Approaches in psychology Flashcards
(121 cards)
1
Q
What did Descartes suggest?
A
- Suggested that mind and body represented a dualism.
- They interact in different ways to produce different behaviours and thoughts.
2
Q
What did Wundt do?
A
- 1879, Wundt set up his first laboratory where he adopted the use of introspection.
- Wundt isolated conscious thoughts into basic structures of thoughts, processes and images, in a process called structuralism (very scientific).
3
Q
What is introspection?
A
A means of learning about one’s own currently ongoing mental states or processes.
4
Q
What is the behaviourist approach?
A
The behaviourist approach is a way of explaining behaviour in terms of what is observable and in terms of learning.
5
Q
Define classical conditioning?
A
Classical conditioning is learning by association. This occurs when two stimuli are repeatedly paired together - an unconditioned (unlearned) stimulus (UCS) and a new neutral stimulus. The neutral stimulus eventually produces the same response that was first produced by the unlearned response alone.
6
Q
Describe Pavlov’s example of classical conditioning.
A
1) Before conditioning:
–> food (unconditioned stimulus) - unconditioned response (salivation).
2) Before conditioning:
–> bell (neutral stimulus) - no conditioned response (no salivation).
3) During conditioning:
–> bell + food - unconditioned response (salivation).
4) After conditioning:
–> Bell conditioned stimulus - conditioned response (salivation).
7
Q
What did Pavlov show?
A
- Pavlov showed how a neutral stimulus (bell) can lead to a new learned response (conditioned response) through association.
- Found stimulus generalisation - dog salivated with change of type and pitch of bell (association made to the new stimulus).
- Cut off point of stimulus generalisation - when stimulus discrimination occurs.
- Found temporal contiguity - the association only occurs if unconditioned and neutral stimulus are presented at the same or around the same time as each other (if gap is too big, no association made).
8
Q
What is stimulus generalisation?
A
Stimulus generalisation is when a stimulus becomes generalised to other related stimuli which are also associated with the conditioned response.
9
Q
What is stimulus discrimination?
A
Stimulus discrimination is when a stimulus is not associated with the conditioned response as it is too different from the original stimulus.
10
Q
What is operant conditioning?
A
Operant conditioning is a form of learning in which behaviour is shaped and maintained by its consequences. Possible consequences include positive reinforcement, negative reinforcement and punishment.
11
Q
What is positive reinforcement?
A
Positive reinforcement is where a behaviour is more likely to reoccur because of positive consequences.
12
Q
What is negative reinforcement?
A
Negative reinforcement is where a behaviour is more likely to reoccur because of avoidance of negative consequences.
13
Q
What is punishment?
A
Punishment means a behaviour is less likely to reoccur because of the negative consequences.
14
Q
Describe Skinner’s views of operant conditioning.
A
- Skinner believed learning is an active process whereby humans operate on their environment.
- 3 types of consequences for behaviour in operant conditioning: positive reinforcement, negative reinforcement, and punishment.
- Positive and negative reinforcement increase the chance of a behaviour being repeated - where punishment decreases it.
15
Q
Describe how Skinner researched operant conditioning.
A
He put an animal in the Skinner Box where an animal pushes a lever and the box would deliver either a positive reinforcement (food) or a punishment/negative reinforcement (electric shock).
16
Q
What are the advantages of the behaviourist approach?
A
- The use of scientific methodology gave psychology credulity - highly controlled and replicable.
- Real life application - token economy systems (reward appropriate behaviour with tokens that can then be exchanged for rewards).
17
Q
What are the disadvantages of the behaviourist approach?
A
- Deterministic - assumes people are passive puppets of their circumstances, ignores free will.
- Ignore wider influences of cognitive processing.
- Ethical issues- harm to animals in Skinner box.
- Application of animal studies to humans.
- Support nurture (ignores impact of nature).
- Spotaneous behaviour is not easily explained by classical or operant conditioning.
18
Q
What were Bandura’s assumptions?
