PS15: The Nervous System
Structure and function of the nervous system: the central nervous system (brain and spinal cord), the peripheral nervous system (somatic and autonomic), and the fight-or-flight response.
The Nervous System
Structure and function of the nervous system: the central nervous system (brain and spinal cord), the peripheral nervous system (somatic and autonomic), and the fight-or-flight response.
Key Fact: The nervous system has two main parts: the Central Nervous System (CNS = brain + spinal cord) and the Peripheral Nervous System (PNS = all other nerves connecting the CNS to the body).
Key Fact: The PNS has two divisions: the Somatic Nervous System (controls voluntary movement of skeletal muscles and receives sensory information) and the Autonomic Nervous System (controls involuntary functions like heart rate, digestion, breathing).
Key Fact: The Autonomic Nervous System has two branches: the Sympathetic Nervous System (activates the body for action - increases heart rate, dilates pupils, releases adrenaline - the 'fight-or-flight' response) and the Parasympathetic Nervous System (calms the body - decreases heart rate, constricts pupils, promotes digestion - the 'rest and digest' response).
Key Fact: The fight-or-flight response: when a threat is perceived, the amygdala signals the hypothalamus, which activates the sympathetic nervous system and the endocrine system (adrenal glands release adrenaline). This prepares the body to fight or flee.
Key Fact: The nervous system allows rapid communication: electrical impulses travel along neurons at up to 120m/s. The CNS processes information; the PNS transmits signals to and from the body.
📋 Key Vocabulary and Concepts
For The Nervous System, you must know:
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- Somatic nervous system
- Autonomic nervous system
- Sympathetic nervous system
- Parasympathetic nervous system
- Fight-or-flight response
- Amygdala
- Hypothalamus
- Adrenaline
- Rest and digest
- Homeostasis
❓ Practice Questions
Q1: Describe the structure of the nervous system, distinguishing between the CNS and PNS.
Q2: Explain the fight-or-flight response, including the role of the sympathetic nervous system.
Q3: Evaluate the usefulness of the fight-or-flight response in modern life.
✅ Answers
- CNS: brain and spinal cord - processes information and coordinates responses. PNS: all nerves outside the CNS - connects the CNS to limbs and organs. Somatic: voluntary control (moving your arm). Autonomic: involuntary control (heart beating, digesting).
- When a threat is detected: amygdala -> hypothalamus -> sympathetic nervous system activated -> adrenaline released -> heart rate increases, breathing speeds up, pupils dilate, blood diverted to muscles, digestion pauses -> body is prepared to fight or flee. After the threat passes, the parasympathetic system restores calm.
- Useful: rapid response to physical threats (avoiding a car, escaping danger). Limitations in modern life: most modern 'threats' are psychological (exams, public speaking, social media), where physical fight-or-flight is unhelpful - chronic stress can lead to health problems (heart disease, anxiety, immune suppression). The response evolved for physical dangers but is triggered by psychological stressors.
🎯 Exam Tips
- CNS = brain + spinal cord. PNS = everything else. Somatic = voluntary. Autonomic = involuntary.
- Sympathetic = FIGHT or FLIGHT (activates). Parasympathetic = REST and DIGEST (calms).
- Fight-or-flight: amygdala -> hypothalamus -> sympathetic -> adrenaline.
📝 Exam Technique
Psychology Exam Tips:
When evaluating the nervous system, consider: is the fight-or-flight response still adaptive? How does chronic activation affect health? Are there individual differences in stress responses? Link to psychological problems (anxiety, PTSD).
When evaluating the nervous system, consider: is the fight-or-flight response still adaptive? How does chronic activation affect health? Are there individual differences in stress responses? Link to psychological problems (anxiety, PTSD).
⚠️ Common Errors
Watch Out!
Students often make mistakes here. Wrong: The fight-or-flight response is always helpful because it prepares us to deal with threats. Correct: While fight-or-flight is adaptive for acute physical threats, it is maladaptive for chronic psychological stress. When the sympathetic nervous system is repeatedly activated (e.g. work stress, exam anxiety), prolonged adrenaline and cortisol release can cause: high blood pressure, weakened immune system, anxiety disorders, and digestive problems. The response evolved for short-term physical dangers, not ongoing psychological pressure.
✍️ Model Answer
Full-Mark Response
Evaluate the effectiveness of the fight-or-flight response in dealing with modern stressors.
A grade 9 response will: describe the fight-or-flight response (amygdala, hypothalamus, sympathetic activation, adrenaline); explain its evolutionary value (rapid preparation for physical threats); evaluate for modern life (most stressors are psychological and chronic; physical preparation is unhelpful; chronic activation causes health problems - heart disease, anxiety, immune suppression); discuss individual differences (some people show a 'freeze' response; not everyone responds the same way); conclude: the fight-or-flight response is highly effective for acute physical threats but can be harmful when triggered repeatedly by chronic psychological stressors. Stress management techniques (deep breathing, exercise) activate the parasympathetic system and counteract these effects.
📊 AO Deep Dive
Assessment Objective Focus: The Nervous System
AO1 — Knowledge: Demonstrate knowledge of The Nervous System including key definitions, research studies and psychological terminology.
AO2 — Application: Apply your understanding of The Nervous System to real-world scenarios and given contexts. Use research evidence to support your points.
AO3 — Analysis & Evaluation: Evaluate psychological theories and studies related to The Nervous System, considering methodological strengths and weaknesses, and reaching a balanced conclusion.
📝 Exam Questions by Topic
🎬 Video Resources
Detailed Notes
Key Studies and Theories in The Nervous System
The Nervous System 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 the nervous system, 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 the nervous system 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 the nervous system can be used to improve people’s lives, influence policy, or solve practical problems.
GCSE Example: Key Studies and Theories in The Nervous System
When writing about a study related to the nervous system, 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 The Nervous System
Evaluation is a crucial skill in GCSE Psychology. When evaluating studies related to the nervous system, 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 the nervous system 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 the nervous system 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 The Nervous System
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 The Nervous System to Real Life
GCSE Psychology requires you to apply psychological understanding of the nervous system to everyday situations. Consider how the theories and studies you have learned about explain real behaviour: How does the nervous system affect people in schools, workplaces, families and communities? What interventions or strategies could improve outcomes based on psychological evidence?
When applying the nervous system 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 The Nervous System to Real Life
A strong application answer: ‘Understanding of the nervous system 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 the nervous system and evaluate its methodology using the GRAVE method.
A: A key study in the nervous system 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 the nervous system could be applied to improve a real-life situation.
A: Understanding of the nervous system 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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