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 two 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 two 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. What happens in the body when a stressor is perceived?

• the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system, triggering a stress response.

2. What change occurs in the ANS during a stress response?

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

3. What role does adrenaline play in the stress response?

• 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. What happens after a stressor 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, 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

The 3 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

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

Lateralisation

• these two hemispheres are lateralised meaning that some functions are mainly controlled by just one side.

• 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
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 understanding

• damage leads to Wernicke's aphasia, often producing nonsense words (neologisms)

Strength of localisation of function in the brain - case study evidence

• An individual known as Phineas gage had an incident while at work which led to an iron rod shooting through his head, taking part of his frontal lobe with it.

• This led to his personality supposably changing, making his less angry than he previously was.

• While this increases validity, it must be remembered that due to this only being the experience of one individual it cannot be generalised.

• This means that meaningful conclusions about localisation of function cannot be made.

Strength of localisation of function in the brain - Brain scan evidence + research support - Peterson and Tulving

• 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

• Also a study by Tulving revealed semantic and episodic memories are located in different areas of the prefrontal cortex.

• Therefore, validity is increased as a number of objective methods are used to provide valid scientific evidence.

Weakness of localisation of function in the brain - contradicting research

• research from advanced techniques, like FMRI, have indicated that regions in the RH and thalamus have also shown signs of language centres.

• Therefore, this suggests that a more holistic approach may actually be more valid than locationsation theory. 

Hemispheric lateralisation

• the theory that there are two halves of the brain that are functionally different.

• One example of this is all the language centres in humans being in the left hemisphere.

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

Briefly explain split brain research

• a series of ongoing studies involving individuals with epilepsy

• who had surgery separating the two hemispheres to reduce the severity of their fits

• now allows researchers to test lateral functions of the brain in isolation.

• This is due to the fact that the two hemispheres can no longer communicate.

Split brain research procedure - Sperry

• looked at 11 subjects who had split brains.

• He projected either an image or word to their right visual field (that is processed by the left hemisphere) and projected the same or a different image to the left visual field.

Sperry’s findigs

• When a picture was shown to the split brain patients right visual field they could explain what they were just shown, however when shown to their LVF they said they saw nothing which is due to the fact that the RH has no language centres.

• In a normal brain, the info would immediately be shared between the two hemispheres, giving a complete picture.

• However, the split brain patient was able to pick up an object that matched the image shown to their LVF with their left hand due to it being linked to the right hemisphere.

• Therefore this research shows that certain functions are lateralised and that the LH is verbal.

Strength of hemispheric lateralisation - greater insights into the brain

• it has provided greater insight into the functions of the brain.

• It supports and shows how the left hemisphere is important in language functioning, due to it containing all the language centres in the brain like the Broca's area and Wernicke's area.

• Therefore this overall supports the theory of lateralisation. 

Strength of hemispheric lateralisation - standardised procedure

• Sperry ensured that the picture or word was only shown for 1/10th of a second to the visual field in order to be sure that the other would not have time to also process it.

• The other eye was also blindfolded. T

• his means that the research is replicable and valid conclusions can therefore be drawn.

• This increases the validity of the theory. 

Weakness of hemispheric lateralisation - cannot be generalised

• The research Sperry has carried out relied on a poor sample as well as having no control group.

• The 11 split brain patients, which is already a very small sample, may have some unique changes in their brains due to their condition.

• The group also varied in ages and how severed their brains were, bringing up issues of comparability too.

• Therefore we cannot rely on this research alone to draw valid conclusions on lateralisation. 

Brain plasticity

• the brain's tendency to change and adapt as a result of experience and new learning.

• During infancy rapid growth of synaptic connections occurs and peaks at around the ages 2-3 years, this is twice as many as the adult brain

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 - Maguire

• studied the brains of london taxi drivers, finding that they had significantly more grey matter in the posterior hippocampus compared to a control group.

• This part of the brain is associated with the development of spatial and navigational skills

• She also found that the longer theyd been a taxi driver, the more pronounced the structural difference.

Functional recovery

• a form of plasticity and is the brain's ability to transfer/ redistribute functions following damage through trauma.

• Following physical injury, or other forms of trauma ie a stroke, unaffected areas of the brain are often able to adapt and compensate.

Spontaneous recovery

• Functional recovery can occur quickly (spontaneous recovery) and then slow down after a few weeks/ months and at this point the individual may then require therapy.

what happens in the brain during recovery?

