AQA biopsychology

The two roles of the human nervous system

To collect, process and respond to information in the environment

to co-ordinate the working of different organs and cells in the body

the two subsystems of the nervous system

peripheral nervous system

central nervous system

The divisions of the peripheral nervous system

autonomic nervous system

somatic nervous system

The autonomic nervous system function

governs all vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses

Split into the sympathetic nervous system and the parasympathetic nervous system

The parts of the central nervous system

The brain: centre of all conscious awareness, the outer layer is called the cerebral cortex and is divided into two hemispheres

The spinal cord: an extension of the brain, responsible for reflex actions

The peripheral nervous system

sends information to the CNS from the outside world and transmits messages from the CNS to muscles and glands

The central nervous system

is the origin of all complex commands and decisions

The endocrine system

One of the body's major information systems that instructs glands to release hormones directly into the bloodstream, these hormones are carried towards target organs in the body

Gland

An organ in the body that synthesises substances such as hormones

Hormones

chemical substances that circulate in the bloodstream and only affect target organs, they are produces in large quantities but disappear quickly

The pituitary gland

The main endocrine gland, often called the master gland because it controls the release of hormones from all other endocrine glands in the body

Fight or Flight response

1. when a stressor is perceived the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system

2. The ANS changes from its normal resting state (the parasympathetic state) to the physiologically aroused sympathetic state

3. The stress hormone adrenaline is released into the bloodstream - adrenaline triggers physiological changes in the body e.g. increased heart rate, necessary for the response

4. once the threat has passed the parasympathetic nervous system returns the body to its resting state, it acts as a break and reduces the activities of the body that were increased by the actions of the sympathetic branch, sometimes referred to as the rest and digest response

sympathetic state

- increases heart rate

- increases breathing rate

- dilates pupils

- inhibits saliva production

- contracts rectum

Parasympathetic state

- decreases heart rate

- decreases breathing rate

- contracts pupils

- stimulates digestion

- stimulates saliva production

- relaxes rectum

The structure of a neuron

- Vary in size from less than a millimeter to up to a meter long

- the cell body (or soma), dendrites, axon, myelin sheath, nodes of Ranvier and terminal buttons

Cell body (soma) of a neuron

includes a nucleus, which contains the genetic material of the cell

Dendrites

branch-like structures that protude from the neuron cell body

Axon

carries the impulses away from the cell body

Myelin sheath

fatty layer that protects the axon and speeds up chemical transmission

Nodes of Ranvier

where the myelin sheath is segmented to maintain the speed of chemical transmission

Terminal buttons

Communicate between neurons

electric transmission - firing of a neuron

1. when a neuron is in a resting state the inside of the cell is negatively charged compared to the outside

2. when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur

- this creates an electrical impulse that travels down the axon towards the end of the neuron

types of neuron

motor neurons, sensory neurons and relay neurons

neural networks

Groups of neurons communicating with each other

The synapse

includes the space between the neuron (called the synaptic cleft as well as the presynaptic terminal and post synaptic receptor site

Synaptic transmission

how signals between neurons are transmitted chemically

what happens when the electrical impulse reaches the end of the neuron

the end of the neuron is called the presynaptic terminal, it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles

neurotransmitters

chemicals that diffuse across the synapse to the next neuron in the chain, they are taken up by the postsynaptic receptor sites and are then converted back into an electrical impulse

- each has its own specific molecular structure that fits perfectly into a post-synaptic receptor site

- has a specialist function

inhibition

decreases the likelihood that the neuron will fire

excitation

increases the neurons positive charge and making it more likely to fire

Localisation versus holistic theory

- Paul Broca and Karl Wernicke discovered that specific areas of the brain are associated with particular physical and psychological functions

- scientists believed that all parts of the brain were involved in the processing of thoughts and action

Localisation of function in the brain

The idea that different parts of the brain perform different tasks and are involved with different parts of the body, if a certain area of the brain becomes damaged the function associated with that area will also be affected

hemispheres of the brain

the brain is divided into two symmetrical halves called the left and right hemispheres

activity on the left-hand side of the body is controlled by the right hemisphere and vice versa

