Biological Bases of Behaviour: Nervous System, Endocrine System and Genetics
This domain tests how biological structures produce behaviour: the divisions of the nervous system, neuron and synapse, brain areas, hormones and genetic inheritance. Expect labelling-style recall and applied questions on arousal and inheritance.
Nervous system
- CNS = brain and spinal cord; PNS = somatic and autonomic divisions.
- Autonomic: sympathetic (fight-or-flight: faster heart, dilated pupils, inhibited digestion) and parasympathetic (rest-and-digest, vagus nerve).
- Neuron: dendrites receive, soma integrates, axon conducts, myelin speeds transmission, terminal buttons release neurotransmitter across the synapse.
- Key transmitters: acetylcholine, dopamine, serotonin, norepinephrine, GABA.
- Brain: frontal (motor, planning), parietal (somatosensory), temporal (auditory), occipital (visual); hypothalamus regulates hunger, temperature and the endocrine link; cerebellum balances; medulla controls vital reflexes.
Endocrine system
- The pituitary is called the master gland but is controlled by the hypothalamus. Hormones travel in blood, acting more slowly and for longer than neural signals.
- Thyroid (metabolism), adrenal (cortisol, epinephrine), pancreas (insulin), gonads (sex hormones).
Genetics
- 46 chromosomes in 23 pairs; DNA and genes; genotype versus phenotype; dominant and recessive alleles; polygenic traits.
- Heritability is estimated from twin and adoption studies.
Worked example
A student is startled: pupils dilate, heart races, digestion slows. Reasoning: sympathetic activation, with epinephrine from the adrenal medulla; the parasympathetic branch later restores baseline.
Traps
- Pituitary versus hypothalamus.
- Sympathetic means arousal, not calming.
- Heritability is population-level, not an individual percentage.