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Flashcards in Biopsychology Deck (19):

The nervous system

Consists of the central nervous system and peripheral nervous system - specialised network of cells in the human body and is our primary internal communication system. Has two main functions:
- to collect, process and respond to information in the environment
- to co-ordinate the working of different organs and cells in the body
Subdivided into the central nervous system (CNS) and the peripheral never system (PNS)


The nervous system consists of:

Central nervous system (CNS)

Consists of the brain and the spinal cord
Brain = the centre of all conscious awareness - outer layer of the brain is the cerebral cortex - highly developed in humans and is what distinguishes our higher mental functions - brain is divided into two hemispheres
Spinal cord = extension of the brain - responsible for reflex actions
Passes messages to and from the brain and connects nerves to PNS


The nervous system consists of:

Peripheral nervous system (PNS)

Transmits messages to and from the central nervous system. Further subdivided into:
- Autonomic nervous system (ANS) = governs vital functions in the body e.g breathing, heart rate - divided into sympathetic and parasympathetic nervous system
- Somatic nervous system (SNS) = controls muscle movement and receives information from sensory receptors


The endocrine system

A major information system that instructs glands to release hormones directly into the bloodstream. These hormones are carried towards target organs in the body

Works alongside the nervous system to control vital functions in the body - acts more slowly than the nervous system, but has widespread, powerful effects

Various glands in the body produce hormones - are secreted in the bloodstream and affect any cell in the body that has a receptor for that particular hormone

Major endocrine gland is the pituitary gland - located in the brain - often called the 'master gland' = controls the release of hormones from all the other endocrine glands in the body


Fight or flight

Endocrine and autonomic nervous system (ANS) work together during a stressful event - when a stressor is perceived, the hypothalamus (in the brain) triggers activity in the sympathetic branch of the autonomous nervous system - changes from its resting state to the physiological aroused state - stress hormone adrenaline is released into the bloodstream - triggers physiological changes in the body which leads to fight or flight response
Once the threat has passed, the parasympathetic nervous system returns the body to its resting state



Are nerve cells that process and transmit messages through electrical and chemical signals. Three types of neurons:
- Motor neuron = connect the CNS to effectors such as muscles and glands - have short dendrites and long axons
- Sensory neuron = carry messages from the PNS to the CNS - long dendrites and short axons
- Relay neuron = connect the sensory neurons to the motor and other relay neurons - short dendrites and short axons


Structure of a neuron

Neurons vary in size but share same basic structure - cell body (soma) includes a nucleus which contains the genetic material of the cell
Branch-like structures called dendrites protrude from the cell body = carry nerve impulses from neighbouring neurons towards the cell body
Axons carry away impulses from the cell body down the length of the neuron = covered in a fatty layer called myelin sheath that protects the axon and speeds up electrical transmission of the impulse


Electrical transmission

The firing of a neuron. When a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside. When the neuron is activated by a stimulus, the inside of the cells becomes positively charged for a split second causing an action potential to occur - creates an electrical impulse


Synaptic transmission

The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap that separates them


Chemical transmission - synapses

Each neuron is separated from the next by a tiny gap called the synapse
Signals within neurons are transmitted electrically however signals between neurons are transmitted chemically across the synapse
When the electrical impulse reaches the end of the neuron, it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles
Once the neurotransmitter crosses the gap, it is taken up by the post synaptic receptor site onto the next neuron
Chemical messages is converted back into an electrical impulse and the process of electrical transmission begins



Are chemicals that diffuse across the synapse to the next neuron in the chain
Several neurotransmitters have been identified - each has its own specific molecular structure that fits perfectly into a post-synaptic receptor site, like a lock and key - each has specific functions


Excitation and inhibitation

Neurotransmitters either have an excitatory or inhibitory effect on the neighbouring neuron
Adrenaline = generally excitatory, increasing the positive charge of the post-synaptic neuron, making it more likely the neuron will fire
Serotonin = generally inhibitory, increasing the negative charge of the post-synaptic neuron, making it less likely the neuron will fire
Dopamine = is an unusual neurotransmitter as it is less equally likely to have excitatory or inhibitory effects on the next neuron in the chain


Localisation of function

When specific areas of the brain are linked with specific physical and psychological functions - if an area of the brain is damaged through illness or injury, the function associated with that area is also affected

Brain is divided into two hemispheres = left and right
It is lateralised - physical and psychological functions are controlled by a particular hemisphere e.g left side of the body is controlled by the right hemisphere and vice versa

Outer layer of the brain = cerebral cortex - covers in the inner part of the brain, 3mm thick and is what separates us from lower animals as it is highly developed

Cortex of both hemispheres is divided into four lobes -
- motor area = back of the frontal lobe - controls voluntary movement - damage results in loss of control over fine motor movements
- somatosensory area = front of parietal lobes - processes sensory information from the skin (touch, heat)
- visual area = in the occipital lobe at the back of the brain - each eye sends info from the right visual field to the left visual cortex, vice versa
- auditory area = in the temporal lobe - analyses speech based information - damage may produce partial hearing loss

