IB Biology HL 2.2.9 Action potential propagation Question Bank

Practise IB Biology HL 2.2.9 by applying action potential propagation concepts to exam-style questions.

Exam points

identify the relevant biological structure, process or evidence
apply the correct biological mechanism to the question
evaluate the result using data, adaptation or ecological reasoning

[Maximum number: 4]

Multicellular organisms benefit from cell specialization and division of labour.

Describe what occurs in a neuron when an action potential is propagated along the axon.

a. sodium ions/ $\mathrm{Na}^{+}$ enter/diffuse in;

b. depolarization/membrane potential/voltage changes from negative to positive;

c. potassium channels open AND potassium ions $/ \mathrm{K}^{+}$ exit /diffuse out;

d. repolarization/membrane potential/voltage changes back from positive to negative;

e. local current due to diffusion of sodium ions along the neuron;

f. (local currents) cause next sodium channels to open/next part of axon to depolarize;

g. opening of sodium channels triggered when threshold potential/ -50 mV reached;

Marking guidance:

Do not award mpa for sodium being pumped in (rather than diffusing). Allow mpc with ECF if direction of both sodium and potassium is wrong, or if both movements are described as pumping.

4 max

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C2.2.9 (HL)—Action potential propagation question 1