How does my brain store information?
Why can I hold off a bathroom stop when I'm driving? How does my brain store information? Why don't birds sitting on power lines get electrocuted? Why do bubbles in a bath disappear when the water gets cold? Why are rainbows such perfect arches? What causes an itchy backside in the middle of the night? Why have spiders never evolved wings? How do our bodies maintain a constant temperature? Plus, what exactly is going on with the volcano in Guatemala...
Eusebius - Chris, good morning to you.
Chris - Hey, good morning.
Eusebius - Guatemala has been in the news for some very hot and scary reasons. And I always forget some of the important geology around these kind of events when you see eruptions and stuff. Can we start there as our science story for the week?
Chris - Yes. What a what a wonderful suggestion. But not for the people in Guatemala of course where, of course the Fuego volcano erupted dramatically last Sunday, and one of the first things it did was to create a glowing cloud a Nuée Ardente. And people are often gobsmacked when they learn that these these clouds of gas and dust come rolling down a hill at some 700 kilometres an hour or more and they can be at 700 degrees C. So anything in their path really is just obliterated, because not only is there a huge rush of material. And these volcanoes are emitting, when they're going off at peak, hundreds of thousands of tons of material every second. And so you've got this maelstrom of material coming incredibly fast and it's robbing all of the oxygen from the area, so life is going to find it very hard to compete with that. But then after that came lava flows and the amount of dust and material that's being ejected is also causing very large amounts of mass to fall down onto surrounding buildings and areas which is which is crushing things. So it's a very devastating thing. And of course once you've got that fine dust there if it rains, because very often this dust in the atmosphere then can trigger rainfall, you then get mudflows as well, because the very fine particles of dust liquefy with all the water and turn into this gushing torrents of mud, which means you're then hitting all of the environment with hundreds of thousands of tons of material moving very very quickly in the form of mud. So having been sizzled and asphyxiated you then get washed away and thrown in a mud bath. So it's a terribly dramatic situation and very very bad for people who are there who are trying to rescue loved ones and so on.
Eusebius - Absolutely. Glenn in Soweto, good morning to you. What is your question for Chris?
Glenn - Morning. My question is that why is it if you want to go to the loo and then you are driving you can hold it for maybe an hour or two. But after that you get out at the door you feel like running. You can't even hold it youself but before I did manage to hold it?
Chris - I think this is a case Glenn of mind over bladder actually. Because when you know you're in the car and you know you need the loo but you know you can't go to the loo, for obvious reasons, then what you do is you know I have to hold this. And so there's very strong top-down influence from your cognitive and from your consciousness saying I must suppress my bladder. But when you know you're getting close to the loo, your brain starts to prepare for the fact that I'm going to have a wee in a minute that I'm desperate for and I'm going to relax all the muscles that are holding the wee in and let it out. And so as you get closer to the to the toilet your cognitive resolve weakens, your muscles start to relax, and your ability to hang on for longer also weakens and diminishes, and so actually that's part of the preparation process. Once you get to the loo of course you can then start going. Sometimes you can't because you've got so good at holding on it takes a bit longer to get started. But that's the reason: it's mind over bladder. It's the psychology of knowing that you can't do something, you can't go to the loo and having to do something about it versus I'm almost at the loo and I'm going to prepare myself for the best wee I've ever had in my life.
Eusebius - Neville in Boksburg. Good morning to you and welcome to the show today. What question have you got for us?
Neville - Good morning. I'd like to ask Chris a question. How does the brain work? How does it store information? I can understand a computer or electronic storing, but I cannot comprehend the brain. That's my question.
Eusebius - Okay. Thanks for that one.
Chris - Yes you, and actually pretty much every neuroscientist that's walked the earth in the last hundred years or so. You're in good company, Neville. We've slowly begun to understand more about what the brain is made of. We know that there are collections of cells, not just nerve cells, there's a 100 billion or so nerve cells. There are other supporting cells called glial cells, there are blood vessels, so the brain is an electrical organ. These nerve cells talk to each other using electrical and chemical signals. We know they're arranged into groups where grouped nerve cells all do similar jobs to each other. And we know that one of the things they do is connect from one nerve cell, using a thin straw like projection called an axon, to other nerve cells. Some of which can be in very remote parts of the brain, others can be nearby. They can connect in ways that either activate the cells they're connected to or turn off the cells that they're connected to. They do this via a connection between the two cells called a sinapse and, at that sinapse you squirt some chemical from one cell onto the other cell to change the target cells activity. We know that those sinapses can be remodelled or changed in the brain on an ongoing or continuous basis, and they can effectively be strengthened or weakened. And so we have an idea in our minds that the way the brain processes and stores information is that when we learn something we alter the pattern of connections. We may remove some connections, we may add new connections. And in this way, in the same way that a computer generates logic when you put a stimulus or piece of information into a computer circuit, you have a system of logic that then produces a result. We think that the brain stores information in a similar way at these junctions or unions between nerve cells or populations of nerve cells at these sinapses. And there's quite good evidence that, in fact, that's how memories are stored. You store memories in the form of stronger or weaker connections between nerve cells and it is possible by rewriting those connections to rewrite memories or even erase memories. There is some evidence showing that if you put a chemical into the brain that detaches these nerve cells apart from each other you can obliterate memories right across individual's life. Not in humans, they've done this in animals, but it's similar physiology going on in a human brain. So the answer is we don't know the answer to your question, but we do have theories that nerves work in networks or circuits, and the information is stored as connections between populations of nerve cells.
