SciShow Tangents - Heads

Starting point is 00:00:00 Hello and welcome to SciShow Tangents, a lightly competitive science knowledge showcase. I'm your host, Hank Green, and joining me this week, as always, is science expert, Sari Reilly. Hello. And also our resident everyman, Sam Schultz. That's me. You guys, I'm really excited to tell you about my new product. It's the Bored Pelican Yacht Club. It's a line of NFTs, and they are pelicans that are not enthusiastic unattractive but extraordinarily valuable and you know how i know that they're so valuable because you said so that's right i said so i said that they are a smart business plan that i know i'm really excited about it as members of uh the podcast you two actually get a board pelican for maybe, let's say, 95% off, which means they're only $5,000 a piece.

Starting point is 00:01:11 The listeners of this podcast can get them for 25% off, but you can do the math for how much money that's going to be. It's a lot. I need one. Okay, great. What color do you want its eye lasers to be? I would love it to have very pink eye lasers pink eye lasers okay yeah i would like neon green neon green do you want your board pelican to be

Starting point is 00:01:33 in a suit of armor or a sailor's outfit is that the only two choices yes sailor's outfit please how much extra would i have to pay for a mermaid costume for my board pelican you know a completely reasonable amount because this isn't an amount you're paying it's an investment in the future yeah when you sell that one it's gonna be worth so much money that it won't matter how much you spend now so it's gonna be a lot but it's just like it being in the stock market i think the fact that you even asked how much it would cost means you're not ready for it, Sari. Sorry. You're not ready. That's true. I gotta just demand it. No one else can take this art from me. It's mine. And it is a mermaid pelican and it does have neon green laser beams shooting out of its eyes. Is it though drinking a decaf Americano or

Starting point is 00:02:22 smoking a big old blunt? I was gonna say, if mine's or smoking a big old blunt i was gonna say if mine's not smoking a big old blunt then i'm not buying so obviously you could light the blunt with your eye lasers it would be oh yeah it's so big that you can you can just look at it just look at yeah while it's in your mouth yeah i don't know how blunts work. I don't know if I really even know what a blunt is. It's a way to smoke leaves. Yeah. I think it's a big, it's like leaves rolled in paper. Don't correct me.

Starting point is 00:02:56 That's all I think. You can make a blunt like right now by going outside, gathering some mushy leaves, rolling it in paper and being like, here I got it. Oh, God. outside gathering some mushy leaves rolling it in paper and being like here i got it oh god well every week here on sci-show tangents we get together to try to one-up amaze and delight each other with science facts while also trying to stay on topic our panelists are playing for glory and for hank bucks and for bored pelicans which will be awarding as we play and at the end of the episode one of them will be crowned the winner and you will get a fractional ownership of one bored pelican we said i had to set up a dow so and you'll get a fractional ownership of one board pelican. We had to set up a DAO so that you could get one 500th of the pelican.

Starting point is 00:03:31 Now there's real skin in the game. Yeah. Believe it or not, this is the 50th episode of the third season of SciShow Tangents. That means there's only three episodes, including this one, left until season four. So starting this episode, we're going to count down to our big season three finale, which will be, spoiler alert, all about butts. But until then, we're going to be exploring some less butt-like parts of the body, starting with the exact opposite of the butt, which we will introduce with this week's science poem from Sam. Gather round and I'll explain-ium the glory of the good old cranium.

Starting point is 00:04:06 A feature of most creatures' bodies that you couldn't call extraneous. Mouth and eyes are features fairly common when we're considering the noggin. But ears can be there and often hair. The possibilities are boggling. When you need to hear or see or scream, you can depend upon your being. Where it has holes, and these holes' goals are to help you with your daily routine. It's the opposite of your butt, that blessed brain-filled coconut. It helps you think and helps you chew.