A
- Agreed that behaviour is learned from experience.
- SLT proposes a different way to learn - through observation and limitation of others within a social context (social learning).
- SLT suggests learning happens directly (through classical and operant conditioning) and indirectly.
Behaviour is learned from the environment, ignoring the genetic influence on behaviour. - Behaviour is learned from observing others and the reinforcement or punishment they receive.
19
Q
Explain vicarious reinforcement.
A
- For indirect learning to take place an individual observes the behaviour of others.
- Learner may imitate the behaviour but in general imitation only occurs if behaviour is seen to be rewarded (reinforced) rather than punished.
- In vicarious reinforcement, the learner observes the behaviour and the consequences of a behaviour.
20
Q
What is SLT?
A
SLT is often described as the ‘bridge’ between traditional learning theory (behaviourism) and the cognitive approach. This is because it focuses on how mental (cognitive) factors are involved in learning.
21
Q
Describe mediational processes
A
- SLT is the bridge between traditional learning theory (behaviourism) and the cognitive approach as it focuses on how mental factors are involved.
- The mental factors mediate (intervene) in the learning process to determine whether s new response is required.
22
Q
Explain the four meditational process Bandura identified (1977)
A
1) attention: the extent to which we notice certain behaviours.
2) retention: how well the behaviour is remembered.
3) motor reproduction: ability of the observer to perform the behaviour.
4) motivation: the will to perform the behaviour, which is often determined by whether the behaviour was rewarded or punished.
- Attention and retention relate to learning of behaviour.
- Motor reproduction and motivation relate to performance of behaviour.
- Unlike traditional behaviourism, learning and performance do not need to occur together.
- Observed behaviours may be stored by the observer and reproduced at a later time.
23
Q
Explain identification
A
- People (especially children) are more likely to imitate the behaviour of those they identify with - role models.
- Process is called modelling.
- A person becomes a role model if they possess similar characteristics to the observer and/or are physically attractive and have high status.
- Role models do not have to be physically present - implications from the media.
24
Q
What are the advantages of the SLT?
A
- Neither classical conditioning nor operate conditioning can account for learning on their own - SLT offers a more comprehensive explanation by accounting for meditational processes.
- SLT can explain cultural differences in behaviour - differences are due to different observational contexts.
- Bandura emphasised reciprocal determinism (not merely influenced by the environment but also exerts an influence upon it) - suggests some free will in behaviour.
- Applicable - video nasties impact on children.
- SLT can explain the initiation of behaviours.
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What are the disadvantages of SLT
- Over reliance on laboratory experiments - the children may have suffered from demand characteristics (acting differently due to the researcher presence).
- Ignores biological factors - there were gender difference that cannot be accounted for by SLT in the aggression shown towards the Bobo doll (boys found to be more aggressive than girls).
- Cumberbatch (2001) - disputes the link between media and real life violence.
- SLT cannot explain behaviour where there is no apparent role model.
26
What is the cognitive approach?
The cognitive approach uses experimental research methods to study internal mental processes such as attention, perception, memory and decision-making.
27
What is the information-processing model?
Input (comes from the environment via the sense and is encoded but the individual) —> processing (information one encoded can be processed - such as processing of schemas) —>output (behavioural response, emitted following processing).
28
What are the assumptions made within the cognitive approach?
- Thought processes can and should be scientifically studied - inspection is too unscientific and well controlled laboratory studies can investigate thinking.
- Can investigate areas neglected by behaviourists such as memory, perception and thinking.
- Cognitive psychologists study these ‘private’ processes indirectly by making inferences about what is going on in the mind.
- The mind works like a computer in that it has input from ours senses which then processes and produces an output such as language or specific behaviours.
- Stimulus and response is appropriate but only if the thought processes that occur between stimulus and response are acknowledged (direct criticism of behaviourism).
29
What are theoretical and computer models?
- Studies internal processes through theoretical models - information processing approach (input -> storage -> retrieval).