Eusebius - Thanks so much for that question. Victor, good morning to you. Welcome.
Victor - Good morning Eusebius. Good morning Chris. My question is about birds and electrocution on the wires that they sit on. And yet they have blood, they have heart, they have flesh and they've got bones, and they drink water. My question is why aren't they getting electrocuted?
Chris - Got it. Okay. Well, when when a bird sits on a power line it is not connected to energy at two different potentials. The reason electricity flows from a power line through your house, through your gadgets, and then makes something useful happen for you is because the gadget you're connected to the power line is offering the electricity a path from a high potential, in the power line to a low potential, earth. So the electricity wants to flow from the power line to that low potential. If a bird is just sitting on the powerline, the bird is not offering the electricity a path to anywhere because the electricity and the cable, if it were to go through the bird, would end up where? Back in the same cable it came from and therefore there's no potential difference between the electricity in the cable and the bird's body. If the bird were to cross between the cable and earth, or between one of the phases of the cables and another phase offering a different potential, a different voltage essentially between the one cable and the second, and that electricity could only cross that potential through the bird's body, then a large current would flow through the bird and that would lead to the death of the bird. But when the birds just sit on the cable they are not offering the electricity any other route to anywhere, there's no potential difference between the bird, and the cable and electricity only flows when there is a potential difference. So no electricity flows, no current, therefore no electrocution.
Eusebius - Lovely. Thanks for your question Victor. We really do appreciate it. Sixteen minutes after 10:00 if you've just joined us. It is of course a Friday which means we're talking to Chris. And if you want to call us with your questions in the world of science please do so right now. We have him for another 10 minutes or so. Capetonians,you can call us on 0 2 1 4 4 6 0 5 6 7. And of course here in Johannesburg your science question on the number 0 1 1 8 8 3 0 7 0 2.
Eusebius - Marikar, good morning and welcome.
Markiar - Good morning Eusebius. How are your?
Eusebius - I'm well, thank you.
Marikar - I've got a question for the Naked Scientists. I want to after you bubbles with a bubble bath.
Eusebius - Yes, a good idea in winter.
Marikar - Why does it take time for the foam to disolve when you put in the hot water, but when you put in cold water the foam disolves very quickly?
Eusebius - Okay. Chris, I'm not sure if you heard that audibly enough. Did you hear the question?
Chris - Not a very good line if I'm honest.
Eusebius - I think you were saying something along the lines of when you take a lovely hot bubble bath, which I feel like doing right now, that the cold water results in the bubbles dissolving more quickly than the hot water. What explains that?
Chris - Well, what are bubbles first of all? What's happened when you've put bubble bath in your bath is that you have added a detergent. Detergents reduce the surface tension - the stickiness of water. And if you make water molecules a bit less sticky then what they can do is to form a bubble because gas can get trapped inside the water and they can spread out to form a bubble film. Normally what happens is the water molecules are so sticky, they want to get so close together, that the bubble can't form properly. So by weakening the attraction between the water molecules by the detergent getting in the way, you can actually spread them out to make a bubble that you can see. Now when you first run a bath you've got nice hot water there, you put the bubble bath in, you get bubbles because the water that's falling into the bath from the tap pushes some air in with it, and that air is then trapped inside the bubbles and so the bubbles form as you add water to the bath. So it's not surprising that when the bath is
first poured or filled and is full of hot water you see lots of bubbles. You come back later and the water's now cold and the bubbles have gone. And you think well, is the cold water less amenable to having bubbles in it or has something else happened? And, actually, what's happened is the bubbles, after you make them they're weak, and they're only going to last for a certain period of time because water is evaporating from the surface of the bubble film weakening the bubble, so the bubbles are going to naturally pop. And you start with millions and millions of bubbles and, after a little while, you've popped lots of the bubbles so they disappear. So, not surprisingly, when you come back to your bath and it's got cold later, the bubbles aren't there because they've all naturally popped which they do spontaneously. Also, if they're a little bit colder because the water's colder, the gas will shrink a little bit that's in the bubbles, so that may also make them look smaller and less impressive than when you had big chunky bubbles to start with.