Starting point is 00:04:34 What it can't do, I don't know what. From bee to mouse, giraffe and poodle, we all rely on our thinkin' noodle. The home of intentions and inventions, from the bicycle to apple strudel. And that is all my poem's been said, a poem for our beloved head. To it we owe a debt most a-deady, because without it, we'd be dead. A Deady Debt. This week's topic is heads. You know, at first I thought, we don't need to talk to sari about what heads are and now

Starting point is 00:05:07 a mere 10 seconds later i'm having a crisis about what heads are oh yep that was my thought too i was like oh this is uh biologists have got this and then i started looking into this and it was like biologists have not got this doesn't seem like they have anything ever. They didn't have birds of prey. I know what my head is. We know what our heads are. We know what a lot of mammals' heads are very clear. But then you start to get into invertebrates or animals where the body plan is less head-butt continuum.

Starting point is 00:05:43 And you're not sure where the head ends and the torso begins, et cetera. You don't have to have a head. No. Many of animals don't have heads. Jellyfish. Great example. Starfish don't have head, but worm have head. Yeah.

Starting point is 00:05:57 Worms have head, yeah. And I feel like once you put eyes on it, I'm like, that's a head now. But mouth doesn't count as head. Just mouth on its own. So like a sea anemone, not a head. No. Just a hole. Do worms have eyes?

Starting point is 00:06:10 Sometimes. Sometimes. Okay. But I feel like the only reason a worm has a head if it doesn't have eyes, it's just because its body is long. Whereas a starfish has a mouth and it has a butt and they're on different sides of its body. So then it's just a really short tube. And then you should be able to say that a starfish has a mouth and it has a butt and they're on different sides of its body. So then like it's just a really short tube. And then you should be able to say that a starfish has a head.

Starting point is 00:06:29 But it definitely doesn't. Okay. Well, interesting. The point of head that I'm getting to is that it's like a concentrated node of things. So particularly nerves. So like nervous tissues like the brain and humans and many other mammals. So like nervous tissues, like the brain and humans and many other mammals. But if in organisms like a jellyfish, it's more of like a nerve net, like really distributed. But as soon as it gets kind of more concentrated, then we like eyes, mouth, nose, all the seeing, tasting, touching, hearing,

Starting point is 00:07:08 and whatnot, because it's handy to have those nearby the clusters of nerves so you don't have to send signals all the way from one end of your body to the other. Are there definitely areas where it gets super fuzzy? Is it worms? Because worms are giving me the most trouble

Starting point is 00:07:22 as I'm thinking. One thing you need to know when I say worms is that I don't mean any specific kind of animal i mean any animal that is long which uh well no you don't mean snakes do you worm is another problem there is worms are just invertebrates that are long and they are not related to each other but they are all called worms what the hell i didn't know that yeah uh and because, but they are all called worms. What the hell? I didn't know that. Yeah. And because of that, there are lots of worms that have very different situations on the top of the front end where the food goes in. That's the main thing that makes it the front end.

Starting point is 00:07:54 And it makes sense that like nervous tissues and sensory organs would cluster up there because that's where you got to find the food from. And the rest of the body is just for moving around and processing the food into worm so but like eventually i feel like it just there's not enough going on up there for it to be a head the biologists even worry about heads do they use that as a thing to even classify or is that just definitely in some organisms but not but not like across i don't think across a bunch of different species. I think it's more an interesting question of evolutionary history. So the idea, like the study of head formation is called cephalization. Maybe that's not the study of. When you want to know how heads came about, you study cephalization, which is like over many generations, these different facets of creatures migrated to one end of them and

Starting point is 00:08:47 formed a head so it was like the the appearance of heads in evolutionary time and like where it gets kind of fuzzy to answer your question hank is i think the invertebrate chordates so uh a notochord is like one thing it sets apart chordates it's like not quite a spine so you can't consider it a vertebrate but it's like a central nervous track sure like one step below vertebrates are the invertebrate chordates which are like um if you google tunicates they're kind of like tubes and sometimes they're like little guys that can move around, I think, too. But they're cute. They're tubes. Those are invertebrate chordates. And scientists are pretty sure those have heads.

