Human Physiology is a core part of IB Biology. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Resting potential≈ -70 mV inside neuron
Action potentialBrief +30 mV spike, all-or-nothing
SynapseGap where neurotransmitter crosses
InsulinLowers blood glucose (β cells)
GlucagonRaises blood glucose (α cells)
ADHIncreases water reabsorption (kidney)
Double circulationPulmonary + systemic loops
Atrium / VentricleReceiving / pumping heart chambers
SA nodePacemaker in right atrium
HaemoglobinTetrameric Fe-protein, O₂ carrier
Bohr shiftCurve shifts right with high CO₂
AlveolusAir sac with thin epithelium
AmylaseHydrolyses starch to maltose
ProteaseHydrolyses protein to amino acids
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Where does digestion begin?✗ In the stomach only. ✓ In the mouth — mechanically by teeth and chemically by amylase in saliva.
What does homeostasis maintain?✗ Conditions that never vary at all. ✓ Stable internal conditions within narrow limits, despite external change.
What does insulin do to blood glucose?✗ Raises blood glucose. ✓ Lowers it, by making cells take up glucose.
How does water enter root hair cells?✗ By active transport using energy. ✓ By osmosis — passively, down a water potential gradient.
How many circuits does human blood flow through per cycle?✗ One single loop around the body. ✓ Two — a double circulation (heart→lungs→heart→body).
Practise Human Physiology — free games
Test yourself with these quick revision games for this topic:
See all 17 games in the Subjects Arcade →
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