How are action potentials transmitted?

Information passes through nerves rapidly in the form of action potentials, or transient changes in voltage across the nerve cell membrane. Nerve cells, or neurons, are able to transmit action potentials thanks to specific ion channels in their membranes. At rest, the voltage across the membrane, or 'resting potential', is close to -70mV. At the start of an action potential, sodium channels in the membrane open, and positively charged sodium ions flow into the neuron, depolarising the membrane by driving the potential up to 30mV or higher. Slower-opening potassium channels allow potassium ions to flow out of the neuron, driven by the increase in charge inside due to the buildup of sodium. The efflux of potassium decreases membrane potential (hyperpolarises) to slightly below resting potential, reffered to as an 'overshoot'. Finally, resting potential is restored by the sodium-potassium pump, which uses energy from the breakdown of ATP to exchange sodium inside the cell for potassium outside. This sequence of events continues along the neuron axon as depolarisation of one segment causes sodium channels to open in the adjacent segment and the process to restart.

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