Action Potential

• Once voltage reaches -55mV it causes wave of depolarisation (electrical impulse); occurs on the all or nothing principle: it is same size and only occurs if specific value is reached
• More voltage-gated Na+ channels open, and more Na^+ ions flood in making it more positive than outside until it reaches maximum (40mV)
• It is a rapid, brief and temporary depolarisation of neurone cell surface membrane, caused by stimulus to membrane
• Calculate time from first increase in membrane potential (when Na+ voltage gated channels open) to when resting potential is resumed (just after hyperpolarisation) for length of action potential
• Repolarisation: Eventually Na^+ channels close and K+ channels open, more K+ ions diffuse out down their gradient, bringing membrane back to resting potential