The cerebral cortex

the outer layer of both hemispheres, about 3mm thick and is what separates us from other animals as it it more developed

- appears grey due to the location of cell bodies

the sub-divisions of the cortex of the brain

named after the bones beneath which they lie; the frontal lobe, the pariental lobe, the occipital lobe and the temporal lobe

the motor area

located in the back of the frontal lobe, controls voluntary movement in the opposite side of the body and damage results in a loss of control over fine movements

the somatosensory area

located in the front of the pariental lobe, a valley separates the frontal lobe and pariental lobe called the central sulcus

it is where sensory information is represented (from the skin)

visual area

located in the occipital lobe, works in opposite to the eye

auditory area

located in the temporal lobe, analyses speech based information, damage may produce partial hearing loss

Broca's area

responsible for speech production, damage causes Broca's aphasia which is characterised by speech that is slow, laborious and lacking in fluency

Wernicke's area

responsible for language comprehension, damage leads to Wernicke's aphasia, often producing nonsense words (neologisms)

Brain scan evidence of localisation - Peterson et al

used brain scans to demonstrate how Wernicke's area was active during a listening task and that Broca's area was active during a reading task, shows different areas have different functions

Brain scan evidence of localisation - Tulving et al

long-term study revealed that semantic and episodic memories reside in different parts of the prefrontal cortex

Now a number of highly sophisticated and objective methods for measuring activity in the brain provide sound scientific evidence

Neurosurgical evidence of localisation - Dougherty et al

The practice of surgically removing and destroying areas of the brain to control aspects of behaviour, discovered in 1950s

44 OCD patients undergone angulotomy, after 32 weeks 1/3 met criteria for successful response - shows that symptoms and behaviours are localised

Lobotomy

A brutal and imprecise method of neurosurgery, only used in extreme cases of OCD and depression

Lashley's research to disprove localisation

suggests that higher cognitive functions, such as the process of learning are not localised but distributed in a more holistic way in the brain

Karl removed areas of the cortex in rats that were learning a maze, no area was proven to be more important than any other area

The process of learning appeared to require every part of the cortex; learning is too complex to be localised and requires involvement of the whole brain

Plasticity and localisation

when the brain has become damaged the appears able to reorganise itself in an attempt to recover the lost function, known as the law of equipotentiality, stroke victims are able to recover those abilities that were seemingly lost as a result of the illness

Brain plasticity

The brain has the ability change throughout life;

during infancy, the brain experiences a rapid growth in the number of synaptic connections it has, peaking at approximately 15,000 at age 2-3 years

More and more research suggests that at any time in life existing neural connections can change or form

synaptic pruning

as we age, rarely used connections are deleted and frequently used connections are strengthened

what was originally thought about brain plasticity

changes such as synaptic pruning were restricted to the developing brain within childhood and the adult brain would remain fixed and static in terms of function and structure

Research into plasticity - Eleanor Maguire et al

studied the brains of London taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than in a matched control group - this part of the brain is associated with the development of spatial and navigational skills in humans and other animals

- London cabbies must take a complex test called 'the knowledge' which assesses their recall of the city streets, the longer they had been in the job, the more pronounced was the structural differences (positive correlation)

Research into plasticity - Dragonski et al

Imaged the brains of medical students before and after final exams, learning-induced changes were seen to have occurred in the posterior hippocampus and the pariental cortex presumably as a result of the exam

Functional recovery after trauma

Unaffected areas of the brain are able to adapt and compensate for those areas that are damaged

it is an example of neural plasticity

healthy brain areas may take over

happens quickly after trauma - spontaneous recovery

what happens in the brain during recovery?

secondary neural pathways that would not typically be used to carry out certain functions are activated or unmasked to enable functioning to continue

- axonal sprouting

- reformation of blood vessels

- recruitment of homologous areas

axonal sprouting

the growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways

Practical application of plasticity and functional recovery

Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation

Physical therapy may be required to maintain improvements in functioning

Although the brain may have the capacity to fix itself to a point, this process requires further intervention if it is to be completed successfully