Broca's area = identified by Broca (1880s) in the left frontal lobe - damage in the area causes Broca's aphasia - characterised by speech that is low and lacking in fluency - Broca's patients might have a difficulty finding words and naming certain objects
Wernicke's area = identified by Wernicke (1880s) in the back of the temporal lobe - patients produce language but have problems understanding it, so they produce fluent but meaningless speech - patients with Wernicke's aphasia will often produce non-sense words as part of the content of their speech


Localisation of function - Evaluation

+ Localisation theory = brain scan evidence - e.g Peterson et al. (1988) used brain scans to show activity in Wernicke's area during a listening task and in Broca's area during a reading task - suggests areas of the brain have different functions - provides scientific evidence of localisation of function

+ Localisation theory = support from neurological evidence - surgically removing or destroying parts of the brain to control aspects of behaviour was developed in the 1950s - though these early attempts were brutal - Dougherty et al. (2002) reported 44 OCD patients who had surgery - at a 32 week follow up, one third met the criteria for successful response to surgery and 14% for partial response - success of such procedures suggests symptoms and behaviours associated with serious mental disorders are localised

- Support from case studies = unique cases of neurological damage support localisation theory, such as the case of Phineas Gage who received serious brain damage in an accident - damage to the brain affected his personality - changed from calm to quick tempered - change in Gage's temperament following the accident suggests the frontal lobe may be responsible for regulating mood

- Neural plasticity = challenge to localisation theory - when the brain has become damaged and a function has been compromised or lost, the rest of the brain is able to reorganise itself to recover the function - what happens is other areas of the brain 'chip in' so they same neurological action can be achieved - although this does not happen every time, there are several documented case studies of stroke victims recovering abilities seemingly lost as a result of illness


Plasticity and functional recovery of the brain

Brain plasticity = the brain is 'plastic' - during infancy, the brain experiences a rapid growth in synaptic connections - as we age, rarely used connections are deleted and frequently used connections are strengthened - synaptic pruning - neural connections can change or be formed at any time, due to learning and experience

Research support - Maguire et al. (2000) = found significantly more volume of grey matter in the posterior hippocampus in London's taxi drivers than in a matched control group - this part of the brain is linked with the development of spatial and navigational skills - as part of their training, London drivers take a test called 'the knowledge' to asses their recall of city streets and possible routes - this learning experience alters the structure of the taxi driver brains - the longer they had been in the job, the more pronounced was the structural difference

Functional recovery of the brain after trauma - is an example of neural plasticity - healthy brains take over functions of areas damaged, destroyed or even missing - neuroscientists suggest this process occurs quickly after trauma and then slows down - the brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage - secondary neural pathways that would not typically be used to carry out certain functions are activated or 'unmasked' to enable functioning to continue

Further structural changes in the brain may include:
- Axon sprouting = growth of new nerve endings which connect with other undamaged cells to form new neuronal pathways
- Reformation of blood vessels
- Recruitment of homologous (similar) areas on the opposite side of the brain to perform specific tasks


Plasticity and functional recovery of the brain - Evaluation

+ Plasticity and recovery research = practical application - understanding processes involved in plasticity has contributed to the field of neurorehabilitaton - techniques include movement therapy and electrical stimulation of the brain to counter deficits to cognitive functioning experienced following a stroke - shows that although the brain may have the capacity to 'fix itself' to a point, this process requires further intervention if it is to be successful

+ Support for neural plasticity = from animal studies - Hubel and Wiesel (1963) sewed one eye of a kitten shut and analysed the brains cortical responses - the area of the visual cortex associated with the eye shut was not idle but continued to process information from the open eye - study demonstrates how loss of function leads to compensatory activity in the brain - evidence of neural plasticity

- Neural plasticity = potential negative consequences - brain's ability to rewire itself can have maladaptive behavioural consequences - e.g prolonged drug use can result in poorer cognitive functioning and increased risk of dementia - also, 60-80% of amputees develop phantom limb syndrome - continued experience of sensations in the missing limb, usually painful and thought to be due to reogranisation in the somatosensory cortex - such evidence suggests the structural and physical processes involved in functional recovery may not always be beneficial

- Relationship between age and plasticity is complex - functional recovery tends to reduce with age - the brain has a greater propensity for reorganisation in childhood as if it constantly adapts to new experiences and learning - however, Bezzola et al. (2012) demonstrated how 40 years of golf training produced changes in the neural representation of movement in participants aged 40-60 - shows that neural plasticity does continue throughout our lifespan


Split-brain research into hemispheric lateralisation

Split brain research = concerns behaviour controlled by just one hemisphere - language is an example of hemispheric lateralisation - usually controlled by the left hemisphere

