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Neuron Action Potential Sequence of Events

  • At rest, the axon membrane is slightly image descriptionpolarized to about -70mV, image descriptionmeaning the intracellular fluid (ICF) is relatively negative to the extracellular fluid (ECF).
An image showing the Neuron Action Potential Sequence of Events, the neuron axon membrane is enlarged and contains different channels
An image showing the polarized potential plot of the neuron axon membrane at rest, the neuron axon membrane is enlarged and contains different channels
An image showing the charge of the outside and inside the neuron membrane potential, the neuron axon membrane is enlarged and contains different channels
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  • An action potential occurs when a portion of the membrane rapidly depolarizes and then repolarizes again to the original resting state.
  • The process is initiated by a threshold level image descriptionstimulus, such as a nearby image descriptionchange in membrane potential (threshold potential, local potential).
An image showing the charge of the outside and inside the neuron membrane potential, the neuron axon membrane is enlarged and contains different channels
An image showing the stimulus of the axon neuron membrane to initiate the process, the neuron axon membrane is enlarged and contains different channels
An image showing the change in the neuron membrane potential after stimulation, the neuron axon membrane is enlarged and contains different channels
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  • Na+ ions entering the cell make the membrane potential less negative. More Na+ channels open as result and a cycle of image descriptiondepolarization develops.
An image showing the change in the neuron membrane potential after stimulation, the neuron axon membrane is enlarged and contains different channels
An image showing the depolarization plot after Na+ channels opening, the neuron axon membrane is enlarged and contains different channels
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  • When the membrane potential reaches about +30mV (reverse polarization), the timed image descriptionNa+ channels close due to inactivation and the Na+ influx stops.
An image showing the depolarization plot after Na+ channels opening, the neuron axon membrane is enlarged and contains different channels
An image showing the repolarization plot after K+ ions diffuse out, the neuron axon membrane is enlarged and contains different channels
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  • The K+ channels are slow to close, so the membrane briefly hyperpolarizes.
  • As the K+ channels close, Na+/K+ image descriptionpumps actively transport Na+ ions out of the cell and K+ ions into the cell.
  • The ion exchange helps image descriptionre-establish the ion diffusion gradients and resting membrane potential.
An image showing the repolarization plot after K+ ions diffuse out, the neuron axon membrane is enlarged and contains different channels
An image showing the Membrane potential re-establishment plot after pumps actively transport, the neuron axon membrane is enlarged and contains different channels
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