Negative plasticity

The brains ability to rewire itself can sometimes have maladaptive behavioural consequences, prolonged drug use for example has been shown to result in poorer cognitive functioning as well as an increased risk of dementia later in life

60-80% of amputees have been known to develop phantom limb syndrome- the continued experience of sensations in the missing limb as if it were still there, usually unpleasant- thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss

Age and plasticity

Functional plasticity tends to reduce with age, the brain has greater prosperity for reorganisation in childhood as it is constantly adapting to new experiences and learning

Age and plasticity - Ladina Bezzola et al

Demonstrated how 40 hours of golf training produced changes in the neural representation of movement in participants aged 40-60, using fMRI the researchers observed reduced motor cortex activity in the novice golfers compared to a control group - more effective neural representations after training

Neural plasticity does continue throughout lifespan

Animal studies - plasticity and functional recovery

David Huber and Turton Wiesel involves sewing one eye of a kitten shut and analysing the brains cortical responses, it was found that the area of the visual cortex associated with he shut eye was not idle (as had been predicted) but continued to process information from the open eye

Hemispheric lateralisation

The ability to produce and understand language is controlled by the left hemisphere

language is subject to this

It has been investigated through a series of ingenious experiments conducted by Roger Sperry and his colleagues

Roger Sperry

Awarded the novel prize in 1981 due to his split-brain research

Split-brain studies

Involved a unique group of individuals, all whom had undergone the same surgical procedures, the separation of the two hemispheres

The communication line between the two hemispheres was removed

This allowed Sperry to seethe extent to which the two hemispheres were specialised for certain functions and whether the hemispheres performed tasks independently of one another

Commissurotomy

The corpus callosum and other tissues which connect the two hemispheres are cut down the middle in order to separate the two hemispheres and control frequent epileptic seizures

Procedure of split brain research into hemispheric lateralisation

1. An image or word could be projected to the patients visual field and then processed by the opposite side of the brain

- in the normal brain, the corpus callosum would immediately share the information between both hemispheres

- presenting the image to one hemisphere of a split brain patient meant that the information could not be conveyed from that hemisphere to the other

Key findings of split brain research - describing what you see

When a picture of an object was shown to a patients right visual field they could easily describe what was seen but not for the left visual field, the patient typically reported that the was nothing there

Lack of language centres in the right hemisphere

Key findings of split brain research - recognition by touch

Patients are able to select a matching object from a grab bag of different objects using their left hand, was also able to select an object that was most closely associated with an object presented to the left visual field but could not verbally identify just understood what the object was

Key findings of split brain research - composite words

For example, 'key' on the left and 'ring' on the right, the patient would write with their left hand the word 'key' and say the word 'ring'

Key findings of split brain research - matching faces

The right hemisphere appeared dominant, the picture consistently selected when shown to the left visual field, the left hemisphere dominated in terms of verbal description but right in selecting matching pictures

split-brain research - demonstrated lateralised brain functions

Sperry's work has produced an impressive and sizable body of research findings, the left hemisphere is more geared towards analytical and verbal tasks whilst the right is more adept at performing spatial tasks and music, contributes to emotional and holistic content to language

Research suggests that the left hemisphere is the analyser whilst the right is the synthesiser

- a key contribution to our understanding of brain processes

split-brain research - strengths of the methodology

- experiments made use of highly specialised and standardised procedures

- typically, participants would be asked to stare at a given point, the 'fixation point'

- the image projected would be flashed up for 1/10 of a second, meaning the split-brain patient would not have time to move their eyes across the image and so spread the information across both sides of the visual field

- this allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving information at a time

= a very useful and well-controlled procedure

split-brain research - theoretical basis

Sperry's work prompted a theoretical and philosophical debate about the degree of communication between the two hemispheres in everyday functioning and the nature of consciousness

other researchers argued that the two hemispheres form a highly integrated system and are both involved in everyday tasks

split-brain research - theoretical basis, Roland Pucetti

have suggested that the two hemispheres are so functionally different that they represent a form of duality in the brain - we are all two minds but emphasised in split-brain

split-brain research - issues with generalisation

many researchers have urged caution in their widespread acceptance, as split-brain patients constitute such an unusual sample of people - there were only 11 who took part in all variations of the basic procedure, all of whom had a history of epileptic seizures, this may have caused unique changes in the brain that have influenced the findings

the control group, made up of 11 people with no history of epilepsy may have been inappropriate

functional magnetic resonance imaging (fMRI)

works by detecting the changes in blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain

when a brain area is more active it consumes more oxygen and to meet this increased demand, blood flow is directed to the active are (known as the haemodynamic response)

produces 3D images (activation maps)

showing which parts of the brain are involved in a particular mental process and this has important implications for our understanding of localisation of function