Starting point is 00:09:31 But how those and other creatures like those invertebrate chordates then evolved into vertebrates, which have then a bony skull and a head that's clearly separated from a body, is a very big question in evolutionary biology and so somewhere in that is the gray area i think of like how did you we go from kind of blobby mouth on one end to worm and then to well you got bone in the worm so snake that's how evolution happened you went right from a swarm worm to snake to person this is the no one argue okay please tell me head has an interesting origin for the word it's a funny word it is kind of the english word head at least has been used throughout Germanic languages and has been relatively the same, I think, with a huh sound at the beginning.

Starting point is 00:10:31 So like old English, and I'm just going to say the letters. This is probably not how you pronounce it. It's hayfod, which is the top of the body or like the upper end of a slope. So it means like top or like an important person, like a ruler. And there's a lot of like h starting words but the proto-indo-european root so like when they mathematically go backwards uh it's kaput which i think is kind of funny and that is where it kind of gets more interesting because like all the words that are linguistically related to head feel like i guess that makes sense but looking at the list it's a very odd collection

Starting point is 00:11:14 so like for example cabbage cape capo like the guitar thing um cattle a head of cattle yeah what the heck kerchief mischief which is like like chief precipitation triceps just like a weird thing that all go back to head somehow do you want to head into the game show portion of the show okay yes please because this game is called whose head is it Okay, I'm in now. So imagine you're on a hike through the wilderness, or maybe you're swimming through the ocean. You're in a natural place. All around you are exciting bits of nature, like weird plants popping out of the ground, strange rocks. Then imagine you come across some bones.

Starting point is 00:11:59 And when you look closer, you realize that you have found a skull. The question is, whose head did that skull come from? Today, we're going to play Whose Head Is It Anyway, where you both will be playing skull detective. I'm going to describe a skull to you. And based on all those helpful clues, you're going to try and guess what animal it came from. Whoever guesses closest, based on my own definition of close, will win the point.

Starting point is 00:12:22 Are you ready? I've never been more excited in my life. I'm going to try and do this based on sort of taxonomy. So if you get close to the relationship between the species you choose and the actual one. We're going to start with round number one. The skull you have found is long. It's almost two feet long and its shape is elongated with a prominent beak at the end with 106 teeth lining its jaws. But the most striking part is what's going on the top of the head.

Starting point is 00:12:51 First, there are nostrils pointing upward. Second, the bones of the face and the forehead have slipped on top of each other, overlapping and collapsing like segments of a telescope. So whose head is it? Two feet long? Two feet long. I'm'm gonna guess a toucan a toucan has 106 teeth you know oh taxonomically close i'm gonna guess something it's either a bird or a reptile and i guess sam could get closer by guessing a reptile okay Okay. Now, what about the duck-billed dinosaur guy? Duck-billed dinosaur guy.

Starting point is 00:13:29 A myosaurus. Is that a duck-billed dinosaur guy? I don't know. I don't know either. I'm going to guess that, though. Oh, boy. Where does the duck-billed dinosaur live, Sam? Swampy water.

Starting point is 00:13:43 Okay. I'm going to go with sam because the animal i have described to you is a bottlenose dolphin okay i like that it just seems more dolphin-y to be a than a toucan anyway congratulations sam you guys really really rocked that one. I will say, dolphins and cetaceans have very odd skulls. Of course, their noses point upward because they have blowholes. And when cetaceans are developing in the womb, they actually initially have a more forward-facing nose like other animals. But as the baby continues to develop, the nose moves upwards and transforms into a blowhole. So it's like you can watch this happen embryonically. Weirdly,

Starting point is 00:14:25 despite the fact that they go through this transformation while developing, the way that the bones move in the skull to make this transformation differs between dolphins and whales. As for the telescoping forehead, there are references to this in people's observations of cetacean skulls going back at least 100 years, but researchers still don't know why it happens. Some think that it is the result of whales and dolphins swimming through the water, and the water pushes back on their heads and forces the bones to overlap. But researchers studying skull development have seen that skull bones actually begin forming that overlap in the womb.

