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Depolarisation

A generator potential causes sodium ions to enter the neurone through the (stretch-mediated) sodium channels in the membrane.This causes a change in potential from negative inside the membrane to more positive. If the potential reaches a threshold value then all the sodium voltage-gated channels in the membrane open (positive feedback) causing an influx of sodium ions by diffusion into the neurone. The membrane potential rises to +40mV. This is called depolarisation.

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Specification: OCR Biology A (H420), A-level, 5.1.3 Neuronal communication. Topic: Neuronal Communication.

Key terms in this lesson

Sarcomere
The contractile unit of a myofibril, delineated by two Z-lines, containing overlapping actin and myosin filaments.
Actin
A thin protein filament in a myofibril that, together with myosin, slides during muscle contraction.
Myosin
A thick protein filament in a myofibril with globular heads that bind to actin and pull it during muscle contraction.
ATP
Adenosine triphosphate, the universal energy currency of cells, which releases energy for cellular reactions when hydrolysed to ADP and inorganic phosphate.

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All 38 lessons in Neuronal Communication · All OCR A-level Biology topics