PS16: Neurons & Synapses
How neurons communicate: the structure of neurons, electrical and chemical transmission, synaptic transmission, and the role of neurotransmitters including serotonin and dopamine.
Neurons & Synapses
How neurons communicate: the structure of neurons, electrical and chemical transmission, synaptic transmission, and the role of neurotransmitters including serotonin and dopamine.
Key Fact: Neurons are nerve cells that transmit electrical impulses. Three types: sensory neurons (carry signals from senses to CNS), relay neurons (connect sensory and motor neurons within the CNS), motor neurons (carry signals from CNS to muscles/glands).
Key Fact: Neuron structure: cell body (contains nucleus), dendrites (receive signals from other neurons), axon (long fibre carrying electrical impulses), myelin sheath (insulates axon, speeds up transmission), terminal buttons (release neurotransmitters at synapses).
Key Fact: Synaptic transmission: when an electrical impulse reaches the end of a neuron, it triggers release of neurotransmitters from vesicles in the terminal buttons. These cross the synaptic cleft and bind to receptors on the next neuron, triggering a new electrical impulse.
Key Fact: Neurotransmitters: excitatory neurotransmitters (e.g. glutamate, adrenaline) make the next neuron MORE likely to fire. Inhibitory neurotransmitters (e.g. GABA, serotonin) make the next neuron LESS likely to fire. The balance of excitatory and inhibitory signals determines whether a neuron fires.
Key Fact: Key neurotransmitters: serotonin (mood regulation - low levels linked to depression and aggression), dopamine (reward and motivation - involved in addiction and Parkinson's disease), acetylcholine (muscle contraction and memory - decline linked to Alzheimer's).
📋 Key Vocabulary and Concepts
For Neurons & Synapses, you must know:
- Sensory neuron
- Motor neuron
- Relay neuron
- Dendrite
- Cell body
- Axon
- Myelin sheath
- Terminal button
- Synapse
- Synaptic cleft
- Neurotransmitter
- Vesicle
- Receptor
- Excitatory
- Inhibitory
- Serotonin
- Dopamine
- Acetylcholine
- Glutamate
- GABA
❓ Practice Questions
Q1: Describe the structure and function of sensory, motor and relay neurons.
Q2: Explain how synaptic transmission works, including the role of neurotransmitters.
Q3: Discuss the role of neurotransmitters in behaviour, referring to serotonin and dopamine.
✅ Answers
- Sensory neurons: carry information from sensory receptors to the CNS (long dendrites, short axons). Motor neurons: carry signals from the CNS to muscles and glands (short dendrites, long axons). Relay neurons: connect sensory and motor neurons within the CNS (short dendrites and axons). Together they form the reflex arc.
- Electrical impulse travels down the axon -> reaches terminal buttons -> vesicles release neurotransmitters into the synaptic cleft -> neurotransmitters diffuse across and bind to receptors on the postsynaptic neuron -> if excitatory signals exceed inhibitory signals, the next neuron fires. The signal is unidirectional (only released from the presynaptic neuron).
- Serotonin regulates mood, sleep and appetite. Low serotonin is linked to depression (SSRIs increase serotonin and treat depression) and aggression. Dopamine is involved in reward, motivation and movement. Excess dopamine is linked to schizophrenia; low dopamine in motor areas causes Parkinson's disease. Both show that chemical imbalances affect behaviour.
🎯 Exam Tips
- Sensory = sense to CNS. Motor = CNS to muscle. Relay = connects them in CNS.
- Synaptic transmission: electrical -> chemical (neurotransmitter) -> electrical. It is ONE-WAY.
- Excitatory = more likely to fire. Inhibitory = less likely to fire. Behaviour depends on the BALANCE.
📝 Exam Technique
Psychology Exam Tips:
When evaluating neurotransmitter research, consider: the relationship is correlational not causal (low serotonin correlates with depression but may not cause it), drug treatments provide indirect evidence, and the brain is more complex than simple chemical imbalance models suggest.
When evaluating neurotransmitter research, consider: the relationship is correlational not causal (low serotonin correlates with depression but may not cause it), drug treatments provide indirect evidence, and the brain is more complex than simple chemical imbalance models suggest.
⚠️ Common Errors
Watch Out!
Students often make mistakes here. Wrong: Neurotransmitters directly cause specific behaviours - low serotonin causes depression. Correct: While low serotonin is consistently associated with depression, this does not prove it causes depression. The relationship could be bidirectional (depression might reduce serotonin), or both could be caused by a third factor (e.g. chronic stress). SSRIs increase serotonin immediately but take weeks to improve mood, suggesting the relationship is more complex than simple cause and effect. The diathesis-stress model suggests biological vulnerability interacts with environmental triggers.
✍️ Model Answer
Full-Mark Response
Evaluate the contribution of neuroscience to our understanding of behaviour, discussing the limitations of neurotransmitter explanations.
A grade 9 response will: describe neurotransmitter functions (serotonin, dopamine, acetylcholine); present supporting evidence (drug treatments, brain scanning studies); evaluate limitations (correlational not causal, reductionist, ignores social/cognitive factors, individual differences in neurotransmitter activity); consider the diathesis-stress model (biological vulnerability + environmental triggers); conclude: neurotransmitter research has made important contributions (especially to understanding mental health and developing drug treatments), but reductionist explanations that ignore psychological and social factors are incomplete. A biopsychosocial approach provides a more comprehensive understanding.
📊 AO Deep Dive
Assessment Objective Focus: Neurons & Synapses
AO1 — Knowledge: Demonstrate knowledge of Neurons & Synapses including key definitions, research studies and psychological terminology.
