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C2.2.12 (HL)—Exogenous chemicals

Exogenous chemicals can alter synaptic transmission by blocking receptors, changing neurotransmitter release or preventing neurotransmitter reuptake, linking cellular mechanisms to rapid communication in nervous systems.

Syllabus
First assessment 2025
Objective
C2.2.12
Level
HL

Exam analysis

Chance of appearing17%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"] · TZ33(c)[ 3 ]C2.2.12 (HL)—Exogenous chemicals
May 2025Paper1A ["HL"] · TZ318[ 1 ]C2.2.12 (HL)—Exogenous chemicals
May 2025Paper1A ["HL"] · TZ118[ 1 ]C2.2.12 (HL)—Exogenous chemicals
May 2025Paper1A ["HL"] · TZ217[ 1 ]C2.2.12 (HL)—Exogenous chemicals
May 2024Paper3 ["HL"] · TZ28[ 6 ]C2.2.12 (HL)—Exogenous chemicals
Practice this objective

Coverage 2013–2025 · Updated 15 Jul 2026

Concept essentials

  • Cocaine blocks dopamine reuptake and prolongs postsynaptic stimulation.
  • Neonicotinoids bind acetylcholine receptors in insect postsynaptic membranes.
  • Psychoactive drugs can increase or decrease synaptic transmission.
  • Exogenous chemicals may affect release, receptor binding, breakdown or reuptake of neurotransmitters.
ConceptIB Biology HL