What does the brain do?

Your brain weighs about 1.4 kilograms, a little more than a bag of sugar. It is soft and wrinkly, and it sits safely inside your skull. It is made of billions of tiny cells called neurons, about 86 billion of them. Neurons send electrical signals to each other along pathways. Your brain uses about a fifth of the energy your body uses, even though it is a small part of your weight.

The brain has three main parts:

• Cerebrum: the largest part, split into a left and right half. It handles thinking, memory, speech and understanding what you see, hear and feel. It also controls the movements you choose to make.
• Cerebellum: at the back, below the cerebrum. It helps with balance and smooth movement, so you can ride a bike or catch a ball.
• Brainstem: it connects the brain to the spinal cord and controls things you do without thinking, like breathing and your heartbeat.

The brain talks to the rest of the body through the nervous system. The spinal cord, inside your backbone, and the nerves branching out from it work like cables. Messages from your senses travel to the brain, and its instructions travel back to your muscles.

Your brain is always changing. Each time you practise something, such as a times table or a song, connections between neurons get stronger. This is why practice works and why mistakes are useful; see growth mindset. Sleep helps the brain store what you have learned. You can look after it by sleeping well, eating healthy food, staying active, and wearing a helmet when you cycle.

The idea that we only use 10 percent of our brains is a myth. We use all of it, although not every part at the same moment.