How do the nervous system and the brain produce behaviour?
Explain how neurons, the nervous system and brain structures underpin human behaviour.
How neurons, neurotransmitters, the nervous system and brain regions produce behaviour, drawing on Phineas Gage, split-brain research and the lock-and-key model.
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What this dot point is asking
The biological approach assumes that all thought, emotion and behaviour have a physical basis in the nervous system. To answer this dot point you build from the smallest unit (the neuron) up to whole brain structures.
The neuron and the synapse
The neuron is the basic cell of the nervous system. A typical neuron has dendrites (which receive signals), a cell body (soma), and an axon (which carries the signal away). Many axons are wrapped in a myelin sheath that speeds transmission.
Communication within a neuron is electrical: when stimulation reaches a threshold, the neuron "fires" an action potential, an all-or-none electrical impulse that travels down the axon. Communication between neurons is chemical. At the synapse (the tiny gap between neurons), the action potential triggers the release of neurotransmitters from the presynaptic neuron. These chemicals cross the gap and bind to receptors on the next neuron.
Key neurotransmitters to know: dopamine (reward, movement; depleted in Parkinson's disease), serotonin (mood, sleep; targeted by SSRIs for depression), and GABA (the main inhibitory transmitter, calming neural activity).
Organisation of the nervous system
The nervous system divides into two parts:
- Central nervous system (CNS): the brain and spinal cord.
- Peripheral nervous system (PNS): all nerves outside the CNS.
The PNS splits into the somatic nervous system (voluntary skeletal muscle and sensory input) and the autonomic nervous system (involuntary control of organs). The autonomic system in turn has the sympathetic branch (the "fight-or-flight" arousal response, increasing heart rate and releasing adrenaline) and the parasympathetic branch (the "rest-and-digest" response that returns the body to baseline).
Brain structures and localisation of function
Localisation of function is the idea that specific brain areas carry out specific tasks. Useful structures to name:
- Cerebral cortex, divided into four lobes: frontal (planning, decision-making, personality, motor control), parietal (touch and spatial processing), temporal (hearing, memory, language comprehension), and occipital (vision).
- Cerebellum: coordination, balance and fine motor control.
- Hippocampus: forming new long-term memories.
- Amygdala: emotional responses, especially fear and aggression.
- Hypothalamus: homeostasis, hunger, thirst and hormone regulation.
Hemispheric specialisation
The cortex has two hemispheres joined by the corpus callosum. Sperry and Gazzaniga's split-brain studies (1960s) tested patients whose corpus callosum had been cut to treat epilepsy. When an object was shown only to the right visual field (left hemisphere), patients could name it; when shown only to the left visual field (right hemisphere), they could not name it but could select it by touch with the left hand. This demonstrated that language is typically lateralised to the left hemisphere and that the two hemispheres can process information independently.
Language areas are also localised: Broca's area (frontal lobe) governs speech production, and Wernicke's area (temporal lobe) governs language comprehension. Damage to each produces a different type of aphasia.
Putting it together
A strong answer moves up the levels: a neuron fires and releases a neurotransmitter, networks of neurons form structures, structures specialise in functions, and these functions combine to produce behaviour. Naming evidence (Gage for the frontal lobe, Sperry and Gazzaniga for lateralisation, the lock-and-key model for chemical transmission) shows the marker that you can connect biology to observable behaviour rather than just listing parts.
Exam-style practice questions
Practice questions written in the style of TASC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
TCE 20236 marksDescribe how a message travels within and between neurons, using the terms action potential, synapse, neurotransmitter and receptor. Include the lock-and-key model in your answer.Show worked answer →
This is a short-answer item marked on Criterion 3. Build the answer in order from within a neuron to between neurons.
- Within a neuron (electrical)
- When stimulation at the dendrites reaches a threshold, the neuron fires an action potential, an all-or-none electrical impulse that travels down the axon (faster where the axon is myelinated).
- Between neurons (chemical)
- At the synapse, the tiny gap between neurons, the action potential triggers the release of neurotransmitters from the presynaptic neuron into the gap.
- Reception
- The neurotransmitters cross the synapse and bind to receptors on the next (postsynaptic) neuron. By the lock-and-key model, a neurotransmitter only activates a receptor with a matching shape, which is why dopamine, serotonin and GABA each have specific effects.
Markers reward correct sequencing and accurate use of all the required terms.
TCE 20218 marksLocalisation of function means specific brain areas carry out specific tasks. Discuss the evidence for localisation, referring to at least one case study and one research method, and note one limitation of the localisation view.Show worked answer →
This is an extended item marked on Criteria 3 and 7. Define, evidence, then evaluate.
- Definition
- Localisation of function is the idea that particular brain structures are responsible for particular functions, for example the occipital lobe for vision and Broca's area for speech production.
- Case-study evidence
- Phineas Gage (1848) survived an iron rod through his frontal lobe and reportedly showed major personality change, providing early evidence that the frontal lobe supports personality, planning and self-control.
- Research-method evidence
- Sperry and Gazzaniga's split-brain studies cut the corpus callosum and showed patients could name objects shown to the left hemisphere but not the right, demonstrating language is lateralised to the left hemisphere.
- Limitation
- Strict localisation overstates the case: most complex behaviour uses networks across both hemispheres, and the brain shows plasticity, with other regions sometimes taking over lost functions. A balanced answer accepts localisation for some functions while recognising distributed processing.
Markers reward named evidence of two types and a genuine limitation.