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C2.2.6—Neurotransmitter release

Neurotransmitter release occurs when presynaptic depolarization opens calcium channels and calcium triggers vesicle fusion with the presynaptic membrane, linking cellular mechanisms to rapid communication in nervous systems.

Syllabus
First assessment 2025
Objective
C2.2.6
Level
HL

Exam analysis

Chance of appearing5%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper3
Typical marks1–6

Common command terms

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Recent exam appearances

November 2025Paper2 ["HL"] · TZ18(b)[ 7 ]C2.2.6—Neurotransmitter release
November 2023Paper3 ["HL"] · TZ26(a)(ii)[ 1 ]C2.2.6—Neurotransmitter release
November 2020Paper2 ["HL"] · TZ02(c)(ii)[ 3 ]C2.2.6—Neurotransmitter release
May 2018Paper3 ["HL"] · TZ27(b)[ 1 ]C2.2.6—Neurotransmitter release
November 2016Paper3 ["HL"] · TZ08[ 6 ]C2.2.6—Neurotransmitter release
Practice this objective

Coverage 2012–2025 · Updated 15 Jul 2026

Concept essentials

  • An arriving action potential depolarizes the presynaptic terminal.
  • Calcium ions enter the presynaptic neuron through calcium channels.
  • Calcium triggers vesicle fusion with the presynaptic membrane.
  • Neurotransmitters are released into the synaptic cleft by exocytosis.
ConceptIB Biology HL