Introduction

Our body performs an enormous range of everyday functions without us consciously directing them: the eyes see, the ears hear, the heart beats on its own steady rhythm, air moves in and out of the lungs, and even something like tearing up when a limb is hurt happens automatically. Despite constant changes in the outside world, the body holds itself in a remarkably stable condition, with every one of its billions of cells working in step with the others. That coordination is the job of the neural system.

The neural system links and coordinates every other system in the body so they work together smoothly, carrying millions of signals every second - telling the heart when to beat, the kidney when to excrete waste, or triggering the sensation of taste when we eat. It can even manage several such jobs at once, which is why a person can play an instrument while singing, or hold a conversation while cycling - every coordinated action, skilled or routine, depends on this same integrating power. This chapter looks at how the neural system is organised, how it ties together every organ in the body, and what cellular events make that coordination possible.