<P> Action potentials are generated by special types of voltage - gated ion channels embedded in a cell 's plasma membrane . These channels are shut when the membrane potential is near the ( negative ) resting potential of the cell , but they rapidly begin to open if the membrane increases to a precisely defined threshold voltage , depolarising the transmembrane potential . When the channels open , they allow an inward flow of sodium ions , which changes the electrochemical gradient , which in turn produces a further rise in the membrane potential . This then causes more channels to open , producing a greater electric current across the cell membrane , and so on . The process proceeds explosively until all of the available ion channels are open , resulting in a large upswing in the membrane potential . The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse , and the ion channels then rapidly inactivate . As the sodium channels close , sodium ions can no longer enter the neuron , and then they are actively transported back out of the plasma membrane . Potassium channels are then activated , and there is an outward current of potassium ions , returning the electrochemical gradient to the resting state . After an action potential has occurred , there is a transient negative shift , called the afterhyperpolarization . </P>
<P> Action potentials are generated by special types of voltage - gated ion channels embedded in a cell 's plasma membrane . These channels are shut when the membrane potential is near the ( negative ) resting potential of the cell , but they rapidly begin to open if the membrane increases to a precisely defined threshold voltage , depolarising the transmembrane potential . When the channels open , they allow an inward flow of sodium ions , which changes the electrochemical gradient , which in turn produces a further rise in the membrane potential . This then causes more channels to open , producing a greater electric current across the cell membrane , and so on . The process proceeds explosively until all of the available ion channels are open , resulting in a large upswing in the membrane potential . The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse , and the ion channels then rapidly inactivate . As the sodium channels close , sodium ions can no longer enter the neuron , and then they are actively transported back out of the plasma membrane . Potassium channels are then activated , and there is an outward current of potassium ions , returning the electrochemical gradient to the resting state . After an action potential has occurred , there is a transient negative shift , called the afterhyperpolarization . </P>
where are action potentials generated in a neuron
where are action potentials generated in a neuron
in a cell 's plasma membrane
in a cell 's plasma membrane