Now then, we need to get closer, so we can focus on the interaction of individual nerve cells. This bundle of nerves looks pretty good, but we have to go deeper.
Zoom in and enhance.
You see that bit with the two branches come together? That little gap between the two dendrites there is the synapse. It looks like this:
It works like this:
(Oh for Pete's sake. It's a minute long, just watch it, you babies.)
Now here's what you need to know:
1. Neurotransmitters are chemicals which physically move from the end of one neuron, across the synapse, and enter into another one.
2. When something triggers a nerve to fire, the impulse travels as an electrical signal (called an action potential) down the first neuron until it reaches the end, once it reaches the end, the electrical signal causes the neurotransmitters to exit the first neuron, cross the synapse, and enter the next neuron on the line. Their arrival triggers the next neuron to fire and we're back to electrical signals again.
3. Unless you live in a Lovecraftian hellhole, you are most likely unfamiliar with things that merge and squish about. So it may be a bit strange to try to imagine how the neurotransmitters actually leave and enter cells. If this is the case, I suggest you take a bath and play with the bubbles and soap for about three hours.
To make an analogy. Let's say you've just been informed that you're little sister is about to be eaten by a bear. How you know this doesn't matter, maybe Stephen Colbert told you, in any case, you go rushing along the nearest road to go save her ass.
Not on his watch.
But lo! A meteorite, probably summoned by some dumb kid that didn't know what he was doing, has wiped out a massive section of the road, and there's no way you can bridge the gap! Luckily for you, your brother is on the other side of the gap, but since he's a little stoner, he hasn't noticed your arrival. How do you get his attention? You throw a rock at him, of course.
Thus enlightened to the severity of the situation, your brother takes off down the road to go save your mutual sibling.
Here, Stephen Colbert is whatever triggered the nerve to fire, you are the first electrical signal, the first section of the road is the first neuron, your brother is the second electrical signal, the second section of the road is the second neuron, and the rock is the neurotransmitter.
Got it? Good. Let's move on.