- Uses computer models, ‘computer analogy’ suggesting there are similarities in processing.
- Models includes concept of cerebral processing unit (brain), coding (turn information into usable format), and the use of stores (hold information).
30
Describe the role of schema.
- Schemas are frameworks of ideas and information developed through experience.
- Aid in interpretation of incoming information received by the cognitive system.
- Babies born with simple motor schema (become more sophisticated with age).
- Mental shortcut, can process lots of info quickly..
- May lead to errors in perception.
- Means we all see own version of reality - unique, same culture similar schema.
- Important role in memory formation.
31
Explain the emergence of cognitive neuroscience.
- Cognitive neuroscience is the study of specific brain structure on mental processes.
- Broca’s area - damage to frontal lobe can damage speech.
- Brain scanning techniques (PET & fMRI) lead to further discovery of mental processes.
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What are the advantages of the cognitive approach.
- Focus of cognitive approach is the importance of thought processes: have great influence on behaviour.
- Uses scientific methodology: laboratory experiments have scientific rigour.
- Application: treatment of depression CBT.
- Application: advancing field of AI.
- Less deterministic than other approaches: focus on soft determinism (recognises cognitive system can only operate within the limits of what we know).
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What are the disadvantages of the cognitive approach.
- Lacks validity: artificial tasks/environment of laboratory experiments.
- Use of models oversimplifies complex mental processes: ignores role of emotion.
- Mechanistic: compares people to computers, ignores free will.
34
What is the psychodynamic approach?
A perspective that describes the different forces (dynamics) most of which are unconscious that operate on the mind and direct human behaviour and experience.
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What are the assumptions of the psychodynamic approach?
- Unconscious mind: driving force behind behaviour.
- Instincts/drive: motivate our behaviour (Libido - life instinct, Thanatos - death instinct).
- Early childhood experiences: key role in shaping later development.
36
What is the role of the unconscious?
- Freud suggested the part of the mind that we know about and are aware of is the conscious mind - the 'tip of the iceberg'.
- Most of the mind is made up of the unconscious.
- Unconscious - part of the mind that we are unaware of but continues to direct much of our behaviour, vast storehouse of biological drives and instincts that has a significant influence on behaviour and personality.
- Unconscious can contain threatening and disturbing memories that have been repressed, these can be accessed during dreams or through parapraxis.
- Just below the surface of the unconscious mind is the preconscious which contains thought and memories which are not currently in conscious awareness but we can access if desired.
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What is the id?
Entirely unconscious, the id is made up of selfish aggressive instincts that demand immediate gratification.
38
What are the features of the id?
- primitive part of the personality.
- operates on the pleasure principle.
- mass of unconscious drives and instincts.
- only the id is present at birth.
39
What is the ego?
The reality check that balances the conflicting demands of the id and the superego.
40
What are the features of the ego?
- Works on the reality principle.
- Mediator between the other two parts of the personality.
- Ego develops around 2 years and role is to reduce conflict between the demands of the id and superego (this can be done through defence mechanisms).
41
What is the superego?
The moralistic part of the personality which represents the ideal self, how we ought to be.
42
What are the features of the superego>
- Formed at the end of the phallic stage, around age of 5.
- Internalised sense of right and wrong.
- Based on morality principle, represents the moral standards of the child's same sex parent and punishes the ego for wrongdoing (through guilt).
43
What are the psychosexual stages (as a whole)?
5 developmental stages that all children pass through, at each stage there is a different conflict the outcome of which determines future development.
- Any psychosexual conflict that is unresolved leads to fixation, where the child becomes stuck and carries certain behaviours and conflicts associated with this stage through adult life.
44
When is the oral stage?
0-1 years.
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Describe the oral stage.
Focus of pleasure is the mouth, mother's breast is the object of desire.
46
What is the consequence of unresolved desire in the oral stage?
Oral fixation - smoking, biting nails, being sarcastic, critical.
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When is the anal stage?
1-3 years.
48
Describe the anal stage.
