B3.3.4 (HL)—Motor units
Motor units connect motor neurons to muscle fibres, where impulses at motor end plates trigger neurotransmitter release and start contraction.
- Syllabus
- First assessment 2025
- Objective
- B3.3.4
- Level
- HL
Exam analysis
Chance of appearing1%of analysed past papers
Latest appearanceNovember 2017
Most common paperPaper1
Typical marks1
Common command terms
- Identify
Recent exam appearances
November 2017Paper1 ["HL"] · TZ024[ 1 ]B3.3.4 (HL)—Motor units
Practice this objective
Coverage 2017–2017 · Updated 15 Jul 2026
Concept essentials
- An action potential at the motor end plate causes neurotransmitter release.
- Neuromuscular junctions link motor neurons to skeletal muscle fibres.
- Excitation of the sarcolemma leads to calcium release inside the fibre.
- Motor units convert neural signals into coordinated muscle contraction.