Eusebius - Annie, thanks for calling in. What is your question?
Annie - Oh me.
Eusebius - Oh yes.
Annie - Okay. My question is about a rainbow. I understand the whole refraction and relection and all of that stuff. But I don't understand how come a rainbow is always in such a perfect arch and how the colours are always exactly the same and in the exact same order, and they don't mix around, or bend together, or whatever, like it always looks the same?
Eusebius - Okay, s that's a good question. I know that you've answered this question many times before. I think the first part of the question wasn't only about the colors, Chris. Well maybe I'm just adding on extra one here. Why is it always curved? Why does it have the shape that it has?
Chris - Okay. Hello Annie. And just for those who are not necessarily in the know, the reason we get rainbows is because you end up with light entering raindrops. So you need a rainy sky with a bright sun behind you to illuminate the rainy sky. The rays of sunlight are coming in parallel and they're white. But white light is made up of lots of different colors which when seen together look white but, in fact, it's a mixture. And when you look at light shone through a prism where the light spin split up into all those different colors, those are the colors that are making the rainbow. The parallel white light rays hit raindrops in that wet sky. They refract, which means bend, because the light changes speed when it goes from the air into the liquid medium. Different colors bend by different amounts but they always bend by the same amount. So the red ones bend at a different amount of bend than the shorter wavelength blue colours. And because that number is always the same because it's the same white light going into the same medium, water from air into water, the amount of bend is going to be identical, so this has the effect of spreading out the colours. They hit the back inside surface of the raindrop, which is like a miniature mirror, and it reflects the light back out at you. And because all of the different wavelengths have bent by different amounts they're spread out by a certain amount and, therefore, they start to come towards you as a cone. So if you imagine a point of light spreading out it's going to come to you in a cone shape, but you only see a perfect arc - half the rainbow - because the other half of that cone is going to hit the ground because it's shining at the ground. You see the bit of the Rainbow which is the cone spreading out towards your line of sight. And each of those colors has been bent by a certain amount inside the raindrop and by a proportional amount, which is why you see bands of color of the rainbow, and that's why it has the shape that it does. And the reason it's a curve is because the ground is in the way for half of it. If you were to see a rainbow from up in the air it would look like a circle shape.
Eusebius - Okay. Interesting. Thanks so much for calling in. Lona, you've called in after a couple of weeks and finally you've managed to get through. Thank you for your patience for the last three weeks. What is the question that you have been burning to ask Chris?
Lona - Good morning gentlemen. It's about anal pruritus. Where does it come from? Why does it sometimes simply disappear for months? And why does it usually rear its ugly head in the middle of the night while you asleep?
Chris - Ha, ha, yes. That can be a pain in the backside can't it? I don't know about anal pruritus, but so the question is about itchy bum and what can cause an itchy bum. And this is very common, lots of people have it. There's a reason why your bum can get itchy. One of the reasons, the nasty reason, is that you can have parasites - you can have worms. There are certain species of worms that live in the intestine and they have evolved to know when it is night time because you're less likely to respond to them. They come down towards the anus when you're sleeping. They actually plant eggs outside the margin of the anus and they make your bum itch. And the mechanism for the worm is that it wants to make you scratch your bum and then you get the worm eggs on the ends of your fingers and under your fingernails, and then those people who bite their nails or put their fingers in their mouths a lot, you transfer the eggs back into your mouth and then you re-infect yourself with more of these intestinal worms and the numbers can therefore climb to quite a high worm burden. That's one way. Another reason people can have an itchy bum is because, if you think about, it this area has got lots of microorganisms which live in your intestinal passage, yeasts, other bacteria. It's also a damp place because you've actually got the cheeks keeping everything moist there and you've got some natural secretions from that area. And also, as a result of going to the toilet, you might be traumatizing the skin around the area a bit when you use paper towel to wipe after going to the lavatory. And that trauma can break down the skin a little bit and allow some of those microorganisms, for instance yeasts, to infect the skin and as a result you get an itchy infection there. And as that is fought off by the immune system the itchiness goes away and that's why you can get this relapsing and remitting course where it comes and it goes. Other things that also affect the anatomy like hemorrhoids which also can make secretions. They can make it more likely your scratch and irritate the area. They will also be a risk factor for this. So there's a whole range of reasons why you may have an itchy bum. They range from more important to less important, easier to treat to more difficult to treat, but if it is persistent you should go and see a doctor because you probably can get some relief quite quickly.
