# What is the human brain?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 10 Aug 2026, 13 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19590498-what-is-the-human-brain.mp3

Did you know there is a supercomputer inside your head that runs on less power than a tiny refrigerator lightbulb? It’s true! Your brain is a squishy, grey blob that weighs about three pounds—exactly like a small cantaloupe—but it controls absolutely everything you do! Join Mira and Finn on Science is Not Boring as they uncover the wild secrets of the most complex machine in the known universe. Discover how a scientist made "brain soup" to count an amazing 86 billion tiny cells called neurons! We'll learn how these biological wires shoot electrical sparks at mind-blowing speeds of 270 miles per hour, which is faster than a Formula One race car! Find out why your amygdala (which totally sounds like a dinosaur!) makes your stomach drop on a rollercoaster, and why going to sleep is literally just taking out the brain trash in a magical nightly biological car wash. Your brain even has more connections than there are stars in the entire Milky Way galaxy! So get ready to stretch those neurons and build your brain city in this super-charged, fact-filled episode!

## Transcript

[0:46] SPEAKER_00: Welcome to Science Is Not Boring by Kidopoly.com.
[0:50] SPEAKER_00: I'm Mira! And I'm Finn.
[0:53] SPEAKER_00: Did you know your entire body is being controlled right this very second by a squishy, wrinkly blob that runs on less power than the tiny light bulb inside your refrigerator?
[1:05] SPEAKER_01: Wait, what?
[1:06] SPEAKER_01: A fridge light bulb?
[1:08] SPEAKER_01: That's definitely not enough power to make me run, jump, and play all day.
[1:13] SPEAKER_00: Well, believe it or not, this£3 blob is widely considered the most complex machine in the known universe.
[1:21] SPEAKER_00: Today, we are talking about your amazing brain.
[1:25] SPEAKER_01: Oh, the brain! So squishy! And it sits up there in the dark inside our skulls, just pulling all the strings like a master puppeteer.
[1:34] SPEAKER_00: Exactly! Squishy, grey, and about the size of your two fists pushed together.
[1:40] SPEAKER_00: Your brain runs absolutely everything you do, and it never, ever takes a single break.
[1:46] SPEAKER_00: Not even when I'm sleeping.
[1:48] SPEAKER_00: Especially when you're sleeping.
[1:51] SPEAKER_00: Today we're going to find out how billions of tiny cells pass messages using electricity.
[1:57] SPEAKER_00: What really happens when you feel terrified or thrilled, and why your brain literally washes itself while you snooze.
[2:09] SPEAKER_01: That sounds super gross.
[2:12] SPEAKER_00: Not quite soap, but we'll get there.
[2:15] SPEAKER_00: First, let's look at what this incredible biological machine is actually made of.
[2:20] SPEAKER_00: So, if you were to hold a human brain in your hands, it would feel incredibly soft, kind of like a firm jelly, and it would weigh about three pounds.
[2:30] SPEAKER_01: Three pounds?
[2:32] SPEAKER_01: That's exactly like the weight of a small cantaloupe.
[2:35] SPEAKER_00: Great comparison! And even though it only makes up about 2% of your total body weight, it demands a massive 20% of your body's oxygen and blood flow.
[2:47] SPEAKER_00: It is the absolute boss.
[2:49] SPEAKER_01: But what's actually inside it?
[2:51] SPEAKER_01: Is it just one big wrinkly muscle?
[2:54] SPEAKER_00: Nope, the brain isn't a muscle at all.
[2:57] SPEAKER_00: It's made of about 60% fat, a lot of water, and a massive dense network of special cells called neurons.
[3:05] SPEAKER_01: Neurons?
[3:06] SPEAKER_01: Are those like tiny little biological wires?
[3:10] SPEAKER_00: Exactly like wires.
[3:12] SPEAKER_00: For decades, scientists guessed there were about a hundred billion of them in the human brain.
[3:18] SPEAKER_00: But a brilliant scientist named Dr.
