 We wanted to show you the dominoes analogy that we use in the neuron module. This is a domino. Dominoes is a game that you use by matching up the numbers with other dominoes. So these dominoes are on this neuron that we've pictured here on the table for you. So you see the cell body all the way down to the axon terminals. And these represent sodium channels that are along the membrane. So as a signal comes in here, coming in the dendrite, it's going to open sodium channels. If the signal is strong enough, that opening that sodium channel will open all of the rest of the sodium channels next to it and it will automatically keep the signal going where it cannot stop all the way down to the axon terminals. So just like these dominoes are here, the signal comes in and it's a strong enough signal. It's going to open a sodium channel and again those sodium channels will open all the way down the axon and not stop. So here comes our signal and it won't stop all the way down. As you saw in the previous video, we had a signal come in that was strong enough to open sodium channels all the way down creating an action potential that would carry the signal to the axon terminals and the next neuron. If a signal comes in though that is not strong enough to open all of the sodium channels, that signal will only open sodium channels in a localized area. That signal would fizzle out and it would not create the action potential all the way down the axon. So if a signal came in the dendrites that was not strong enough, then it would be what we call a graded potential. A graded potential is a localized potential that fizzles out. It must be added to other graded potentials enough to cause the action potential to go all the way down the axon. If enough of those had come together in this area called the axon hillock, then that would have been enough to have caused the signal to go all the way down the neuron. If it's not enough, it's called a graded potential or a localized potential. What's an example of that? Well, think about if you had a mosquito crawling on your arm or your hand and you didn't notice it. That would be like the graded potential. There's something there, but it's not enough to send the signal all the way up to the brain. If you were stung by that mosquito, though, that might be enough of a signal to send that message all the way up to the brain that, ouch, you were stung. So again, this was an example of a graded potential that fizzles out, not strong enough to create the action potential.