Electroencephalogram (EEG)

measures electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap

the scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity

often used by clinicians as a diagnostic tool as an unusual arrhythmic pattern of activity may indicate neurological abnormalities such as sleep disorders, epilepsy and tumors

Event-related potentials (ERPs)

using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out leaving only those responses that relate to the presentation of a specific task

what remains are event-related potentials: types of brainwave that are triggered by particular events

research as revealed many different forms of ERP and how, e.g., these are linked to cognitive processes such as attention and perception

Post-mortem examinations

a technique involving the analysis of a person's brain following their death

individuals whose brains are subject to this are likely to be those who have deficits in mental processes or behaviour during their lifetime

areas of damage within the brain are examined after death as a means of establishing a likely cause, it may involve comparison with a neurotypical brain

strengths of fMRI

- unlike other scanning techniques such as PET, it does not rely on the use of radiation. If used correctly it is virtually risk-free, non-invasive and straightforward to use

- produces images that have very high spatial resolution, depicting detail by the mm and providing a clear picture of how brain activity is localised

weaknesses of fMRI

- expensive compared to other neuroimaging techniques and can only capture a clear image if the person stays perfectly still

- it has poor temporal resolution - around 5 seconds time-lag behind the image on screen and the initial firing of neuronal activity

- can only measure blood flow - difficult to tell what kind of brain activity is being represented on screen

strengths of EEG

- proved essential in the diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of energy that can only be detected on screen

- contributed to understanding of stages involved in sleep (ultradian rhythms)

- extremely high temporal resolution, can accurately detect brain activity at a resolution of a single millisecond

weaknesses of EEG

- generalised nature of the information received

- the EEG signal is not useful for pinpointing the exact source of neural activity, and does not allow researchers to distinguish between activities originating in different but adjacent locations

strengths of ERPs

- bring much more specificity to the measurement of neural processes

- excellent temporal resolution - widespread use in the measurement of cognitive functions and deficits

- researchers have been able to identify many different types of ERP and describe the precise role of these in cognitive functioning

weaknesses of ERPs

- lack of standardisation in methodology between different research studies - makes it difficult to confirm findings

- in order to establish pure date in ERP studies, background noise and extraneous material must be completely eliminated, and this may not always be easy to achieve

strengths of post-mortem examinations

- post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain

- Paul Broca and Karl Wernicke both relied on PME in establishing links between language, brain and behaviour, decades before neuroimaging even became a possibility

weaknesses of post-mortem examinations

- causation, observable damage to the brain may not be linked to the deficits under review but some other unrelated trauma or decay

- ethical issues, consent from the patient before death, patients may not be able to provide informed consent, e.g. HM who lost his ability to form memories and was not able to provide such consent, post-mortem studies have been conducted on his brain still

Biological rhythms

That all living organisms are subject to which exert an important influence on the way in which body systems behave

governed by two things:

- the body's internal biological clocks which are called endogenous pacemakers

- external changes in the environment called exogenous zeitgebers

Circadian rhythms

a type of biological rhythm subject to a 24-hour cycle, which regulates a number of body processes such as the sleep/wake cycle and changes in core body temperature

the sleep/wake cycle

the fact we feel drowsy at night time and alert during the day demonstrates the effect of daylight, an important exogenous zeitgeber

free running

if our biological clock was left to its own devices without the influences of external stimuli such as light

Siffre's cave study

Michael, deprived of exposure to natural light and sound, but with access to adequate food and drink, spent 2 months in the caves of the Southern Alps

- in each case, his 'free running' biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours) though he did continue to fall asleep and wake up on a regular schedule

