How Your Brain Works

What happens

• Your brain has about 86 billion neurons and about as many support cells, called glia.
• Neurons signal with electrical impulses along their axons and chemical messengers across tiny gaps called synapses.
• Each part of the brain has its own jobs, and the left side of the brain controls the right side of the body.
• The brain keeps rewiring as you learn, at any age. This is called plasticity.
• It is only about 2% of your body weight but uses about a fifth of your body's oxygen.

Know the warning signs

• Becoming very drowsy or confused after a knock to the head
• Vomiting again and again after a head injury
• A headache that gets worse after a head injury

If someone shows any of these signs after a knock to the head, call 9-1-1 or your local emergency number.

Call 9-1-1 or your local emergency number.

What you can do

• Keep your blood pressure, blood sugar and cholesterol in check, and don't smoke.
• Stay active. Brisk walking a few times a week helps your brain as well as your heart.
• Aim for seven or more hours of sleep a night.
• Stay connected with people and keep learning new things.
• Look after your hearing: get it checked, and use hearing aids if you need them.
• Protect your head: wear a helmet to cycle, ski or skate, and always buckle up.

Common questions

Do we really only use 10% of our brain?

No. Brain scans show activity all across the brain, and damage to almost any part of it causes problems. Different areas are busier at different moments, but over a day you use virtually all of your brain.

Can adults grow new brain connections?

Yes. Every time you learn something, connections between neurons get stronger and new ones form. This is called plasticity, and it continues throughout life. In studies, adults in their twenties and people around sixty who learned to juggle showed brain changes on scans after about three months.

Can dementia be prevented?

Not always, but the risk can often be lowered. A 2024 Lancet Commission report estimated that nearly half of dementia cases worldwide could, in theory, be prevented or delayed by tackling 14 risk factors, including high blood pressure, diabetes, high cholesterol, smoking, physical inactivity, hearing loss, social isolation and head injury.

Transcript

Right now, as you watch this, billions of nerve cells in your head are sending signals to one another. Together, they make you who you are.

Your brain weighs only about three pounds. Yet it runs everything you think, feel and do. Let's see how your brain works, and how to keep it healthy.

Those nerve cells are called neurons. One careful count put the number at about eighty-six billion. And they have partners: about as many support cells, called glia, that feed, protect and clean up after them.

A neuron has a cell body, short branches that pick up signals, and one long wire, called the axon, that sends signals on.

When a neuron fires, a tiny electrical impulse races along the axon. A fatty coating called myelin helps it travel fast.

At the end, there's a tiny gap before the next neuron, called a synapse. The signal can't jump it. Instead, the neuron releases chemical messengers, which cross the gap and pass the message on.

Each neuron can connect with thousands of others. That adds up to trillions of connections, all working at once.

Now let's zoom out. The largest part of your brain is the cerebrum, with its wrinkled surface. It's split into two halves, and each half has four main lobes.

At the front, the frontal lobe helps you plan, make decisions and move. Behind it, the parietal lobe handles touch, and senses where your body is.

Along the sides, the temporal lobes help with hearing and memory. And at the back, the occipital lobe makes sense of what you see.

Tucked underneath, at the back, is the cerebellum. It keeps you balanced, and makes your movements smooth.

And the brainstem links your brain to your spinal cord. It runs things you never have to think about: your breathing, your heart rate, and when you sleep and wake.

Here's a surprise. The left side of your brain controls the right side of your body, and the right side controls the left. That's why a stroke on one side of the brain can weaken the opposite side of the body.

Your brain also changes. Every time you learn something, connections between neurons grow stronger, and new ones form. This is called plasticity.

And it keeps happening your whole life. When adults, including people around sixty, learned to juggle, brain scans showed changes after just three months.

Something this precious is well protected. There's the hard skull, then three thin layers called the meninges, and a clear fluid that cushions the brain, so it floats inside your head.

It's also hungry. Your brain makes up only about two percent of your body weight, yet it uses about a fifth of all the oxygen your body takes in.

So how do you look after it? A major 2024 report found that nearly half of dementia cases could, in theory, be prevented or delayed, by tackling fourteen risk factors we can change.

What's good for your heart and blood vessels is good for your brain. So keep your blood pressure, blood sugar and cholesterol in check, and don't smoke.

Keep moving. In one study, older adults who walked briskly three times a week grew their hippocampus, a key memory area, by about two percent in a year.

Sleep matters too. While you sleep, your brain sorts and stores what you learned during the day. Most adults need seven or more hours a night.

Stay connected with people, and keep learning new things. And look after your hearing. Hearing loss is one of the biggest risk factors of all, so get it checked, and use hearing aids if you need them.

And protect your head. Wear a helmet to cycle, ski or skate, and always buckle up. After a knock to the head, if someone gets very drowsy or confused, keeps vomiting, or has a headache that gets worse, call 9-1-1 or your local emergency number.

One common myth is that we only use ten percent of our brain. In fact, scans show activity all across the brain, and damage to almost any part causes problems. Over a day, you use virtually all of it.

So, to recap. Neurons talk with electrical and chemical signals. Each part of the brain has its own jobs. It rewires as you learn. And healthy habits help protect it.

Now you know how your brain works, and how to look after it. It's been busy the whole time you were watching.

Sources

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