Biological Bases of Behaviour
This domain tests how nervous and endocrine activity produces behaviour, with heavy emphasis on neuron parts, brain structures and their functions.
The neuron and the synapse
The neuron's dendrites receive signals, the soma integrates them, the axon conducts the impulse, the myelin sheath speeds it up, and terminal buttons release neurotransmitters into the synaptic cleft. The resting potential is about −70 mV; the action potential is all-or-none. Neurotransmitters either excite or inhibit the next neuron, which is why the synapse, not the neuron alone, is the unit of communication.
Organisation of the nervous system
- Central nervous system: brain and spinal cord.
- Peripheral nervous system: somatic (voluntary movement, sensation) and autonomic.
- Autonomic: the sympathetic branch mobilises the body for fight-or-flight; the parasympathetic branch restores calm.
Brain structures
- Hindbrain: medulla (breathing, heart rate), pons, cerebellum (balance, motor coordination).
- Midbrain: reticular formation (arousal, alertness).
- Forebrain: thalamus (sensory relay), hypothalamus (hunger, thirst, temperature, endocrine control), limbic system - amygdala for emotion and fear, hippocampus for memory consolidation.
- Cerebrum: frontal lobe (planning, movement, Broca's area for speech production), parietal (somatosensory), temporal (hearing, Wernicke's area for comprehension), occipital (vision).
Endocrine glands
Pituitary (the master gland), thyroid (metabolism), adrenal (adrenaline, cortisol), gonads (sex hormones).
Worked example
A patient who cannot form new declarative memories after an infection most plausibly has hippocampal damage, because the hippocampus consolidates new declarative memories. If instead his fear responses were flattened while memory stayed intact, the amygdala would be the better hypothesis.
Traps
Confusing Broca's aphasia (effortful speech production) with Wernicke's (fluent but meaningless speech); calling the sympathetic branch part of the somatic system; describing the left hemisphere as simply 'the logical one'.