00:00There are more connections in your brain than stars in the Milky Way.
00:03Three pounds of tissue, holding everything you've ever been.
00:08Let's go inside.
00:10Three pounds.
00:1173% water, soft as tofu, no pain receptors,
00:15yet it processes more information in 30 seconds than the Hubble telescope in 30 years.
00:2086 billion neurons.
00:22Each one has dendrites that receive signals and an axon that sends them.
00:26Wrapped in myelin insulation, signals travel at 200 miles per hour.
00:30Neurons don't touch.
00:31Between them, a tiny gap called the synapse.
00:33Chemical messengers float across, lock into receptors.
00:36The next neuron fires.
00:37100 trillion conversations.
00:40Opamine makes you feel reward.
00:41Serotonin keeps you calm.
00:43Glutamate says fire.
00:44Gaba says stop.
00:49A neuron fires by opening tiny gates.
00:52Sodium rushes in.
00:53Voltage spikes.
00:54The signal races down the axon at 268 miles per hour.
00:58One millisecond.
01:00The cortex is only two millimeters thick.
01:02But everything you think, say, imagine, and decide happens here.
01:07Evolution folded genius into a compact package.
01:10Four lobes.
01:11Frontal.
01:11Decisions and personality.
01:13Parietal.
01:13Touch and space.
01:14Temporal.
01:15Hearing and language.
01:16Occipital.
01:17Vision.
01:17Not in your eyes.
01:18In the back.
01:20In 1848, an iron rod went through Phineas Gage's frontal lobe.
01:24He survived, but became a different person.
01:27The frontal lobe holds your identity.
01:29You don't see with your eyes.
01:31They're just cameras.
01:32Your occipital lobe at the back of your head builds everything you see.
01:37The image arrives upside down.
01:40Your temporal lobe processes every sound you hear.
01:43It also understands language.
01:45Damage it, and you speak in fluent nonsense.
01:47Without ever knowing something is wrong.
01:49The brainstem controls everything you never think about.
01:52Breathing.
01:53Heartbeat.
01:54Swallowing.
01:55Reflexes.
01:55It runs on autopilot.
01:57Without it, instant death.
01:59The cerebellum, little brain, holds over 50 billion neurons.
02:03It coordinates every movement you make.
02:05Walk.
02:05Catch.
02:06Type.
02:06Balance.
02:07Silently.
02:08Perfectly.
02:09Without a thought.
02:10Deep inside your brain, the limbic system.
02:12Your emotional core, fear, love, anger, joy, all born here.
02:17Without it, you could think, but never feel.
02:20The amygdala, the size of an almond, triggers your fight-or-flight response in 12 milliseconds.
02:25Heart pounds.
02:26Muscles tense.
02:27It can't tell a tiger from a deadline.
02:29Patient H.M. had both hippocampi removed.
02:32He could never form a new memory again.
02:34Every day, every person, was brand new.
02:37An eternal present.
02:38Forever.
02:39Forever.
02:39Short-term memory holds 7 things for 30 seconds, like RAM.
02:43Long-term memory is unlimited, like a hard drive.
02:46You remember your first kiss.
02:48Not last Tuesday's lunch.
02:50Memories aren't stored in one place.
02:51They're patterns.
02:52Millions of neurons wired together through repeated firing.
02:56Neurons that fire together, wire together.
02:58Patterns become permanent.
03:00Sleep isn't rest.
03:01It's maintenance.
03:02Your brain replays memories, flushes out toxic waste, repairs neurons, and processes emotions.
03:07Skip it, and everything breaks down.
03:10During dreams, your visual cortex creates images.
03:13Your amygdala creates emotion.
03:14But your logic shuts off.
03:16That's why dreams feel real, but make no sense.
03:19Your brain rewires itself every day.
03:22Learn something new.
03:23New connections grow.
03:24Practice a skill.
03:25Those pathways strengthen.
03:27Your brain is not fixed.
03:29It adapts.
03:30Dopamine doesn't create pleasure.
03:31It creates wanting.
03:32Every notification, every like, every scroll.
03:34Dopamine, your ancient reward system, hijacked by modern technology.
03:38Every single day.
03:40Your brain has never seen light.
03:42Never heard sound.
03:43Never felt touch.
03:44It sits in darkness, interpreting only electrical signals.
03:47Your entire reality is a construction.
03:50The hypothalamus, the size of a peanut, controls your body temperature, hunger, thirst, sleep, and hormones.
03:56The smallest structure with the biggest job.
03:58Survival headquarters.
04:002% of your body weight, but 20% of your energy.
04:03Your brain burns glucose constantly.
04:06Stop the blood for 4 minutes.
04:08Brain damage begins.
04:10A baby's brain forms 1 million new connections every second.
04:13By age 3, twice as many as an adult.
04:15Then the brain prunes.
04:17The last part to finish, age 25.
04:19Pain isn't in your body.
04:21It's in your brain.
04:23Soldiers fight with broken bones feeling nothing.
04:26Amputees feel pain in limbs that no longer exist.
04:29We know how neurons fire.
04:32We don't know why it creates experience.
04:34Why it feels like something, to be you.
04:36Consciousness remains science's greatest unsolved mystery.
04:40Alzheimer's steals memory.
04:41Parkinson's steals movement.
04:43Depression steals joy.
04:44Stroke steals function in seconds.
04:46The brain is powerful but fragile.
04:48Protect it.
04:49It's irreplaceable.
04:4986 billion neurons.
04:52More connections than stars.
04:54Every thought, every memory, every dream happening right now inside you.
04:57You don't live in the universe.
04:58It lives in you.
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