lights shone onto back of knees
  • Some cycles deviated by up to 3 hours

Social Cues

  • Meal times and social activities act as external cues
  • Infants begin with random sleep-wake cycle but get into routine
  • Individuals can compensate lack of sleep by responding to social cues
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  • Research support for role of endogenous pacemakers and exogenous zeitgebers
  • Real life application of exogenous zeitgebers e.g., exposure to light on flights reduces jetlag
  • Animals used in studies and were harmed so ethical issues raised and generalisability is questioned
  • Generalisability also questioned when looking at Siffre (case study)
  • Many studies are isolated (looking at one) but in real life they act together, so lacks validity
  • Influence of exogenous zeitgebers overstated as found in studies of blind people and people in Arctic regions
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