[3:20] SPEAKER_00: Susanna Herculano Hausell wanted to find the exact number.
[3:25] SPEAKER_00: How do you even count that high?
[3:28] SPEAKER_01: It would take hundreds of years just to count to a billion.
[3:31] SPEAKER_00: She actually invented a special new technique.
[3:35] SPEAKER_00: She dissolved brain tissue into a liquid soup so she could easily count the cell nuclei under a microscope.
[3:42] SPEAKER_01: Ew, brain soup! That is totally gross.
[3:46] SPEAKER_01: Imagine seeing that in a laboratory.
[3:49] SPEAKER_00: It sounds a little wild, but it completely changed neuroscience.
[3:54] SPEAKER_00: In 2009, she proved that the average human brain actually has 86 billion neurons.
[4:07] SPEAKER_00: Way, way more! There are about 8 billion people on Earth.
[4:12] SPEAKER_00: Having 86 billion neurons is like packing more than 10 entire Earth populations right inside your skull.
[4:20] SPEAKER_01: Okay, my head feels heavy just thinking about it.
[4:23] SPEAKER_01: What do all these 86 billion microscopic cells actually do all day?
[4:28] SPEAKER_00: They talk to each other.
[4:30] SPEAKER_00: They constantly pass messages back and forth to tell your heart to beat, your lungs to breathe, your stomach to digest, and your hand to move.
[4:39] SPEAKER_00: Wait, how do they talk to each other?
[4:41] SPEAKER_00: Do they have tiny little mouths?
[4:44] SPEAKER_00: No mouths.
[4:46] SPEAKER_00: They communicate using electricity and chemicals.
[4:49] SPEAKER_00: Whenever you want to do something, like wiggle your big toe, a neuron in your brain fires a tiny electrical spark.
[4:57] SPEAKER_00: A spark?
[4:58] SPEAKER_01: Like actual electricity inside my head.
[5:01] SPEAKER_00: Yes! That electrical spark travels down the neuron's tail, which is called an axon.
[5:07] SPEAKER_00: And these cells can be super long.
[5:09] SPEAKER_00: Some neurons stretch all the way from the base of your brain down to your spinal cord.
[5:14] SPEAKER_00: One single microscopic cell that long?
[5:18] SPEAKER_00: That's wild.
[5:19] SPEAKER_00: And the speed they travel is absolutely mind-blowing.
[5:23] SPEAKER_00: These electrical nerve signals can race through your body at up to 270 miles per hour.
[5:29] SPEAKER_01: 270 miles per hour?
[5:32] SPEAKER_01: That's faster than a Formula One race car.
[5:35] SPEAKER_00: It is! That's exactly why when you stub your toe, you feel the initial bump almost instantly, before the pain even hits.
[5:43] SPEAKER_00: The touch signal rockets from your toe, races up your leg and spine, and hits your brain in about 0.02 seconds.
[5:51] SPEAKER_01: Wow! So with 86 billion cells zapping electricity at race car speeds all day, my head must need tons of power.
[5:59] SPEAKER_01: Like, I should probably walk around with a giant battery.
[6:03] SPEAKER_00: That is the craziest part about human biology, Finn.
[6:07] SPEAKER_00: The world's fastest, most advanced supercomputers need up to 20 million watts of power to run.
[6:14] SPEAKER_01: Okay, so what does my brain need?
[6:16] SPEAKER_01: A billion watts?
[6:18] SPEAKER_01: Try 20 watts.
[6:19] SPEAKER_01: Wait, just 20 watts?
[6:22] SPEAKER_01: Like the tiny dim light bulb in my refrigerator.
[6:25] SPEAKER_00: Exactly! Your brain is one million times more energy efficient than a supercomputer.
[6:31] SPEAKER_00: It runs your whole life, stores all your memories, and solves tough math problems, all on the energy of a fridge light bulb.
[6:39] SPEAKER_01: That is the coolest thing I've ever heard.
[6:41] SPEAKER_01: It's like having a superpower.