• During this recovery the brain reorganises itself by forming new synaptic connections close to the area of damage which is supported by a number of structural changes.

• These include axonal sprouting, denervation supersensitivity and the recruitment of the homologous. 

axonal sprouting

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

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

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

Strength of research into plasticity - doesn’t always decline sharply with age (Bezzola)

• Bezzola demonstrated how 40 hours of golf training produced changes in the neural representations on participants aged 40-60.

• The researcher used an FMRI to observe activity in the brain and compared novice golfers to a control group.

• Results showed that the brain showed greater efficiency after training, suggesting that plasticity can continue into old age.

A strength of research into functional recovery - real world applications

• The understanding of processes involved in plasticity has contributed to neurohabilitation, which is the process of helping people recover after brain trauma.

• For example, it shows how axonal growth encourages new therapies to be tried.

• Therefore research has had positive implications.

Weakness of research into function recovery - cannot be generalised (Schneider)

• it cannot necessarily be generalised due to the level of education influencing recovery rates.

• Schneider found the more time spent in education, the greater the chances of a disability free recovery after brain trauma.

• The study found that 40% of patients that had achieved a DFR had over 16 years of education.

• Therefore this is a crucial factor that must be taken into account when looking at the level of recovery that can be achieved. 

Scanning techniques as a way of studying the brain - four main ways

• Researchers usually study the brain to investigate localisation - to determine which parts of the brain do what.

• There are four main ways of studying the brain using scanning techniques, including FMRI, EEGs, ERPs and post mortem examinations.

functional magnetic resonance imaging (fMRI)

• measures brain activity while the participant is doing a task

• creates a 3D image that highlights which part of the brain is active.

• It detects these changes by looking at changes in blood oxygenation and flow which changes in the area that's active.

Electroencephalogram (EEG)

• measure electrical activity via electrodes using a skull cap.

• This scan records brainwave patterns, showing overall activity which is generated through thousands of neurons.

• It is often used as a diagnostic tool for conditions such as epilepsy

Event-related potentials (ERPs)

• uses info from EEG’s and then a statistical averaging technique is used to filter out all extraneous brain activity and leaves just brain waves that are triggered by particular events instead of just showing overall brain activity.

• Therefore responses relating to the presentation of a specific stimulus or performance of a specific task is left

• for example a cognitive process like attention.

Post-mortem examinations

• where the brain is analysed following one's death.

• They are usually examined to establish the likely cause of a deficit or disorder the person had experienced.

Strengths of FRMI - no radiation and high resolution

• Doesnt rely on the use of radiation and is safe

• produces high resolution, showing detail by the millimetre

Weaknesses of FMRI - expensive and low temporal resolution

• they are expensive in comparison to other scanning techniques.

• As well as this they have low temporal resolution meaning that there is a 5 second lag between activity and this showing up on the image, this will make it harder to draw accurate conclusions due to cause and effect being harder to establish. 

Strengths of EEG - practical aplications and high temporal resolution

• they have contributed to our understanding of sleep stages, therefore having practical applications.

• Moreover, they also have high temporal resolution, showing brain activity within one millisecond of it occurring, making it easier to establish cause and effect more accurately.

Weaknesses of EEG’s - generalised

• produces a generalised signal from thousands of neurons, so difficult to know the exact source of neural activity

Strengths of ERPs - specific and high temporal resolution

• measures of neural processes more specific than EEG

• good temporal resolution (better than FRMI)

Weaknesses of ERPs - not standardised + hard to achieve

• lack of standardisation so difficult to confirm findings

• in order to gain data all ‘background noise’ must be removed which isn’t easy to achieve

Strengths of post-mortem examinations - practical applications

• Broca and Wernicke both relied on these before newer techniques were discovered

• can examine deep areas

• therefore has practical applications

Weaknesses of post-mortem examinations - unrelated trauma and ethical issues

• any observed damage may be related to other unrelated trauma, and not relating to whatever deficit they were experiencing/ what's being investigated.

• This reduces the validity.

• Additionally, this technique has ethical issues due to no consent being obtained, raising debates on morality. 

Biological rhythms

• distinct patterns of changes in body activity that conform to cyclical time periods and are governed by two things;

• external biological clocks 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

• Endogenous pacemakers provide info from the eye about light, governed by the super charismatic nucleus.

