Читать книгу Neurobiology For Dummies - Frank Amthor - Страница 109

The sudden opening and then closing of many voltage-dependent sodium channels produces an action potential, or spike — sharp voltage change across the cell’s membrane.

If you do a computer simulation of the action of voltage-dependent sodium channels using their known kinetics, the simulated action potential lasts longer than actual spikes in most real neurons. The reason is that voltage-dependent potassium channels also exist, and they’re almost always near voltage-dependent sodium channels. (They also open when the neuron is depolarized, but more slowly than the sodium channels.) When these voltage-dependent potassium channels open, potassium flows out of the cell, which drives the membrane potential toward the potassium equilibrium potential around –75 mV. This shortens the duration of the action potential because opening potassium channels repolarizes the cell more rapidly than closing the voltage-dependent sodium channels.