Everything happens through a neuron
Goodness, this diagram reminds me of the most boring part of school. Do we really need to know about this?
Yes. Every action we take, every decision we make, every thought we create, and every emotion we feel happens through a neuron. Neurons are so important we have almost a hundred billion of these in our brains. And each neuron is in turn connected (what we call a synapse) to a vast network of other neurons, numbering up to 10,000 - a quadrillion synapses in total. This is the most complicated network we know of, and it is wired right in our heads, and it is the reason why we are able to do what we do.
Neurobiology is not simple. And a large part of neurology is bloody boring. But don't worry - fortunately we get to cover the exciting bits. Let's get started.
The picture we have above is that of a typical neuron in our brains. There are only a few things we really need to know about the neuron.
Dendrites (The Ears): First, at the top of the diagram, we see what is labelled dendrites. These resemble tree roots that lead into the cell body. Dendrites act as the ears of the neuron, listening to what other neurons are saying, and feeding this information into the cell body. Remember, each neuron could have thousands of dendrites, with thousands of other neurons feeding information to it.
Axon and Axon Terminals (The Mouth): Leading out of the cell body, the axon is a tube-like structure. At its end, tentacle-like axon terminals. These axon terminals are the mouth of the neuron, communicating messages to other neurons by forming a synapse with a dendrite of the other neurons.
Nucleus (The Switch): The nucleus is where information of each neuron is stored. This includes basic biological information (for example, each nucleus carries your entire DNA code), as well as new information which you have picked up over time. The main characteristic for us to note here is that the nucleus has a threshold before it is willing to talk. In other words, it needs to be stimulated sufficiently before it is willing to talk. Think about the new person in the group who has to be warmed up before he starts adding to the conversation. However, if it is not sufficiently stimulated enough to speak, the nucleus keeps quiet. It is an "all or nothing" situation.
Myelin (The Accelerator): While the nucleus is grey in colour - giving rise to the phrase "grey matter in your head", myelin is white. Scan a brain, and you will notice it is a combination of white and grey. This shows how much myelin there is, stretching from groups of neurons to another. Myelin is a fatty sheath that wraps around the axon, which causes the signal from a neuron to fire faster.
Synapse (The communications channel)
Ranvier Node (For our purposes, who cares?): What's the node of a Ranvier? Good news - not important for our purpose. Don't waste your valuable neurons on this.