What happens if you hit your head? If the skull is broken, the pieces of broken bone may dig into the brain and tear the very delicate brain tissue. Hospital attention is always required.   Even if your skull is not broken, it's possible to sustain serious brain damage. This happens if the brain impacts onto the inside of the skull, or twists against its rough surface.

Sometimes this causes bruising or bleeding. Bleeding is particularly dangerous as the brain can get squashed against the inside of the skull, causing further damage. A person with this type of injury may seem fine initially, but must be kept under observation as the life-threatening effects take several hours to reveal themselves.

So what does your brain look like?

Is your brain in two halves?
Yes, the outer part of your brain called the cortex is split in two - making your left and right hemispheres. They are connected by a bundle of 50 million neurons

Why does your brain feel tired when you think a lot? Your brain consumes a lot of energy - as much as a fifth of all the energy you get from food. Brain scans show that thinking uses up a lot of energy (as revealed by increased blood flow). Your brain can't store much energy, and because it is tightly enclosed inside your skull, there is a limit to how much blood (and therefore energy) can be supplied to active areas. So thinking hard tires your brain.

So is your brain like a muscle?
New research shows that, as with muscles, the more you use a part of your brain, the larger it will get. London taxi drivers have very large hippocampi - the part of the brain that deals with spatial mapping.

Also like muscles, as you use a particular part of your brain, more blood is pumped to that area to provide energy. Finally, as with muscles, the more you use your brain, the better it works.