The inside of the cell membrane becomes negative at the time of an action potential.
Question
The inside of the cell membrane becomes negative at the time of an action potential.
Solution
Yes, that's correct. During an action potential, the inside of the cell membrane does become negative. This is due to the movement of ions across the membrane. Here's a step-by-step explanation:
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At rest, the inside of the neuron is negative relative to the outside. This is due to the distribution of different ions inside and outside the cell, and the selective permeability of the cell membrane.
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When an action potential is triggered, voltage-gated sodium channels open. Sodium ions, which are more concentrated outside the cell, rush into the cell due to the concentration gradient.
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The influx of positive sodium ions makes the inside of the cell temporarily more positive than the outside. This is the "depolarization" phase of the action potential.
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Shortly after the sodium channels open, they close and voltage-gated potassium channels open. Potassium ions, which are more concentrated inside the cell, rush out of the cell due to the concentration gradient.
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The efflux of positive potassium ions makes the inside of the cell more negative again. This is the "repolarization" phase of the action potential.
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The potassium channels close a bit slower, causing a brief "hyperpolarization" phase where the inside of the cell is even more negative than at rest.
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Finally, the sodium-potassium pump works to restore the original distribution of ions, returning the neuron to its resting state and readying it for the next action potential.
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Complete the sentences describing the events that occur during an action potential.An action potential will not occur unless the membrane potential at the (the initial segment of the axon) reaches a level called .When threshold is reached, of the initial segment open briefly, allowing to diffuse into the cell.As these ions enter the cell, the cell membrane undergoes , with the membrane potential increasing to a peak of approximately +30mV.As the peak of the action potential is reached, the sodium channels close and the open, allowing these ions to diffuse out of the cell.As cations leave the cell, the membrane potential at that part of the membrane once again becomes negative. This phase of the action potential is called , because the resting membrane potential is being reestablished.The membrane potential actually dips lower than -70mV because the potassium channels do not close quickly enough. This phase is called .
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