IB Biology HL C2.2.8 Hl Depolarization and Repolarization Questions

Review how voltage-gated Na⁺ channels drive axon depolarization, then how K⁺ channels restore the membrane potential and may briefly hyperpolarize it.

Exam points

Explain how reaching threshold opens voltage-gated Na⁺ channels; Na⁺ influx depolarizes the axon membrane.
Explain how voltage-gated K⁺ channels open after depolarization; K⁺ efflux repolarizes the membrane and may briefly hyperpolarize it when channels close slowly.

[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