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VCE Units 1–4 · Biology

VCE Biology — Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes. In VCE Biology, the key examples are thermoregulation, blood glucose regulation and the immune response. All three follow the same negative feedback principle — a change is detected and corrected — but each uses different organs, hormones and mechanisms.

Key Concepts & Formulas

  • Negative feedback: a change from the set point triggers a response that REVERSES the change and restores the set point

  • Thermoregulation: hypothalamus detects body temperature changes and coordinates responses

  • When too hot: vasodilation (increased blood flow to skin), sweating (evaporative cooling), decreased metabolic rate

  • When too cold: vasoconstriction, shivering (muscle contraction generates heat), increased metabolic rate, piloerection

  • Blood glucose regulation: pancreas detects blood glucose levels

  • Hyperglycaemia: beta cells secrete insulin → cells take up glucose; liver converts glucose to glycogen (glycogenesis)

  • Hypoglycaemia: alpha cells secrete glucagon → liver breaks down glycogen to glucose (glycogenolysis)

  • Innate (non-specific) immunity: first line (skin, mucus); second line (inflammation, fever, phagocytes) — fast, non-specific

  • Adaptive (specific) immunity: third line; involves B lymphocytes (antibodies) and T lymphocytes (cell-mediated) — slow first time, faster on re-exposure (memory)

  • Antigen: a molecule (usually foreign protein) that triggers an immune response; antibody: Y-shaped protein that binds specifically to one antigen

Practice Questions

5 questions

Attempt each question before reading the hint. These are styled to match VCE exam format.

Q1.Explain how negative feedback operates in the regulation of blood glucose levels after a meal, naming the hormone involved and its site of production.

4 marks

Q2.Compare the first and third line defences against pathogens in terms of specificity and speed of response.

4 marks

Q3.A person goes for a run on a hot day. Describe TWO physiological responses that help regulate their body temperature back to 37°C.

4 marks

Q4.Explain why a second infection by the same pathogen results in a faster and stronger immune response than the first infection.

3 marks

Q5.Distinguish between the roles of B lymphocytes and T lymphocytes in the adaptive immune response.

4 marks

Common Mistakes to Avoid

These are the errors that VCE students most frequently make in Homeostasis — and that examiners are specifically watching for.

  • Saying insulin "breaks down" glucose — insulin promotes uptake of glucose by cells and conversion to glycogen, it does not break glucose down

  • Confusing glucagon and insulin effects: insulin LOWERS blood glucose; glucagon RAISES blood glucose

  • Saying the immune system "destroys" antigens — antibodies BIND to antigens (marking them for destruction); phagocytes engulf and destroy them

  • Describing positive feedback instead of negative feedback — homeostasis always uses negative feedback to restore the set point

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