Cells constantly send and receive signals. This HL lesson covers C2.1 Chemical signalling (HL) and C2.2 Neural signalling.
You will study signal types, membrane and intracellular receptors, second-messenger cascades, and the action potential and synapse.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
Cells communicate with chemical signals: neurotransmitters, hormones, cytokines, and even bacterial quorum sensing.
Agonists activate receptors; antagonists block them — the basis of many drugs.
A neuron rests at about −70 mV. When a stimulus reaches threshold, voltage-gated sodium channels open and Na⁺ rushes in, causing depolarisation. Potassium then leaves to repolarise.
Impulses are all-or-none and travel by saltatory conduction along myelinated axons. Summation lets several sub-threshold inputs combine to fire an impulse.
Sort each term into signal, receptor mechanism, or neural signalling.
At a synapse, an action potential triggers Ca²⁺ entry, releasing neurotransmitter that crosses the gap and binds receptors on the next cell.
Excitatory inputs depolarise; inhibitory inputs hyperpolarise. The postsynaptic neuron sums these to decide whether to fire — the basis of neural integration.
Match each signalling term to its meaning.
C2.1 (HL): signal types; membrane vs intracellular receptors; second messengers; agonists/antagonists
C2.2: resting and action potentials; Na in (depolarise), K out (repolarise)
C2.2: synapses release neurotransmitter; excitation, inhibition and summation
Skills: speed = distance / time; time = distance / speed
Press Finish to see your score.
You have worked through Theme C: Interaction — Cell Signalling for IB Diploma Biology. 🎉
Your stars: 0 / 0
Next: test yourself in the Evaluate stage Confidence Quiz, then lock it in with Verify.