IB Biology SL C2.2.3 Nerve Impulses As Action Potentials Questions

Practise IB Biology SL 2.2.3 by explaining how ion movement creates and transmits an action potential.

Exam points

Explain how sodium influx depolarizes the membrane and potassium efflux repolarizes it during an action potential.
Describe how an action potential propagates along a nerve fibre and identify its axonal location.
Identify resting and depolarized regions on a nerve-fibre diagram.

[Maximum number: 3]

The diagram below shows a motor neuron.

Motor-neuron drawing ending on muscle fibres. I points to the dark oval in the cell body, II to the long central fibre, III to a segmented covering and IV to branches extending from the cell body. Blank label lines accompany I–IV.

Outline how nerve impulses are transmitted along a nerve fibre.

a. (sodium channels/voltage-gated channels open and) $\mathrm{Na}^{+}$ diffuse into neuron (down concentration gradient);
b. inside of neuron becomes positive compared to outside / potential is reversed / depolarization;
c. wave of depolarization moves (down the membrane);
d. (potassium channels open and) $\mathrm{K}^{+}$ diffuse out (down concentration gradient);
e. inside becomes negative compared with outside / potential across membrane restored / repolarization;
f. active transport of $\mathrm{K}^{+}$ (into neuron) and $\mathrm{Na}^{+}$ (out of neuron) restores resting potential;

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IB Biology SL C2.2.3 Nerve Impulses As Action Potentials Questions question 1