Resting Potential of a Neuron

Correct Answer: D. the concentration of sodium ions in the extracellular space is greater than the concentration of potassium ions inside the axon.

In a resting neuron, there is more potassium ions inside of the axon than outside in the extracellular space. Likewise there is more sodium in the extracellular space than inside of the axon. The difference in the concentrations of the ions results in a resting potential inside of the axon of -70mV (in humans). When the action potential occurs, sodium/potassium channels open, allowing the free movement of sodium ions into the axon and potassium ions out of the axon. This causes the axon to depolarize and become positive. After the action potential, the resting potential is restored using the sodium/potassium pumps.

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