Split brain study - Sperry (1968) = sought to demonstrate that the two hemispheres were specialised for certain functions and could perform tasks independently of one another - normally the hemispheres are connected by the corpus callosum - a commissurotomy is an operation to cut the corpus callosm and is sometimes performed to control epileptic seizures

Sperry created a procedure to test his split brain patients - An image or word is projected to a patients right visual field processed by the left hemisphere - in the normal brain, the corpus callosum 'shares' information between both hemispheres - in the split brain the information cannot be conveyed from the chosen hemisphere to the other

RVF = patient easily describes what is seen - can't decide objects in LVF because RH lacks
LVF = patients says 'there's nothing there'

Recognition by touch - objects shown to the LVF = could not name them but could select a matching object using left hand - could also select an object that was associated with the image presented to the LVF - in each case the person could not verbally identify what they had seen (because the LH is needed for this) but could understand what the object was (using the RH)


Split brain research into hemispheric lateralisation - Evaluation

+ Split brain research = shows lateralised brain functions - left hemisphere is analytical and verbal and the right is adept at spatial tasks and music - right hemisphere can only produce basic words and phrases but contributes emotional content to language - recent research suggests this distinction with one hemisphere can also be carried out by the other

+ Methodology that Sperry used - Sperry's carefully standardised procedure of presenting visual information to one hemispheric field at a time was quite ingenious - Participants stared at a fixed point with one eye - an image was flashed up for 0.1 seconds, so the patient had no time to move their eyes over the visual field or both sides of the brain - allowed Sperry to vary aspects of the basic procedure and ensure only one hemisphere received information at a time - a very useful and well controlled procedure

+ Sperry's work started a debate about the nature of the brain - Sperry's work triggered a theoretical and philosophical debate about the nature of consciousness and the degree of communication between the two hemispheres in everyday functioning Pucetti (1977) suggested the hemispheres are so functionally different they represent a form of quality in the brain - others argued the two hemispheres are highly integrated and work together in most tasks - showing value to Sperry's work

- Generalisation in relation to Sperry's work - Many researchers have said these findings cannot be widely accepted, as split-brain patients are such as unusual sample of people - only 22 patients took part in all variations and all had a history of seizures - this may have caused unique changes in the brain that influenced the findings - this limits the extent to which the findings can be generalised to normal brains, reducing the validity of the conclusions


Ways of studying the brain

Often used for medical purposes in the diagnosis of illness - often used to investigate localisation to determine which parts of the brain do what

FMRI = detects changes in blood oxygenation and flow that occur due to neural activity in specific brain areas - when a brain area is active it consumes more oxygen and blood flow is directed to the active area - FMRI produces a 3D image showing which parts of the brain are active and therefore must be involved in particular mental processes
+ It is non-invasive = FMRI does not rely on the use of radiation and is safe - also, produces images with high spatial resolution, showing detail by the millimetre - means FMRI can provide a clear picture of how brain activity is localised
- It is expensive = compared to other techniques and can only capture a clear image if the person stays still - also, it has poor temporal resolution because of 5-second lag between initial neural activity and image - means FMRI may not truly represent moment to moment brain activity

EEG = measures electrical activity within the brain via electrodes using a skull cap - the scan recording represents the brainwave patterns generated from millions of neurons - shows overall brain activity - EEG is often used as a diagnostic tool e.g indicate abnormalities such as epilepsy, tumours, sleep disorders
+ Contributed to our understanding = of the stages of sleep - also has extremely high temporal resolution - can detect activity at a resolution of a single millisecond
- Produces a generalised signal from thousands of neurons - also, it is difficult to know the exact source of neural activity - EEG cannot distinguish activity of different by adjacent neurons

ERPs = are what is left when all extraneous brain activity from an EEG recording is filtered out - done using a statistical technique, leaving only those responses that relate to the presentation of a specific stimulus or performance of a certain task - ERPs are types of brainwave that are triggered by particular events - research has revealed many different forms of ERP and how these are linked to cognitive processes - perception, attention
+ Very specific measurement of neural processes - are more specific than can be achieved using raw EEG data - also have excellent temporal resolution especially compared to FMRI
- Lack of standardisation - in methodology between studies - makes it difficult to confirm findings in studies involving ERPs - also, background noise and extraneous material must be completely eliminated which is not always easy to achieve

Post-mortem examinations = technique involving the analysis of a persons brain following their death - areas of the brain are examined to establish the likely cause of a deficit or disorder that a person suffered in life
+ Provided the foundation for understanding the brain - Broca and Wernicke both relied on post-mortem studies - also improves medical knowledge - help generate a hypothesis for further study
- Causation may be an issue - observed damage in the brain may not be linked to the deficit under review but to some other related trauma or decay - also raises ethical issues of consent from the patient before death - patients may not be able to provide informed consent