• Exogenous zeitgebers result in us feeling drowsy when it's night time, and alert in the day, showing the effects of daylight

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

• spent several extended periods underground in a cave in order to study the effects of this on biological rhythms.

• He found that his ‘free running’ rhythm settled down to 25 hours, just beyond the usual 24, showing he continued to fall asleep and wake up on a regular schedule.

• this is because EZ’s can also reset the SCN.

Research into circadian rhythms - Anschoff

• Anschoff got a group to stay in a WW2 bunker for 4 weeks, finding a rhythm of 24-25 hours, with the exception of one whose was 29.

• He found that it may be slightly longer but it is entrained by EZ’s associated with our 24 hour day, like meal times and daylight hours.

Research into circadian rhythms - Folkward

• Folkward studied a group of 12 who lived in a dark cave for 3 weeks going to bed when the clock said 11:45pm and waking up when it said 7:45am.

• The researchers then gradually sped up the clock to create a 22 hour day, with the participants being unaware of this.

• Only one participant comfortably adjusted, suggesting the existence of a free running circadian rhythm that is not controlled by EZ’s. 

strength of research into circadian rhythms - practical applications

• Shift work creates desynchronisation of biological rhythms and researchers have found that workers will experience a lapse of concentration at around 6 am, known as a circadian trough.

• This lapse means that accidents are more likely to happen and there is also a link between shift work and poor health as its been found that they are three times more likely to develop heart disease.

• Therefore furthers our understanding, allowing systems like this to have a much needed improvement

strength of research into circadian rhythms - real world aplications

• real world applications to medical treatments.

• Circadian rhythms coordinate basic processes like heart rate and hormone levels. T

• hese rise and fall multiple times throughout the day which has then led to the production of chronotherapeutics which are administered in a way that corresponds to a person's biological rhythms.

• An example of this is aspirin being much more effective at reducing heart attacks when taken at night.

• Therefore research has helped to increase the effectiveness of drugs like this.

weakness of research into circadian rhythms - cannot be generalised

• This is due to the research only being conducted on small groups or individuals, meaning that individual differences are likely to impact any results.

• For example, Siffre did a second experiment when he was much older, at the age of 60, and found that his internal clock was much slower than when he conducted the experiment at a younger age.

• Therefore, it will be harder to draw accurate conclusions.

Infradian rhythms

• a type of a biological rhythm, having a frequency of less than one cycle in 24 hours.

 the menstrual cycle

• lasts on average around 28 days.

• During each cycle, rising levels of the hormone oestrogen causes the ovary to develop an egg and release it.

• Next, progesterone helps the womb lining thicken, readying the womb for pregnancy.

• However, if pregnancy doesn't occur then the egg is absorbed and the lining breaks down which is known as the menstrual flow.

Research on the menstrual cycle

• Research has been done on 29 women with irregular periods suggesting that EZ’s may synchronise the menstrual cycle (the cycles of other women).

• Firstly, pheromones were taken from some of the women when at different stages of their cycles via a cotton pad under their armpits.

• These pads were then cleaned with alcohol and rubbed on the upper lips of other participants.

• It was found that 68% of women experienced changes in their cycle which brought them closer to the cycle of the ‘odour donor’.

Seasonal affective disorder (SAD)

• This is said to be caused by the hormone melatonin as in winter due to there being less light, more secretion takes place which then has a knock on effect of the production of serotonin in the brain (happy hormone)

Ultradian rhythms

• has a frequency of more than one cycle in 24 hours

Sleep cycle and its 5 stages

• all together last around 90 minutes - this continues throughout the night.

• Each stage is characterised by a different level of brainwave activity.

• These stages include light sleep (1 and 2), deep sleep (3 and 4) and REM sleep (5).

strength of research into infradian rhythms - the evolutionary basis of the menstural cycle

• In previous years it may have been advantageous for females to be pregnant at the same time as if babies were to lose their mothers, they could still get breast milk from elsewhere in the social group, improving their chance of survival.

• Therefore has potential evolutionary support.

weakness of research into infradian rhythms - methodological issues

• Many factors may lead to a change in a woman's cycle, for example diet and stress, meaning that any change that occurred may have just been by chance.

• Moreover, no one has replicated the same results which suggests this is true.

• Therefore accurate conclusions cannot be drawn as the results are flawed.