Jurgen Ashcoff and Rutger Wever study - circadian rhythms

convinced a group of participants to spend 4 weeks in a WWII bunker deprived of natural light, all but one displayed a circadian rhythm between 24 and 24 hours, the natural sleep/wake cycle may be slightly longer than 24 hours but it is entrained by exogenous zeitgebers such as the number of daylight hours and typical meal-times

- should not overestimate the influence of environmental cues on our internal biological clock

Simon Folkard et al study - circadian rhythms

studied 12 people who agreed to live in a dark cave for 3 weeks, sleep at 11:45pm and rising at 7:45am looking at a clock, the researchers gradually sped up the clock to be a 22 hour day instead - only one participant was able to adjust to the new regime

- shows we have a strong free running circadian rhythm

circadian rhythms - practical application to shift work

knowledge of circadian rhythms has given researchers a better understanding of the adverse consequences that can occur as a result of their disruption (known as desynchronisation)

- night workers experience a period of reduced concentration around 6 in the morning (a circadian trough) meaning mistakes and accidents are more likely

- significant relationship between shift work and poor health, shift workers 3x more likely t develop heart disease which may occur due to the stress of adjusting to different sleep/wake patterns and poor quality sleep during the day

= research into the sleep/wake cycle may have economic implications in terms of how best to manage worker productivity

circadian rhythms - practical application to drug treatments

circadian rhythms also coordinate a number of the body's basic processes such as heart rate, digestion and hormone levels - an effect on pharmacokinetics, the action of drugs in the body and how well they are absorbed and distributed

- there are certain peak times during the day/night that drugs are likely to be at their most effective

- also with the development of guidelines to do with the timing of drug dosing for a whole range of medications including anti-cancer, cardiovascular, respiratory etc.

circadian rhythms - use of case studies and small samples

- studies of the sleep/wake cycle tend to involve small groups of participants

- people involved may not be representative of the wider population and limits the extent to which meaningful generalisations can be made

- Siffre observed at the age of 60 his internal clock ticked much more slowly than when he was a young man

= even when the same person is involved, there are factors that vary which may prevent general conclusions being drawn

circadian rhythms - individual differences

individual cycles may vary, therefore generalisations can't be made

Duffy et al - some people display a natura; preference for going to bed early (known as 'larks') whereas some people prefer to do the opposite ('owls')

there are also age differences in sleep/wake patterns

Infradian rhythms

Takes longer than a day to complete

- the menstrual cycle is an example, it is governed by monthly changes in hormone levels which regulate ovulation - refers to the time between the first day of a woman's period to the day before her next period

- the typical cycle takes approximately 28 days to complete

- rising levels of hormone oestrogen cause the ovary to develop an egg and release it (ovulation)

- after ovulation the hormone progesterone helps the womb lining to grow thicker

- if pregnancy does not occur, the egg is absorbed into the body, the womb lining comes away and leaves the body (the menstrual flow)

Research study - the menstrual cycle, an infradian rhythm

although it is an endogenous system, evidence suggests that it may be influenced by exogenous factors, such as the cycles of other women

- Kathleen Stem and Martha McClinton, menstrual cycles may synchronise as a result of the influence of female pheromones - 29 women with a history of irregular periods, samples of pheromones were gathered from the armpit via cotton pad placed in their armpit, the pads were then treated with alcohol and frozen, to be rubbed on the upper lips of the other women - a different pad for each day of their cycle

- 68% of the women experienced changes to their cycle which brought them closer to the cycle of their 'odour donor'

Seasonal affective disorder (SAD)

- a depressive disorder which has a seasonal pattern of onset, classified as a mental disorder using DSM-5

- referred to as the winter blues as symptoms are triggered during winter months, daylight hours are shorter

- a circannual rhythm - subject to a yearly cycle

- can be a circadian rhythm as it may be caused by a disruption of sleep/wake cycle

- the hormone melatonin is implicated in the cause, during the night the pineal gland secretes melatonin until dawn when there's an increase in light - during the winter months a lack of light means the secretion process continues, its thought to have a knock-on effect on the production of seratonin in the brain which cause the depressive symptoms