The reason that psychologists need to know about the workings of the central nervous system is that most, if not all, of our psychological behaviour is underpinned by our physiological makeup (most notably the workings of our brains). Having analysed the neuron, we can now proceed by looking at the structure of our nervous system. In this chapter we will look at the central nervous system and in Chapter 4 we will look at the autonomic nervous system. You may be thinking, why not look at all of it together? Well, the central nervous system is the most important part of our nervous system (the central processing unit, for the computer literate) and is involved in all psychological activity, whereas the autonomic nervous system is a peripheral system and has a specialist function as far as psychological interest is concerned. They are separated here to emphasise their differential importance in biological psychology.