The action potential Outside the cellInside the cellPumpATPK⁺ leakK⁺ leakVoltage-gatedNa⁺ channelinactivatedVoltage-gatedK⁺ channel+++++−−−−−−−−−−+++++Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺K⁺K⁺K⁺K⁺K⁺K⁺K⁺K⁺K⁺K⁺K⁺Na⁺Na⁺K⁺K⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺Na⁺K⁺K⁺K⁺K⁺Na⁺K⁺StimulusMembrane potential (mV)Time−850+30ThresholdDepolarisationRepolarisationBrief undershootNa⁺Na⁺ (sodium)K⁺K⁺ (potassium)1At rest2Stimulus to threshold3Sodium rushes in4Potassium flows out5ResetVery few ions actually moved
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