Starting point is 00:14:56 So we just don't know. Wow. Anyway, round number two. Are you ready? This skull's width is just shy of two inches, so a lot smaller, but it's wide enough to accommodate a very large gaping mouth that allows this animal to ambush and eat vertebrates that are the same size that it is. While some of its relatives don't have teeth on their lower jaw,

Starting point is 00:15:17 this particular species has fang-like structures there that help it chomp down on its prey, and just above it are small pointy structures that look a bit like horns. Whose head is this? Has horns on its head? Yeah. Worm. Some kind of worm. Like one of those like sits.

Starting point is 00:15:42 What are those worms that have bones? Sicilians? Yes. Sicilians. That's what I'm guessing. All right. I'm going to guess a toad. Because it's a toad.

Starting point is 00:15:53 Damn it. I thought Sam had that because Sicilians are amphibians. So I was like, way to go, Sam. But no, it is the horned tree frog. It's not actually a toad, but it is, you know, what's a toad? tree frog. It's not actually a toad, but it is, you know, what's a toad? Most frogs have like really smooth skulls, but these frogs have much bumpier and they have more patterns. It's a trait called hyperossification. Scientists have found that this evolved more than 25 different times in frogs and that species with similar feeding habits and defenses ended up with

Starting point is 00:16:21 similar patterns and shapes on their skulls. In particular, hyperossification tends to be connected to frogs that like to eat big things or that would use their heads to protect themselves, a bit like our South American horn tree frog, which can eat animals that are as big as them. And even these small South American horn tree frogs can pack a huge bite. One study found that even a small frog whose head is just 45 millimeters wide has a bite with a force of 30 newtons. That's like balancing three liters of water on the end of your fingernail. Larger horned frogs whose heads can be more like 100 millimeters wide can bite with 51 liters of water on the end of your fingertips.

Starting point is 00:16:59 So watch out. What are they eating? Mice and stuff? Yeah. Like little mammals. Whatever they can get. Yeah. Yay. Okay. I found a picture of one mammals. Whatever they can get. Yeah. Yay.

Starting point is 00:17:05 Okay. I found a picture of one that's just swallowed a mouse. I love frogs. Another life. All right. It's time to see who's going to come out on top here or if it's going to end up in a tie because it's round three. This skull is around three inches long, but it has more than a dozen moving parts.

Starting point is 00:17:23 These different parts of the skull are connected through joints and ligaments. So even if the skull you're looking at belongs to a dead animal, you can move these different parts around, bringing to life the flexible motion that allowed the animal to suction food and move it through the mouth without a flexible tongue to guide it. So whose head is it? I think I know. Really? You think you know? Yeah. I think Sari gotta go first. Okay. This is like the direction of research I was

Starting point is 00:17:52 headed in for my fact, but I don't remember what animal. Because I was really interested in like flexible skulls. How snakes have flexible skulls and parrots do. And I couldn't find a fact that fit in. I think it's an eel. I think it's an eel.

Starting point is 00:18:07 I'm getting more worried that I don't know. Okay, what do you think it is? I think it's a human baby. A human baby. Yeah. I need to call the police because I found

Starting point is 00:18:19 a human baby skull. Sari's going away with this one because that, my friends, is a catfish. In particular, it's a channel catfish now fish have lots of bones in their heads I've just got to move on from this baby skull as fast as I can

Starting point is 00:18:33 well because they're flexible and because they have their things all organized so they can suck differently when they're babies babies do suck yeah babies suck so fish have a lot of bones in their heads and fewer fusions compared with other vertebrates, which allows them some flexibility in how they use their head when hunting prey. In fact, one of the highest number of skull bones that scientists have ever found comes from an extinct fish that had 156 bones in its head. six bones in its head. Scientists studying channel catfish have found that these bones are able to move in a coordinated way to create the suction that the fish use to capture their prey, though

Starting point is 00:19:11 they are much less coordinated when the catfish is actually swallowing the prey. That result points to the need for different levels of coordination in suction versus swallowing. Well, it's not clear what drives the difference between the coordination of those bones for those different tasks. So good. It's got to expand their whole head to suck those things into his mouth. So much trouble just to suck mud off the bottom of a pond. Gross. What a life.