Focus of pleasure is the anus, child gains pleasure from withholding and expelling faeces.
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What is the consequence of unresolved conflict in the anal stage?
Anal retentive - perfectionist, obsessive.
Anal expulsive - thoughtless, messy.
50
When is the phallic stage?
3-5 years.
51
Describe the phallic stage.
Focus of pleasure is the genital area, child experiences the Oedipus or Electra complex.
52
What are the consequences of unresolved conflict in the phallic stage?
Phallic personality - narcissistic, reckless, possibly homosexual.
53
When is latency?
5-puberty.
54
Describe latency stage.
Earlier conflicts are repressed.
55
When is the genital stage?
Puberty
56
Describe the genital stage.
Sexual desires become unconscious alongside the onset of puberty.
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What are the consequences of unresolved conflict in the genital stage?
Difficulty forming heterosexual relationships.
58
What is the Oedipus complex?
In the phallic stage, little boys unconsciously develop incestuous feelings towards their mother and murderous feelings towards their father (their rival in love).
Fearing their father will castrate them, boys repress their feelings for their mother and identify with their father, taking on his gender role and moral values.
59
What is the Electra complex?
Girls of the same experience penis envy, they desire their father (as the penis is the primary love object) and hate their mother.
Girls give up their desire for their father over time and replace this with a desire for a baby (and so identifying with their mother).
60
What case supports the Oedipus complex and what happens?
Oedipus complex is supported by the case of Little Hans - Hans had a fear of horses which Freud suggested was displacement of the castration fear of his father (more likely because he saw a horse die in the street).
61
What is a defence mechanism?
Unconscious strategies that the ego uses to manage conflict between the id and the superego.
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What do defence mechanisms do?
- Ensures the ego is not overwhelmed by temporary threats or traumas.
- Often involve some distortion of reality and as la long term solution are regarded as unhealthy and undesirable.
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What is repression?
Forcing a distressing memory out of the conscious mind.
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What is denial?
Refusing to acknowledge some aspect of reality.
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What is displacement?
Transferring feelings from true source of distressing emotion onto a substitute target.
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What are the advantages of the psychodynamic approach?
- Explanatory power: Freud's theory has been hugely influential on psychology (a major force in the first half of the 20th century). Used to explain a wide range of phenomena including personality development, abnormal behaviour, moral development and gender. Significant in drawing attention to the impact of early childhood experience (ignored previously).
- Practical application: as part of the psychodynamic approach Freud introduced a new form of therapy - psychoanalysis. This lead the way for most of today's talking therapies. This is useful with mild symptoms of mental disorders.
67
What are the disadvantages of the psychodynamic approach?
- Case study method: Freud's theories based on intensive study of single individuals who were often in therapy (Little Hans). Though detailed and carefully recorded, not possible to make general theories form such a small sample. His interpretations were also very subjective, a different researcher wouldn't have viewed the same way. His methodology also lacks scientific rigour.
- Untestable concepts: Popper - psychodynamic approach does not meet the scientific criteria of falsificationism. Many of his concepts occur at an unconscious level, difficult to test. This approach is at best pseudoscience.
- Psychic determinism: Freud believed that in human behaviour there was no such thing as an accident. Everything is driven by unconscious forces and has deep symbolic meaning - means free will is simply an illusion.
68
What is the humanistic approach?
An approach to understanding behaviour that emphasises the importance of subjective experience and each person’s capacity for self-determination.
69
What are the basic assumptions of humanistic psychology?
- Every individual is unique.
- Free will.
- People should be viewed holistically.
- Scientific method is not appropriate to measure behaviour.
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What is free will?
- The notion that humans can make choices and are not determined by biological or external forces.
- Claims human beings are self-determining and have free will, they are active agents who have the ability to determine their own development.
- Person centred approach.
71
What is self-actualisation?
-The desire to grow psychologically and fulfil one’s full potential, becoming what you are capable of.
- Every person has an innate tendency to achieve their full potential.
72
What is a hierarchy of needs?
