What Is the Role of Voltage-Gated Channels in the Course

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The Answer is When a neuron receives a signal from another neuron, the receiving neuron undergoes an abrupt change in membrane potential, which causes voltage-gated sodium channels to open at the base of the axon, where it emerges from the cell body. This in turn allows extracellular sodium ions (Na+) to flow into the axon. They move into the axon because the concentration of Na+ ions is much greater outside the membrane than inside. The influx of positively charged Na+ ions causes the membrane potential to become more positive. This change in membrane potential is called depolarization because the membrane potential is becoming less polarized-that is, less extreme, moving from −70 mV toward 0. If the depolarization surpasses a threshold at about −45 mV, the inflow of Na+ ions continues rapidly until the difference in electric charge at the inner and outer surfaces of the membrane is reversed, with the inside of the axon becoming more positively charged than the outside, resulting in a membrane potential of about +30 mV at its peak. Immediately after the sodium channels open, they close again, stemming the inflow of Na+ ions, and nearby potassium channels open (in response to the depolarization of the membrane), allowing positively charged potassium ions (K+) to flow out of the axon, again driven by the concentration difference. The outflow of K+ ions pushes the membrane potential back toward its resting value of −70 mV, a process called repolarization. Like the sodium channels, the potassium channels close again immediately after opening. The membrane potential briefly exceeds the resting potential-this is termed hyperpolarization-before returning to the resting potential.

What Is the Role of Voltage-Gated Channels in the Course

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