Starting point is 00:19:34 What a life. But look, they probably have fewer days where they are just unhappy for no reason than I do. Oh, that's a really good point. Oh, well, that was a fun game and Sari came out on top. Next up, we're going to take a short break. Then it will be time for the fact off.

Starting point is 00:20:10 Welcome back, everybody. It's time for the fact off. Our panelists have brought science facts to present to me in an attempt to blow my mind. And after they have presented their facts, I will judge them and I will award Hank Bucks any way I see fit, mostly based on whether or not the topic in question would make a good TikTok. But to decide who goes first, I have a trivia question. To make better crash test dummies, we need to measure the size of the human head, the average human head, ideally of people of different ages and genders. And often people donate their bodies to research when they're done, and they can be like really

Starting point is 00:20:44 accessible ways to measure heads. But death and embalming practices can change the size of a person's head. So how much does the radius of an adult human head change after embalming? Get bigger or get smaller? We don't know. I think that it gets bigger. And what units are we supposed to give our answers? You know, let's do it in in

Starting point is 00:21:06 millimeters oh shit i don't know what that is okay small i'm gonna say five millimeters five millimeters for sari 10 i'm saying 10 uh well i'm gonna go ahead and say that sari riley won this round because it's 3.5. Yeah. 10 would be a lot, huh? So, Sarah, that means you get to decide who goes first. I'll go first. Okay.

Starting point is 00:21:32 I just want to preface my fact with a warning that I'm going to talk about an infectious viral disease, which maybe is not the escape that people want from tangents, but I think this is extremely cool and weird and gross,

Starting point is 00:21:43 but no worries if it's not for you right now. So if you want to skip my fact and just go to Sam's, you can. That being said, specifically, the viral disease I want to talk about is rabies. It's a virus that infects animals, particularly mammals, spread by biting or scratching each other, and humans infected with the rabies virus get nervous system damage and symptoms like nausea, violent movements, or a fear of water. And if you don't receive an expensive vaccine in time, it's usually fatal. Needless to say, it's a very bad disease. And in many parts of the world, it has been controlled or is being controlled

Starting point is 00:22:14 thanks to widespread animal treatment plans. Sometimes those plans involve hunting animals, and sometimes they involve the old public health staple, vaccination. So catch and release programs involving wild animals and injectable vaccines can be unruly and expensive. But there's one method we've been using across the world since the 1970s, hiding an oral form of the rabies vaccine in a delicious, nutritious, decapitated chicken head. nutritious decapitated chicken head. The earliest instance of researchers trying this out that I could find was in Switzerland in 1971 when they were trying to battle rabies outbreaks in red foxes and as such rabies that was plaguing any livestock or humans that came in contact with their spit. The scientists developed an oral vaccine of a live but weakened rabies virus

Starting point is 00:23:01 strain and tested a bunch of different tasty morsels as bait for the foxes, like sausages or dog biscuits. But the most tempting treat ended up being a straight up chicken head with a vaccine capsule shoved inside, kind of like a really gnarly pill pocket. I mean, I like this because it's like there's no shortage of chicken heads.

