![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXpng7F2Wjk0FqHL6kSIKHIAZ3PYydXareXcD1OGY18Vatz4Tgvz-USpnERRqcx6UK37kbJuhkFr2ZoQrmo8EzPLjNMsfSLeprZQGpYkYBVdqIld1l5TB3AilX4dYGt_Pi_kJbUTusxUA/s400/Complete_neuron_cell_diagram_en.svg.png)
Neurons can respond to stimuli and conduct impulses because a membrane potential is established across the cell membrane. In other words, there is an unequal distribution of ions (charged atoms) on the two sides of a nerve cell membrane. This can be illustrated with a voltmeter:
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3ZKnJ-6XI7n0MrUEBAfOQl77EffFHIV1BOVcS6IUEbGzeL4z5QljpmMWC4GUsFOa_a4hgXVJPu0lRYueF8wjXzDJsQilvXfZTHQaN4JC2aws0cjeQD6C2cjmAonzLq7GpYzG2tS4elxA/s320/voltmeter.gif)
With one electrode placed inside a neuron and the other outside, the voltmeter is 'measuring' the difference in the distribution of ions on the inside versus the outside. And, in this example, the voltmeter reads -70 mV (mV = millivolts).
In other words, the inside of the neuron is slightly negative relative to the outside. This difference is referred to as the Resting Membrane Potential