[6:43] SPEAKER_01: But what about when I get super scared or really happy?
[6:47] SPEAKER_01: Like when I ride a giant roller coaster and my stomach does flips.
[6:51] SPEAKER_01: Is that electricity too?
[6:52] SPEAKER_00: Yes, but it also triggers chemicals.
[6:55] SPEAKER_00: Deep inside the centre of your brain is a tiny, almond-shaped cluster of neurons called the amygdala.
[7:02] SPEAKER_01: Haha, the amygdala! That sounds like a dinosaur name.
[7:07] SPEAKER_00: It really does.
[7:09] SPEAKER_00: But it's actually the part of your brain that handles strong emotions, like fear, anger, and excitement.
[7:15] SPEAKER_00: When you drop down that steep roller coaster track, your amygdala instantly floods your brain with chemicals.
[7:21] SPEAKER_00: Is that why my heart beats super fast and my hands get sweaty?
[7:25] SPEAKER_00: Exactly.
[7:26] SPEAKER_00: It's a completely automatic reaction to keep you safe.
[7:30] SPEAKER_00: But the brain doesn't just work hard when you're awake and screaming on roller coasters.
[7:35] SPEAKER_00: It does some of its most important work when you are fast asleep.
[7:39] SPEAKER_01: But doesn't the brain go to sleep too?
[7:41] SPEAKER_01: Like powering down for the night to rest?
[7:44] SPEAKER_00: Not at all.
[7:45] SPEAKER_00: While your body rests, your brain actually goes into active cleaning mode.
[7:50] SPEAKER_00: It uses something called the gymphatic system.
[7:53] SPEAKER_00: The gymphatic system?
[7:55] SPEAKER_00: What is that?
[7:56] SPEAKER_00: Well, in 2012, scientists discovered that during deep, slow wave sleep, your brain cells actually shrink, which causes the microscopic spaces between them to widen.
[8:07] SPEAKER_00: Why would they change size like that?
[8:10] SPEAKER_00: So that a special clear liquid called cerebrospinal fluid can rush in, acting like a giant biological washing machine to flush out all the waste and toxins that built up during the day.
[8:22] SPEAKER_01: Whoa, so my brain literally gets a car wash every single night.
[8:26] SPEAKER_00: Yes, it washes away the cellular garbage, draining it down into your body's systems to be safely thrown away.
[8:33] SPEAKER_00: If you don't get enough sleep, that trash builds up, which is exactly why you feel so foggy and grumpy when you're tired.
[8:40] SPEAKER_01: So sleeping is literally just taking out the brain trash.
[8:44] SPEAKER_01: I'll definitely remember that the next time Mum tells me it's bedtime.
[8:48] SPEAKER_00: This matters so much, Finn.
[8:50] SPEAKER_00: Because understanding the brain helps doctors figure out how to keep it healthy as we get older, how we learn new skills, and even how to build better computers modelled after human efficiency.
[9:01] SPEAKER_01: Yeah, if we could make a giant computer run on just 20 watts of power, that would save so much electricity for the whole planet.
[9:09] SPEAKER_00: Exactly.
[9:10] SPEAKER_00: And the sheer scale of the brain is just unbelievable.
[9:14] SPEAKER_00: We talked about those 86 billion neurons earlier, right?
[9:18] SPEAKER_01: Yeah, the 10 Earth's worth of cells packed into my head.
[9:22] SPEAKER_00: Well, they don't just sit there.
[9:24] SPEAKER_00: They connect to each other at special meeting points called synapses.
[9:28] SPEAKER_00: And every single neuron can have up to 10,000 connections to other nearby neurons.
[9:34] SPEAKER_01: Wait, let me do the math.
[9:36] SPEAKER_01: 86 billion multiplied by 10,000?
[9:40] SPEAKER_01: Okay, my brain literally hurts just trying to calculate that.
[9:44] unknown: Haha!
[9:45] SPEAKER_00: I'll help you out.
[9:46] SPEAKER_00: It means there are up to 860 trillion synapses in a single human brain.