Starting point is 00:23:18 Yeah, what else are you going to do with them? And also I like it because if a fox wants to eat a chicken head, it's not going to eat part of a chicken head. You know, there's not like an option to like pick at it. You just like, there's only one way to eat this is to put it in my mouth and crunch the whole thing. Yeah. And so even whether they swallowed the heads or just gnawed on them and got like the vaccine goop along with the chicken goop, it worked in october 1978 after fine-tuning their methods these researchers started scattering

Starting point is 00:23:47 thousands of chicken heads across switzerland by flinging them onto walking paths roads and from helicopters and despite lots of public worries that these live but weekend virus stuffed chicken heads would actually spread more rabies oh yeah it continued to work and we knew it worked because there was a chemical marker included in the oral vaccine that researchers could detect and captured Oh, yeah. Of course. and hundreds of thousands more to come. And as more countries have adopted oral rabies vaccines for wild animals, they're trying out different bait like mass-produced meat or fish tablets, but the chicken head method is still going strong. Why would they try something else?

Starting point is 00:24:36 It's working, and everyone has too many chicken heads. There's no country on Earth that has not enough chicken. They're like, oh, we ran out. No, you never run out of chicken heads. We eat so much chicken. I think they want to mass produce something else.

Starting point is 00:24:51 They don't want to stuff pills into chicken heads. I think that's probably what they want. But yeah, so even despite sentiments like that, it's still going. A 1998 study on oral vaccines for rabid dogs in Tunisia, for example, found chicken head baits to be appealing to populations of dogs across different geographic and socioeconomic regions. And a 2020 study that tested out different baits for rabid jackals in South Africa tested out fish meal, pieces of red meat, and chicken heads. And the chicken heads won. They're a classic.

Starting point is 00:25:21 Yum, yum. Everybody loves them. They love the tasty treat um so apparently there is something just so enticing about this grody poultry industry waste product uh it makes it super good for fighting rabies around the world or at least tricking hungry wild animals into getting an oral vaccine now let's we could only do it to Yeah, what's the people equivalent of chicken head? I mean, a chicken nugget. I know exactly what it is.

Starting point is 00:25:51 All right, Sam, what do you got? One of the greatest things about having a head is wearing hats. Cool hats, funny hats, hats that keep you warm. Hats are one of the greatest inventions humans have ever thought of. Unfortunately, seemingly no other species on earth has unlocked hat technology, but recent research has found that another animal may be making their first steps into the world of hats. And the question is whether they're doing it in pursuit of function or fashion. So in 2007, a biologist was observing crocodiles in India when he noted that some of them had sticks balanced on

Starting point is 00:26:25 their heads and snouts, and every now and then a bird would swoop over and try to take a stick away from the crocodile, and the crocodile would snap at the bird and try to catch it. This scientist never saw the crocodile successfully catch a bird with this method, but it got the old science wheels turning in his brain, so he started observing American alligators and witnessed the same stick on head behavior, and in 2013, a study of his findings about this behavior was published. Specifically, the paper noted that alligators that lived near large groups of birds would float around with sticks on their heads during the time periods when the birds were building their nests. So the alligators seemed to have, according to the paper, worked out that birds are desperate for sticks during these times.

Starting point is 00:27:03 And I guess the birds either just aren't paying attention or they're more likely to make bad decisions. And then alligator lunchtime. Meanwhile, the report also suggested that alligators that don't live near birds weren't seen with sticks on their heads. So it sort of stood to reason that the stick on head thing was a conscious decision based on the bird's presence on the part of the alligators.

Starting point is 00:27:22 Now to our human brains, that might seem like an easy trick, but it might just constitute the first ever recorded instance of tool use in reptiles. And the use of bait, like the stick, is even rarer than tool use. So that means that alligators might just be smarter than we think, which is already pretty smart because they raise their young and stuff like that.

Starting point is 00:27:41 But it might also mean that non-avian dinosaur ancestors of alligators and crocodiles might have used tools and also have been smarter than we think. However, as often happens when eggheads are involved, another group of scientists came along in 2019 to shed some doubt on the whole hat situation. So for one thing, and you might have noticed while I was talking, apparently, according to these second researchers, the original paper doesn't document any alligators actually catching any birds.