- A 5 levelled hierarchical sequence in which basic needs (such as hunger) must be satisfied before higher psychological needs (such as self-esteem and self-actualisation) can be achieved.
- First 4 levels must be met before self-actualisation.
- Personal growth is an essential part of being human and is concerned with developing and changing as a person to become fulfilled.
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What are the levels of Abraham Maslow’s hierarchy of needs?
Physiological, safety, belonging - love, self-esteem, self-actualisation.
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What is involved in the psychological level?
Food, water, shelter, warmth.
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What is involved in the safety level?
Security, stability, freedom from fear.
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What is involved in the belonging - love level?
Friends, family, spouse, lover.
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What is involved in the self-esteem level?
Achievement, mastery, recognition, respect.
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What is involved in the self-actualisation level?
Pursue inner talent, creativity and fulfilment.
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What is self?
Ideas and values that characterise ‘I’ and ‘me’ and includes perception and valuing of ‘what I am’ and ‘what I can do’.
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What is congruence?
- When the self-concept and ideal self broadly match.
- Rogers argued that for personal growth to be achieved, there needs to be congruence between the self and ideal self.
- Client centred therapy helps to address this.
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What are conditions of worth?
- When a parent place s limits or boundaries on their love of their children.
- Rogers therefore thought the role of an effective therapist was to provide his clients with the unconditional positive regard they did not receive as children.
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What is client centred therapy?
- Modern day psychotherapy.
- ‘Clients’ not ‘patients’, experts of their own condition.
- Not directive with therapeutic atmosphere.
- Rogers ‘ should provide’ - genuineness, empathy, and unconditional positive regard.
- Increase self-worth, reduce incongruence and help functioning in pursuit of self-actualisation.
- Major influence on counselling.
- Praised for focusing on present not dwelling on the past.
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What are the advantages of the humanistic approach?
- Not reductionist: human psychologist advocate holism (the idea that subjective experience can only be understood by considering the whole person, more valid approach by considering meaning human behaviour within a real life context.
- Positive approach: humanistic psychology has been praised for ‘bringing the person back into psychology and presenting a positive image of the human condition, optimistic approach that sees all people as basically good, free to work towards the achievement of their potential and in control of their lives, allows for personal development and growth of the individual - can change as a consequence of our environment.
84
What are disadvantages of the humanistic approach?
- Limited application: limited impact upon psychology as a whole, lacks a secure evidence base, rather than an approach it is considered as a loose set of abstract concepts.
- Untestable concepts: humanistic psychology does contain a number of vague ideas that are abstract and difficult to test, self-actualisation, free will and congruence are concepts that would be difficult to empirically measure, humanistic psychology is anti-scientific, individual subjective experience is difficult to test and quantify.
- Cultural bias: many of the ideas that are central to humanistic psychology, such as individual freedom, autonomy and personal growth are more closely associated with individualist cultures, collectivist cultural values do not fit as well with humanistic psychology.
85
What id the biological approach?
A perspective that emphasises the importance of physical processes in the body such as genetic inheritance and neural function.
86
What are some other aspects of the biological approach?
- Suggests that everything psychological is first biological.
- To fully understand human behaviour must look at biological structures and processes in the body such as genes, neurochemistry and the nervous system.
- From a biological perspective the mind lives in the brain - meaning all thoughts, feelings and Breda i our have a physical basis.
87
What are genes?
They make up chromosomes and consist of DNA which codes the physical features of an organism and psychological features. Genes are inherited.
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What are twins used for (genetic basis of behaviour)?
Twin studies are used to determine the likelihood that certain traits have a genetic basis by comparing the concordance rates between pairs of twins.
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What is the genotype?
The particular set of genes that a person possesses, their actual genetic make up.
The expression of the genotype is influenced by environmental factors meaning how they are expressed can differ (phenotype).
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What is the phenotype?
Characteristics of an individual determined by both genes and the environment, this is the way genes are expressed through physical, behavioural and psychological characteristics.
