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WAHuman Biology

Unit 3: Homeostasis and Disease

12 dot points across 12 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What happens to the body when homeostatic control mechanisms fail or are overwhelmed?

Explain how disease, malfunction of feedback systems and environmental factors disrupt homeostasis, using named examples such as diabetes
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on disrupted homeostasis. Causes of disease, feedback failure, diabetes type 1 and 2, and how disrupted variables damage cells.
8 min answer →

How does the body keep its internal environment stable when conditions outside keep changing?

Explain how stimulus-response models and negative feedback maintain a stable internal environment within tolerance limits
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on homeostasis. The stimulus-response model, the receptor-control centre-effector pathway, why negative feedback dominates, and how to write a feedback loop in the exam.
7 min answer →

How do vaccines protect a whole community, and why are antibiotics losing their power against bacteria?

Explain how immunisation produces artificial active immunity, how herd immunity protects a population, and how antibiotic use and resistance affect the control of infectious disease
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on disease control. How vaccines create artificial active immunity and memory cells, how herd immunity protects a population, and how antibiotics work and why resistance evolves.
7 min answer →

How is the nervous system divided up so that some responses are voluntary and others run automatically?

Describe the organisation of the nervous system into central and peripheral divisions, and the somatic and autonomic (sympathetic and parasympathetic) divisions and their roles in homeostasis
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on how the nervous system is organised. The central and peripheral divisions, the somatic and autonomic systems, and the antagonistic sympathetic and parasympathetic branches in homeostasis.
6 min answer →

What are the different types of disease-causing agents and how do they spread between people?

Classify pathogens and the diseases they cause, describe modes of transmission, and use epidemiological terms such as incidence, prevalence and reservoir to describe the spread of disease
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on pathogens and transmission. Types of pathogens with named diseases, the modes of disease transmission, and the epidemiology terms used to describe how disease spreads through a population.
7 min answer →

How does the body defend itself against pathogens and remember the ones it has already met?

Describe the lines of defence against pathogens, including non-specific defences and the specific immune response with B and T lymphocytes
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on immunity. Pathogen types, the three lines of defence, humoral and cell-mediated responses, memory cells, and active versus passive immunity.
9 min answer →

How does the body keep blood glucose steady between meals and after eating a sugary snack?

Explain how blood glucose concentration is regulated by negative feedback, including the roles of the pancreas, insulin and glucagon and the liver
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on blood glucose regulation. The islets of Langerhans, the antagonistic action of insulin and glucagon, the liver as the main effector, and how the negative feedback loop runs in both directions.
7 min answer →

How do the kidneys keep the water and salt content of the blood constant whether you drink a litre of water or sweat it out?

Explain how body fluid composition is regulated, including the role of the kidney and nephron, antidiuretic hormone and aldosterone in osmoregulation by negative feedback
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on osmoregulation. The nephron and the three stages of urine formation, the role of antidiuretic hormone in water balance, and aldosterone in salt balance, all as negative feedback.
8 min answer →

How does the body hold its core temperature near 37 degrees whether it is freezing or sweltering outside?

Explain how the body regulates core temperature by negative feedback, including the role of the hypothalamus, thermoreceptors and the effectors that control heat loss and heat gain
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on thermoregulation. The hypothalamus and thermoreceptors, the effectors for heat loss (sweating, vasodilation) and heat gain (shivering, vasoconstriction), and the four routes of heat transfer.
7 min answer →

How do hormones coordinate slow, widespread and sustained responses across the body?

Describe how endocrine glands secrete hormones that regulate target cells, using thermoregulation and blood glucose regulation as examples
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on the endocrine system. How hormones reach target cells, steroid versus protein hormone action, and worked negative-feedback loops for blood glucose and thyroxine.
8 min answer →

How does a nerve cell turn a stimulus into an electrical signal that travels the length of an axon?

Explain the resting membrane potential, the generation and propagation of the action potential, the all-or-none principle, the refractory period and saltatory conduction
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on the nerve impulse. The resting potential and sodium-potassium pump, depolarisation and repolarisation, the all-or-none principle, the refractory period, and how myelin produces saltatory conduction.
7 min answer →

How does the nervous system detect change and respond within a fraction of a second?

Describe the structure and function of neurons, the transmission of nerve impulses, synaptic transmission and the reflex arc in homeostatic control
A focused answer to the WACE Year 12 Human Biology Unit 3 dot point on the nervous system. Neuron structure, the action potential and saltatory conduction, synaptic transmission with neurotransmitters, and the reflex arc.
8 min answer →