Starting point is 00:28:09 And I couldn't read the paper because it was paywalled. But yeah, a couple of the articles I read describe the alligator catching a bird. But apparently that's not in the paper. That's just like conjecture on the part of the person writing the article. But I couldn't confirm that. So this new team observed alligators, but this new team said that that was the case. And so they observed alligators at two alligator farms, one near a bunch of birds and one not. So they threw a bunch of sticks to the alligators. And what they found was that alligators at both locations seemed to just like putting sticks on their heads. They described it as the alligators displaying the sticks. And it didn't really

Starting point is 00:28:46 say what that means, but I guess they were like, I got a stick on my head. But they didn't see any evidence that the alligators were specifically targeting birds

Starting point is 00:28:52 with this ploy because they were both doing it. So they might have just been doing it for fun. So wearing hats for fun or some other reason

Starting point is 00:29:00 is also tool use, I think, probably. But the question as to why they do it seems to be entirely up in the air, like the birds are trying to eat. And I don't really know what the takeaway of all this is. Like they were testing alligators in a gator farm, and that seems significant to me for some reason.

Starting point is 00:29:16 Like they might know different stuff. But either way, alligators might be inventing alligator hats right before our eyes. And that's all I really need to know. I mean, they're doing it awfully slowly, considering alligators have basically been around the whole time i feel like if alligators are wearing hats now they were wearing hats 60 million years ago like there's not but i don't know i wasn't there but i'm looking at pictures of alligators wearing they look so stupid and i have to say like it clearly is on purpose like there's no one can say oops like he just ran into some sticks no i have six i put a bunch of sticks on my head on

Starting point is 00:29:51 purpose yeah why don't ask questions i'm an alligator i will hurt you i'll eat you fashion all right so i have to choose between alligators invented hats we don't know whether they just like it or they're using it for murder. Or wild animals are frequently vaccinated against rabies with medicated chicken heads. Which of these head facts will I choose? This is hard. Oh, boy. I have to go with the hats.

Starting point is 00:30:27 Yeah. They are really cute. Chicken heads don't look cute. Chicken heads are... There's nothing much less cute than a chicken head. I gotta go with cute hats, but that creates a problem because that means that it's...

Starting point is 00:30:41 Sari was headed into the lead. So now, is it good enough to overt's Sari was headed into the lead. So now is it good enough to overtake Sari? Sam are you gonna buy one of my Pelican NFTs? I can't afford

Starting point is 00:30:52 not to honestly. All right. Sam's the winner of the episode. Hank already knew my answer was no. Looked into my eyes and was like

Starting point is 00:31:03 this bitch isn't gonna buy a single NFC in her entire life. All right. It is time to ask the science couch. We've got listener questions for our couch of finely honed scientific minds. It's from Larrykin.fm on Twitter who asks, how is there a blood brain barrier if there's blood in my brain? That's a great point. It is an incorrectly named thing. The blood brain barrier. I think. Is it? Sari, is it? It's not like a saran wrap around your brain, unfortunately.

Starting point is 00:31:40 Well, yeah, because I feel like I do have oxygen, some oxygen in my brain. Well, yeah, because I feel like I do have oxygen, some oxygen in my brain. Yes, you need it there. So I'd be very concerning if you had like a hermetically sealed brain. So where's the barrier that keeps all of the pathogens out of my brain tissue? So to understand the barrier, you have to understand how blood vessels work. So your entire body isn't just bathed in blood. The whole point of your cardiovascular system is to pump the blood around your body and then through the walls of the blood vessels, particularly the small,

Starting point is 00:32:13 thin ones like capillaries. Those do nutrient exchange and oxygen exchange and carbon dioxide exchange with the other cells in your body. So like more vascularized tissue have more little blood vessels running through it. And then through diffusion through the walls of the blood vessels is how things get back and forth. And the blood brain barrier, your brain needs nutrients and it needs oxygen and it needs some of this stuff,