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What is evolution?
The changes in inherited characteristics in a biological population over successive generations.
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What is evolution based on?
Based on Darwin’s theory of natural selection - genetically determined behaviour that enhances survival will continue in following generations, selection occurs simply because some traits give the possessor certain advantages allowing them to reproduce and pass sown those genes.
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What are the advantages of the biological approach?
- Scientific methods of investigation: Biological approach uses a range of precise and highly scientific methods, advances in technology mean it is possible to accurately measure biological and neural processes in objective way (based on reliable data).
- Real life application: increased understanding of the brain has led to the development of psychoactive drugs (can treat things like depression).
- Casual conclusions: biological approach offers explanations for mental illness in terms of the action of neurotransmitters in the brain.
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What are the disadvantages of biological approach?
- Can be accused of reductionism.
- Determinist view of behaviour: biological approach is determinist in the sense that it sees human behaviour as governed by internal biological causes over which we have no control.
- Cannot separate nature and nurture: it is impossible to separate out genetic and environmental; influences on behaviour.
95
What is the nervous system?
Consists of central nervous system and peripheral nervous system.
- It is a specialised network of cells in the human body and the primary internal communication system.
- It is divided into 2 subsystems: CNS and PNS.
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What are the two main functions of the nervous system?
- Collect process and respond to information in the environment.
- To coordinate the workings of different organs and cells in the body.
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What is the CNS and what does it do?
- The central nervous system consists of the brain and spinal cord and is the origin of all complex commands and decisions.
- The brain is the centre of all conscious awareness; the cerebral cortex (brain’s outer layer) is highly developed in humans and is what distinguishes our higher mental functions from those of animals, the brain is divided into two hemispheres.
- Spinal cord is an extension of the brain and is responsible for reflex actions such ad pulling hand away from hot object.
- CNS passes messages to and from the brain and connects nerves to the PNS.
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What is the peripheral nervous system and what does it do?
- It send information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body.
- The PNS is further subdivided into the autonomic nervous system (ANS) and the somatic nervous system (SNS).
- ANS - transmits information to and from internal bodily organs, it is autonomic s the system operates involuntarily, it governs vital functions in the body such as breathing, heart rate, digestion, sextuplets arousal and stress responses, subdivided into the sympathetic and parasympathetic nervous system.
- SNS - transmits information from receptor cells in the sense organs to the CNS, it also receives information from the CNS that directs muscles to act, it controls muscle movement and receives information from sensory receptors.
99
What is the endocrine system and what does it do?
- The endocrine system is one of the body’s major information systems that instructs glands to release hormones directly into the bloodstream, form ones are then carried to target organs in the body.
- The endocrine system acts more slowly than the nervous system but had widespread and powerful effects.
- Various glands in the body produce hormones.
100
What are hormones?
Chemical substances that circulate in the bloodstream and affect target organs, they are produced in large quantities but disappear quickly.
E.g. thyroid gland produces hormone thyroxine, it increases heart rate and affects other cells in the body by increasing metabolic rates which in turn affects growth rates.
101
What is a pituitary gland?
Located in the brain and known as the ‘master gland’ as it controls the release of hormones from all other glands in the body.
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What id the function of the pituitary gland?
Some of the hormones released are important for regulating the endocrine system, hence the nickname master gland.
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What is the function of the adrenal gland?
Important part of fight or flight response as it facilitates the release of adrenaline.
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What is the function of the testes?
Facilitates the release of testosterone (male hormone).
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What is the function of the ovaries?
Facilitates the release of oestrogen and progesterone (female hormone).
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What id fight or flight?
- The way an animal responds when stressed, the body becomes physiologically aroused in readiness to fight an aggressor or in some cases flee.
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What does fight or flight include?
Involves coordination of both the ANS and the endocrine system.
The hypothalamus recognises there is a threat, and it sends a message to the adrenal gland (specifically the adrenal medulla) triggers the release of adrenaline to the endocrine and no adrenaline in the brain this prompts changes linked to activation of the sympathetic nervous system (such as increased heart rate and breathing).
