Can you explain the main events that happen during an action potential?
What is an action potential? When a stimulus of sufficient size is detected, it causes a temporary reversal of charges either side of the axon membrane. It also causes the channels in the axon membrane to change shape, (to open/close) A nerve impulse in an unmyelinated neurone can be split in to 5 main events STIMULUS- causes some Na+ voltage gated channels to open, causing Na+ to diffuse down an electrochemical gradient into the neurone. DEPOLARISATION - The inner membrane becomes more positive as Na+ diffuses in. When the threshold value is reached, (approx. -50mV), many more Na+ channels open and there is an influx of Na+. REPOLARISATION- when the inner membrane has an action potential of +40mV, this causes voltage gates Na+ channels to close and voltage gates K+ channels to open. HYPERPOLARISATION- K+ effluxes out of the cell, however there is an overshoot of K+ ions since K+ channels are slow to close. Once the K+ channels eventually close, the ionic concentrations inside and outside of the cell can be reset to the resting membrane potential RESTING POTENTIAL- both K+ and Na+ channels are closed. A Na+/K+ pump uses ATP to reestablish the resting potential. ( will draw the diagram of an action potential)
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