Starting point is 00:32:41 but you just want to protect it from more of the bad stuff from the rest of your body because your brain is so important. And like your nervous system in general is like if something goes wrong there, a lot of things can go wrong. capillaries that make it really hard for molecules that aren't of a certain type to get through. So for entrance into the brain, you need molecules for the most part to be lipid soluble, less than 400 Daltons, which is like a measure of size, and like substrates of a certain type of transporter. So there are like transporters within the blood vessels. And basically, there's all this mechanism with certain types of cell junctions that glue cells together, basically. Certain types of cells, like astrocytes, are wrapped around. So not quite sarin wrap, but there's like layers of cells that aren't present in other tissues and certain transporters that basically act as many layers of security

Starting point is 00:33:52 guards to make sure that only the nutrients that you want to get to your nervous system, to your brain, get there. But that being said, some things like fit those criteria, like ethanol, for example, is lipid soluble enough to get past the blood-brain barrier and into your brain which is why like drunkenness happens um and certain small molecule drugs may cross the blood-brain barrier uh because of this like lipid mediation diffusion and it's a challenge it's like both a characteristic of things that can like affect our central nervous system whether it's like drinking alcohol and it's a criteria if we're trying to develop drugs to like target a central nervous system so a lot of what we

Starting point is 00:34:40 develop don't often meet these criteria to pass the blood-brain barrier. So if you're trying to treat a neurological condition, you have to somehow cater the drug that you're building to those characteristics to be able to cross it, which is a very interesting puzzle of not only how do we develop this drug to target this disease, but how do we get it past this like logic puzzle sequence, this spy, many layers of protection to get to the brain. So it's not preventing the blood from getting to, or at least not preventing

Starting point is 00:35:13 the oxygen from getting to the brain. But it is, it's just an extra layer of protection that also creates problems for pharmaceutical designers. Yeah.

Starting point is 00:35:23 You can just cut my answer and just put that in and save some time. If you want to ask the Science Couch your questions, you can follow us on Twitter at SciShow Tangents, where we will tweet out topics for upcoming episodes every week. Or you can join the SciShow Tangents Patreon and ask us on Discord. Thanks to James on Discord at LizardIsANerd. And everybody else who asked us your questions for this episode. If you like this show and you want to help us out, it's real easy to do that. You can go to patreon.com slash SciShowTangents and become a patron. You can get access to our newsletter and our bonus episodes and our Cars 2 commentary,

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Starting point is 00:36:18 for SciShow Tangents, just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz. SciShow Tangents is created by all of us and produced by Sam Schultz, who

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Starting point is 00:36:44 Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lighted. But one more thing. It's easy to think about the head and the butt as opposite ends of animals. After all, you don't want to be excreting where you're eating and whatnot. But for the blind, fleshy, pink cave fish in the genus Ambilopsidae, that isn't true. Their anus is on their head. Opsity. Uh-huh.

Starting point is 00:37:22 That isn't true. Their anus is on their head, probably because their reproductive hole, called a vent, migrated across evolutionary time and brought the anus along with it. Uh-oh. These little weirdos probably have head vents because they incubate their babies in their gills, and it's safer if the eggs travel a shorter distance from hole to nursery. So I guess they found a parenting strategy that works for their extreme environment, but as a consequence, they're quite literally buttheads. My phone was wrong.

Starting point is 00:37:48 It's not the opposite. I'm so sorry. Yeah. Look, why doesn't everything happen up here? Just need a head and then a body and then all the everything, all the holes on the head. You can't have separate holes down the bottom. That's super complicated. Yeah.

Starting point is 00:38:03 You just need a head with little legs at the bottom of it. And then your butt can be at the back and the bottom of your head. And I've just designed the perfect organism. Maybe I have big arms too. Oh, grab stuff off of shelves. Can I buy an NFT of that? Yeah, I'm making them right now. I mean, it does seem inevitable.

Starting point is 00:38:21 If you have had an ugly thought, if you have a picture of an ugly thing in your mind, it's just waiting to be a toothy NFT. Oh no, you're going to get in trouble.

SciShow Tangents - Heads

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