108
What are the sympathetic and parasympathetic nervous systems?
- Parasympathetic branch of the ANS and the sympathetic branch work in opposition to each other, their actions are antagonistic.
- Parasympathetic system (sometimes known as the rest and digest system) acts as a brake and reducers the activities of the body that were incre`asked by the sympathetic nervous system.
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What does the sympathetic nervous system do?
- Increases heart rate.
- Increase breathing rate.
- Dilates pupils.
- Inhibits digestion.
- Inhibits saliva production.
- Contracts rectum.
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What does the parasympathetic nervous system do?
- Decreases heart rate.
- Decreases breathing rate.
- Constricts pupils.
- Stimulates digestion.
- Stimulates saliva production.
- Releases rectum.
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What is a neuron?
Basic building bocks of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals.
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What are the three main types of neuron?
- Sensory neurons: carry messages from the PNS to the CNS, they have long dendrites and short axons.
- Relay neurons: these connect sensory neurons to the motor and other relay neurons, they have short dendrites and short axons.
- Motor neurons: these connect the CNS to effectors such as muscles and glands, they have short dendrites and long axons.
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What is the structure of the neuron?
- Neurons vary in size, but they all share the same basic structure.
- The cell body includes the nucleus which has the genetic material of the cell.
- Branch like structures called dendrites protrude from the cell body and they carry nerve impulses from neighbouring neurons towards the cell body.
- The axon carries impulses away from the cell body down the length of the neuron.
- The axon is covered by a fatty layer of myelin sheath which protects the axon and speeds up electrical transmission of the impulse.
- The myelin sheath is segmented by gaps called the nodes of Ranvier, this speeds up transmission as the impulse jumps between the gaps.
- Finally at the end of the axon are terminal buttons that communicate with the next neuron across a gap known as the synapse.
114
Describe electrical transmission - the firing of a neuron.
- When a neuron is in a resting states the inside of the cell is negatively charged compared to the outside.
- When a neurons 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.
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How does chemical transmission work (synapses)?
- Neurons communicate weigh each other within groups known as neural networks.
- Each neuron is separated from the next by a synapse.
- The synapse includes the space between them (synaptic cleft) as well as the presynaptic terminal and postsynaptic receptor site.
- Signals within neurons are transmitted electrically.
- Signals between neurons are transmitted chemically by synaptic transmission.
- When an electrical impulse reaches the end of the neuron (the presynaptic terminal) it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles.
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What is a neurotransmitter?
Chemicals that diffuse across the synapse to the next neuron in a chain.
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How does a neurotransmitter work?
Once the neurotransmitter crosses the gap it is taken up by the postsynaptic receptor sites (dendrites of the next neuron).
- The chemical message is then converted back into an electrical impulse and the process of transmission begins again in this other neuron.
- Dozens of types of neurotransmitter have been identified in the brain.
- Each neurotransmitter has its own specific molecular structure that fits perfectly into a postsynaptic receptor site, similar to a lock and key.
- Neurotransmitters also have specialist functions e.g. acetylcholine is found at each point where a motor neuron meets a muscle and upon its release will cause muscles to contract.
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What effect must neurotransmitters have?
Neurotransmitters have either excitatory or inhibitory effects on neighbouring neurons.
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What is excitation?
When a neurotransmitter, such as adrenaline, increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse.
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What is inhibition?
When a neurotransmitter, such as serotonin, makes the charge of the postsynaptic neuron more negative. This decreases the likelihood that the neuron will fire and pass on the electrical impulse.
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What is summation?
- The question of whether a postsynaptic neuron does fire is decided by the process of summation.
- The excitatory and inhibitory influence are summed - if the net effect on the postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire, if the net effect is excitatory it is more likely to fire.
- The action potential of the postsynaptic neuron is only triggered if the sum of the excitatory and inhibitory signals at any one time reaches the threshold.
