COMMUNICATION AMONG NEURONS
There’s no question that the main signaling within the body is done by the neurons. But how do these cells perform their function? In tackling this crucial question, we’ll proceed in three steps: First, we’ll look at the functioning of individual neurons and ask what it is about these cells that allows them to “respond”—i.e., to change their functioning in response to stimulation. We’ll also consider how the response is transmitted within the neuron—usually from the dendrites (where the input signal first arrives) to the axon and then down the length of the axon. Second, we’ll discuss how information travels between neurons—that is, from the axon’s ending to the next neuron in the chain. As we’ll see, communication within the neuron (i.e., from one end to the other) involves electrical signals; but communication between neurons (i.e., from one neuron to another) involves an entirely different system that relies on chemical signals. Third, we’ll then want to take a closer look at these chemical signals.Among other things, this step will allow us to ask how neurons differentiate between types of signals as well as how they manage to integrate information received frommany sources at once. This discussion also has a crucial implication because an understanding of this chemistry allows us to explain why many drugs work the way they do.