[9:52] SPEAKER_00: 860 trillion?
[9:54] SPEAKER_00: Is that even a real number?
[9:56] SPEAKER_00: It is.
[9:57] SPEAKER_00: That's 860 with 12 zeros behind it.
[10:01] SPEAKER_00: There are significantly more connections in your brain than there are stars in the entire Milky Way galaxy.
[10:07] SPEAKER_01: So I literally have a whole galaxy of connections inside my head.
[10:11] SPEAKER_01: That makes me feel kind of like an absolute superhero.
[10:15] SPEAKER_00: You are.
[10:16] SPEAKER_00: And the best part is called neuroplasticity.
[10:19] SPEAKER_00: Every time you learn something new, like playing a video game, riding a bike, or reading a book, your brain physically changes.
[10:27] SPEAKER_00: It builds brand new connections, just like laying down new roads in a growing city.
[10:32] SPEAKER_01: That is mind-blowing.
[10:34] SPEAKER_01: Literally, the more I learn, the bigger my city gets.
[10:38] SPEAKER_00: You got it.
[10:39] SPEAKER_00: And scientists are still discovering new things about it every single day.
[10:43] SPEAKER_00: The human brain really is the final frontier of biology.
[10:46] SPEAKER_00: Alright, Finn, it's time for the quiz.
[10:49] SPEAKER_00: Are you ready?
[10:50] SPEAKER_01: Oh man, a whole galaxy in my head.
[10:52] SPEAKER_01: I hope I can remember.
[10:54] SPEAKER_01: I'm ready! First question.
[10:56] SPEAKER_00: How much does the average adult human brain weigh?
[11:03] SPEAKER_00: Next one.
[11:05] SPEAKER_00: How many neurons did Dr.
[11:06] SPEAKER_00: Susanna Herculano Husel discover are in the human brain?
[11:14] SPEAKER_00: Question three.
[11:16] SPEAKER_00: How fast can electrical signals travel through your neurons?
[11:23] SPEAKER_00: Here's number four.
[11:25] SPEAKER_00: How many watts of energy does your brain use?
[11:32] SPEAKER_00: Last question.
[11:33] SPEAKER_00: What is the clear liquid that washes the brain's waste away during sleep?
[11:41] SPEAKER_00: Great job! Let's see how you did.
[11:44] SPEAKER_00: The first answer is the brain weighs about three pounds.
[11:49] SPEAKER_00: For question two, there are about 86 billion neurons.
[11:54] SPEAKER_00: Number three, the answer is signals can travel up to 270 miles per hour.
[12:02] SPEAKER_00: Question four, it uses just 20 watts, like a dim light bulb.
[12:07] SPEAKER_00: And the final answer is cerebrospinal fluid washes the brain.
[12:12] SPEAKER_01: Wow, I got most of those.
[12:14] SPEAKER_01: The 270 miles per hour one still totally blows my mind.
[12:18] SPEAKER_00: I know, right?
[12:19] SPEAKER_00: Your body is an absolute wonderland of science.
[12:23] SPEAKER_00: It's completely incredible to think that the very brain we use to learn about the brain today is sitting right inside our own heads.
[12:31] SPEAKER_01: Haha, talk about a massive brain twister.
[12:34] SPEAKER_00: If you had fun learning about how amazing your squishy grey brain is, please leave us a five-star review.
[12:40] SPEAKER_00: Just scroll down on your podcast app and tap the stars.
[12:44] SPEAKER_01: Yeah, give those 86 billion neurons a workout by giving us five stars.
[12:49] SPEAKER_00: Oh, and don't forget to check out our site kidopoly.com.
[12:53] SPEAKER_00: We've got tons of fun learning games and activities waiting for you there.
[12:57] SPEAKER_01: And if you want to shout out on the show or just want to say hi, send us an email at hello at kidopoly.com.
[13:05] SPEAKER_00: See you next time on Science Is Not Boring.
[13:08] SPEAKER_00: Bye everyone!

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