Biological Bases of Behaviour: Nervous System, Endocrine System and Genetics
This domain moves from the single neuron to glands and genes. Expect labelling of the nervous system, function-matching for brain areas, hormone–gland pairing, and clear distinction between genotype and phenotype.
Neuron and synapse
- Dendrites receive, soma integrates, axon conducts, myelin speeds conduction, terminal buttons release neurotransmitters.
- Resting potential is about −70 mV; the action potential is all-or-none; transmission across the synapse is chemical.
- Transmitters: acetylcholine (muscle, memory), dopamine (movement, reward), serotonin (mood, sleep), noradrenaline (arousal), GABA (inhibition), endorphins (pain relief).
Nervous system
- CNS = brain + spinal cord; PNS = somatic (voluntary) + autonomic (involuntary).
- Sympathetic division prepares fight-or-flight (faster heart, dilated pupils, dry mouth); parasympathetic restores rest-and-digest.
- Hindbrain: medulla (respiration, heart), pons, cerebellum (balance, coordination). Midbrain: reflexes, visual–auditory relay. Forebrain: thalamus (sensory relay), hypothalamus (hunger, thirst, temperature, endocrine control), limbic system - amygdala (emotion), hippocampus (memory consolidation); cerebrum with frontal (motor, planning, Broca's area), parietal (touch), temporal (hearing, Wernicke's area) and occipital (vision) lobes.
Endocrine and genetics
- Pituitary is the master gland but is controlled by the hypothalamus; thyroid (thyroxine, metabolism), adrenal (adrenaline, cortisol), pancreas (insulin), gonads (sex hormones), pineal (melatonin).
- 46 chromosomes in 23 pairs; genotype versus phenotype; dominant and recessive alleles; twin and adoption studies estimate heritability.
Worked example
A student's pupils dilate and heart races before a viva. The hypothalamus activates the sympathetic branch, which stimulates the adrenal medulla to release adrenaline; heart rate and pupil size change. The bodily change is the output of autonomic activation, not the cause of the situation.
Traps
- Cerebellum is balance, not memory; hippocampus is memory, not emotion.
- The pituitary is called master gland but obeys hypothalamic signals.
- Do not confuse sympathetic with parasympathetic effects.