Eusebius - Jerome, welcome to the show.
Jerome - Hello there, yeah. My question concerns kind of evolution. Why is it that no spider ever has evolved wings and is able to fly around and predates with wings?
Chris - Hi Jerome.
Eusebius - I think that's a very interesting question, Chris.
Chris - Well the point is that all animals on Earth have a niche. In other words, they've got a part of the environment that they occupy and occupy it very well. And the pressure of natural selection means that they are continuously being forced to innovate and evolve to stay in pace, and stay in competition to maintain their hold on that niche as other things come in and try to exploit it. So you could say well, why haven't humans grown wings so that we can fly around? Because you know arguably we could get around a lot faster if we could fly than if we're on two legs. But then you look at a bird and you think well it is pretty good when it's flying around but, at the same time, it's in real trouble when it's on the ground. So birds have adapted to an aerial life in trees. We've adapted to a life on the ground. Spiders are extremely successful as a species. The fact there are so many of them that they've been around for millions and millions of years and they have evolved very clever tactics, including things like webs and other ways of catching prey. Quite frankly, they don't need to fly because their dinner comes to them. So they've evolved to make a very complex track network in the form of their spider web and then things that do have wings blunder into them, and because they have wings they're a bit discordinated and can't escape, so the spider eats them. So you could argue the spider hasn't evolved wings because it doesn't need to because it's far too successful already.
Eusebius - We'll give the final question to Mydorta in Kempton Park what do you and I ask my Mydorta.
Mydorta - Hi, good morning Eusebius. My question to the scientists is that I would like to know what keeps our body temperature normal at 37 degrees, even on cold extreme weather or even on hot extreme weather?
Eusebius - Lovely question. Chris.
Chris - Yeah. What a wonderful question and a good one to end on. The answer is that in a homeothermic organism, which means homeo means the same thermic temperature like human. All mammals in fact, we're warm blooded, that's the other way of looking at this. The body goes to extreme lengths to keep our temperature as close to a set point, in us about 37 degrees, as it can. And the reason it does that is because your body works best at that temperature and that means you can be far more active. You can have a far bigger brain and be far more successful if you behave like that than if you're relying on say heat from the Sun, because on a cold day you're going to be a lot less active and you're more likely to turn into someone's lunch. So how does the body do this? Well, part of it's down your brain. At the bottom of your brain as a structure called the hypothalamus, and the hypothalamus contains lots of groups of nerve cells who do very specific jobs to keep you alive. And there are regions of the hypothalamus which have an important role in retaining heat in the body if you get too cold, and they have important jobs in other parts of the hypothalamus in losing heat if you get too hot. The hypothalamus is continuously testing body temperature by sampling the blood temperature. And it's also receiving connections from the skin so it knows what temperature your skin is at. And it integrates all this information and it then puts in place various mechanisms either to help you to lose a bit of heat if you're becoming too warm, or to gain more heat if you're getting too cold. Now if you're getting too hot you can imagine, we all know what happens on a hot day we sweat. So what the hypothalamus does is it tells the nervous system: open up blood vessels in the skin, divert lots more blood than normal into the skin close to the surface of the skin. This will enable hot blood to radiate heat out of the body into the environment. It also supplies sweat glands much more with more blood so you can make sweat, and the sweat goes on the skin surface and evaporates taking with it more of that heat from the hot blood underneath. And it also influences your behaviour by telling you gosh, I feel hot take off a coat; take a jumper off; seek shade. It changes your behaviour and reduces the input of heat into the body and also things like going getting a cold drink. Now when you're too cold the reverse happens. It knows you are losing temperature. It persuades your blood vessels right, close down, divert heat away from the surface of the body, divert heat away from the peripheries like fingers and toes. Concentrate the blood flow in the inner core of the body to keep you warm. Increase your metabolism. Push up your metabolic rate so you burn more calories which turn into heat as a waste product, that will keep you warm. Also do things like put on a coat. So it enacts all these behavioral changes which help us to maintain a rigid, rigidly controlled constant temperature except when we become unwell. And then it allows the temperature to climb a bit because it reasons that actually by turning up the temperature it's nastier for the invading infection than is for you. So you can tolerate it a bit for the while but the bacterium can't and so you sort of burn off the infection with a fever. So that's the rationale behind it.
Eusebius - Thank you Chris. So much appreciated. Thanks for your insights and all the learning moments. We'll do it again next week.
Chris - I'm already looking forward to it. Thanks everyone. Take care. Bye bye.
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