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IB DP Psychology — Biological Approach | SL & HL | Paper 1
🎯 Learning Intentions By the end of this note, you will be able to:
- Define neurotransmitter, synapse, and neurotransmission using IB-aligned terminology.
- Explain how neurotransmitters are released, travel across the synapse, and bind to receptors to influence behaviour.
- Describe the roles of serotonin, dopamine, and acetylcholine in regulating mood, motivation, and cognition.
- Evaluate research evidence for the role of neurotransmitters in behaviour using supporting and opposing studies in ACAS format.
- Apply neurotransmission concepts to a real-world case study from the biological perspective.
- Discuss the extent to which neurotransmitter activity provides a complete explanation of human behaviour.
- Analyse research on neurotransmission using relevant concept areas: Causality, Bias, Perspective, and Responsibility.
Introduction & Context
Have you ever wondered why a cup of coffee makes you feel more alert, or why a frightening experience can leave your heart racing long after the danger has passed? These experiences feel entirely psychological — they involve thoughts, feelings, and perceptions — yet they are rooted in something deeply physical: the chemical signals passing between billions of nerve cells inside your brain and body.
The brain is not a single organ that thinks in isolation. It is an extraordinarily complex network of neurons — specialised cells that communicate with one another constantly. The way these cells talk to each other, and the chemical language they use, shapes almost everything we experience: how happy or sad we feel, how focused or distracted we are, whether we feel hungry, calm, anxious, or motivated. Understanding this chemical communication system is one of the most important foundations of the biological approach to psychology.
Before we introduce any formal terminology, consider this: if two people need to pass a message to each other but cannot touch, they must throw the message across a gap. The receiver catches it, reads it, and responds. This is essentially what happens between neurons — and the "message" is a chemical substance. The gap between neurons, the chemical messenger, and the receiving cell are all central to the concept we are about to explore.
🔁 Analogy — The Post Office Model Imagine a nationwide postal system. Each post office (neuron) receives letters, processes them, and sends new letters to the next post office down the line. The letters themselves are the chemical messengers. The road between two post offices is the synapse — a tiny gap. The receiving post office has a special letterbox (receptor) that only accepts certain shapes of envelope. If the letter fits, the message is delivered and the next post office responds. If the letterbox is blocked or the wrong letter arrives, communication breaks down. This is precisely how neurotransmission works: the right chemical must fit the right receptor for a message to be passed along.
Core Concepts
To understand how the brain influences behaviour, we first need to understand the basic unit of communication in the nervous system: the neuron. Neurons are specialised cells that carry electrical signals. However, neurons do not physically touch one another — there is always a tiny gap between them. The question is: how does a signal jump across that gap?
📖 Key Definition —