IB Biology HL C2.2.8 Hl Depolarization and Repolarization Questions

Practise IB Biology HL 2.2.8 by applying depolarization and repolarization concepts to exam questions.

Exam points

Explain how voltage-gated sodium channels open at threshold and sodium influx depolarizes the axon.
Explain how voltage-gated potassium channels open after sodium-channel closure and potassium efflux repolarizes or briefly hyperpolarizes the axon.
Interpret action-potential graphs using threshold potential, ion movements, channel timing and the sequence of depolarization and repolarization.

[Maximum number: 2]

Cholinergic synapses use acetylcholine as their neurotransmitter. They are widespread in the body, passing on signals to muscle cells. These synapses are affected by neonicotinoid pesticides.

The diagrams, which are not drawn to scale, show the synapse between two neurons and a detail of the synaptic cleft.

Figure for Question IB Biology HL C2.2.8 Hl Depolarization and Repolarization Questions question 1 — IB Biology HL

Outline how depolarization of the membrane of an axon occurs.

a. (local depolarization) causes ion / sodium / voltage gated channels to open /
b. altering membrane permeability to sodium ions/ $\mathrm{Na}^{+} /$ positive ions $/ \mathrm{Na}^{+}$ diffuses into the cytoplasm
c. membrane potential (of the axon) changes from negative to positive
d. a threshold potential is reached and an action potential is generated

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IB Biology HL C2.2.8 Hl Depolarization and Repolarization Questions question 1