Q.What do grey and white matter in the brain represent?

Think of the brain as the control room of a large building. Cameras and sensors send in information from every corner, someone in the control room decides what to do, and instructions go back out to switch things on or off. The brain plays exactly this role for the body: it is the central information-processing organ, the command and control system where incoming signals are understood and from which orders flow out.

Almost everything the body does is coordinated here. The brain directs voluntary movements, keeps the body balanced, and keeps vital involuntary organs such as the lungs, heart and kidneys working. It holds body temperature steady (thermoregulation), controls hunger and thirst, and manages the roughly twenty-four-hour rhythms of activity known as circadian rhythms. It also governs several endocrine glands and shapes behaviour. On top of these, the brain is where vision, hearing and speech are processed, and where memory, intelligence, emotions and thoughts arise.

Because an organ this important cannot be left exposed, it is very well protected:

• It sits inside the bony skull, which guards it against mechanical injury. …