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Unit 2: Maintaining the internal environment

8 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

Topic 1: Homeostasis

Explain thermoregulation in endotherms and ectotherms, including behavioural and physiological responses to heat and cold

Thermoregulation. Contrasts endotherms and ectotherms, lists behavioural and physiological responses to heat (sweating, vasodilation) and cold (shivering, vasoconstriction), and connects each to negative feedback through the hypothalamus.

8 min read →

Describe endocrine control of the internal environment, including the role of hormones, target cells, the hypothalamus and pituitary gland, and the regulation of blood glucose by insulin and glucagon

Endocrine control. Defines hormones, distinguishes steroid and peptide signalling at target cells, lays out the hypothalamic-pituitary axis and traces blood glucose regulation by insulin and glucagon as a negative feedback loop.

9 min read →

Describe nervous control, including the structure of a neuron, the generation of action potentials, synaptic transmission and the reflex arc

Nervous control. Describes the structure of a neuron (dendrites, soma, axon, myelin sheath), the three phases of an action potential, chemical synaptic transmission and the five components of a reflex arc.

9 min read →

Describe osmoregulation and excretion in mammals, including the structure and function of the nephron and the role of ADH in regulating water balance

Osmoregulation. Walks through the four processes of the nephron (filtration, reabsorption, secretion, excretion), names each region (glomerulus, PCT, loop of Henle, DCT, collecting duct) and explains the role of ADH in adjusting urine concentration through negative feedback.

9 min read →

Explain the concept of homeostasis and the role of negative feedback in maintaining a stable internal environment, including stimulus, receptor, control centre, effector and response

Homeostasis. Defines homeostasis around a set point, lays out the stimulus to receptor to control centre to effector to response pathway, contrasts negative and positive feedback and uses thermoregulation and blood glucose as worked examples.

8 min read →

Topic 2: Infectious disease and the immune response

Explain how vaccines work, the role of herd immunity, and the development and implications of antibiotic resistance for human health

Vaccines and antibiotic resistance. Explains how vaccines trigger a primary response to leave memory cells, defines herd immunity and the thresholds that protect communities, and walks through how antibiotic resistance evolves and what it means for public health.

9 min read →

Describe the main groups of pathogens (bacteria, viruses, fungi, protists, prions) and their modes of transmission, distinguishing between communicable and non-communicable disease

Pathogens. Names the five pathogen groups (bacteria, viruses, fungi, protists, prions) with a named human disease for each, lists the main modes of transmission (direct contact, droplet, airborne, vector, waterborne, foodborne, blood-borne) and distinguishes communicable from non-communicable disease.

8 min read →

Describe the first, second and third lines of defence in vertebrates, including innate immune responses (barriers, inflammation, phagocytes) and adaptive immune responses (humoral immunity through B cells and antibodies, cell-mediated immunity through T cells)

Immune response. Names the first, second and third lines of defence, walks through the inflammatory response and phagocytosis (innate), then contrasts humoral immunity (B cells, antibodies) and cell-mediated immunity (T cells) including immunological memory.

10 min read →