AO2 — Application: Apply your understanding of Neurons & Synapses to real-world scenarios and given contexts. Use research evidence to support your points.
AO3 — Analysis & Evaluation: Evaluate psychological theories and studies related to Neurons & Synapses, considering methodological strengths and weaknesses, and reaching a balanced conclusion.
📝 Exam Questions by Topic
🎬 Video Resources
Detailed Notes
Key Studies and Theories in Neurons & Synapses
Neurons & Synapses is a core topic in GCSE Psychology that requires understanding of key studies, theories and research methods. The AQA, OCR and Edexcel specifications all require you to know specific studies in detail, evaluate their methodology, and apply psychological concepts to real-life scenarios. When studying neurons & synapses, focus on: the aims, methods, results and conclusions of key studies; the strengths and weaknesses of the research methods used; and how psychological understanding of neurons & synapses applies to everyday life.
Key studies in this area typically use specific research methods such as experiments, observations, self-report (questionnaires and interviews), or correlational analysis. When evaluating studies, consider: reliability (can the study be replicated?); validity (does it measure what it claims to measure?); ethics (were participants protected from harm?); generalisability (can the findings be applied beyond the study sample?); and usefulness (does the research have practical applications?).
GCSE Psychology emphasises the application of psychological knowledge to real contexts. You must be able to explain how understanding of neurons & synapses can be used to improve people’s lives, influence policy, or solve practical problems.
GCSE Example: Key Studies and Theories in Neurons & Synapses
When writing about a study related to neurons & synapses, use the AMRC format: Aim (what was the study trying to find out?), Method (how was it conducted — design, sample, procedure?), Results (what were the key findings?), Conclusions (what do the results mean?).
Evaluating Research in Neurons & Synapses
Evaluation is a crucial skill in GCSE Psychology. When evaluating studies related to neurons & synapses, use the GRAVE method: Generalisability (can the findings be applied to the wider population?), Reliability (are the results consistent if the study is repeated?), Applications (how can the findings be used in real life?), Validity (does the study measure what it claims to measure?), and Ethics (were participants treated ethically?).
Research methods commonly used in neurons & synapses research include: laboratory experiments (high control but low ecological validity), field experiments (more realistic but less control), natural experiments (no manipulation of variables), case studies (in-depth but not generalisable), questionnaires (large samples but social desirability bias), and observations (natural behaviour but ethical concerns). Each method has strengths and limitations that must be evaluated in context.
Ethical issues in neurons & synapses research include: informed consent (participants must agree to take part), debriefing (explaining the true purpose after the study), confidentiality (protecting participants’ identities), protection from harm (no physical or psychological damage), and right to withdraw (participants can leave at any time). The BPS Code of Conduct governs ethical standards in UK psychological research.
GCSE Example: Evaluating Research in Neurons & Synapses
When evaluating Milgram’s obedience study, you might note: low generalisability (all male, American sample); high reliability (standardised procedure with 65% obedience rate); useful applications (understanding wartime atrocities); low ecological validity (artificial laboratory setting); and serious ethical concerns (deception, psychological distress).
Applying Neurons & Synapses to Real Life
GCSE Psychology requires you to apply psychological understanding of neurons & synapses to everyday situations. Consider how the theories and studies you have learned about explain real behaviour: How does neurons & synapses affect people in schools, workplaces, families and communities? What interventions or strategies could improve outcomes based on psychological evidence?
When applying neurons & synapses to real-life scenarios, use the following structure: identify the relevant psychological concept, explain how it applies to the scenario, support your explanation with evidence from a named study, and evaluate the strength of the application (are there limitations or alternative explanations?).
The most effective GCSE Psychology answers show a clear link between theory, evidence and application. Avoid vague statements like ‘psychology can help’ — instead, specify which psychological concept applies, which study supports it, and exactly how it could be used in the given scenario.
GCSE Example: Applying Neurons & Synapses to Real Life
A strong application answer: ‘Understanding of neurons & synapses could help in schools by [specific application]. This is supported by [named study] which found that [specific finding]. This means that [specific practical recommendation]. However, a limitation is [specific weakness of applying this research].’
Comparison Table
| Evaluation Criterion | What It Means | How to Assess It |
|---|---|---|
| Generalisability | Can findings apply beyond the sample? | Consider sample size, representativeness, culture |
| Reliability | Are results consistent if repeated? | Standardised procedures, replicability |
| Validity | Does it measure what it claims? | Ecological validity, construct validity |
| Ethics | Were participants protected? | Consent, debriefing, protection from harm |
| Applications | Is the research useful? | Practical implications, real-world relevance |
Additional Practice Questions
Q: Describe one study related to neurons & synapses and evaluate its methodology using the GRAVE method.
A: A key study in neurons & synapses investigated [aim] using [method] with [sample]. The results showed [key finding], leading to the conclusion that [interpretation]. Evaluation: Generalisability — limited by [sample issue]; Reliability — strengthened by [standardisation]; Applications — useful for [practical application]; Validity — limited by [validity concern]; Ethics — problematic because [ethical issue]. Overall, the study makes a valuable contribution but has limitations that should be considered when applying the findings.
Q: Explain how psychological understanding of neurons & synapses could be applied to improve a real-life situation.
A: Understanding of neurons & synapses can be applied to improve [specific situation]. Research by [named psychologist] found that [key finding], which suggests that [practical recommendation]. For example, in a school context, this understanding could lead to [specific intervention] which would benefit people by [specific improvement]. However, individual differences mean that not everyone will respond the same way, so a personalised approach may be needed.
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