All-or-none law
What All-or-none law means in Physical Education A-Level, as defined for AQA.
Definitions of All-or-none law
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Reference: AQA
When a motor neurone is stimulated, all the muscle fibres within that specific motor unit contract maximally; if the stimulus is below the threshold, none of the fibres contract.
When a unit's motor neurone fires, every fibre in that unit contracts fully, so stronger contraction comes from recruiting more units and raising firing frequency.
Once a stimulus reaches threshold at a muscle fibre, that fibre contracts to its maximum possible extent for its current condition.
Topics that use All-or-none law
- Neuromuscular system (AQA A-Level)
Related terms
- Aerobic and anaerobic ATP resynthesis
- Aerobic ATP resynthesis
- Aerobic oxidation
- Calcium ion retention
- Calcium ions
- Endurance activity performance
- Fast glycolytic (type IIx)
- Fatigue resistance
Using All-or-none law in the exam
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