Can any organ get cancer? Why do mints make water feel cooler? Why do cockroaches face upwards when they die? What causes eye twitch? What's the best exercise after a hip replacement? How would high water pressue affect the body? Why is extreme cold as painful as extreme heat? Plus, developments are made with the first human head transplants...
Eusebius - Good morning Chris!
Chris - Good morning.
Eusebius - I thought this was sci fi until I looked at the top of my header. Pardon the pun on the first part of the word head. The world's first human head transplant.
Chris - Well it hasn't been done quite yet on a live person but this is a report that came out last month, and this is actually practicing the procedure on a caderveric donor. So this is the work that scientists in a number of countries have been looking at: whether it's possible to move a head from one individual to a new body. Now there are a number of practical aspects to this. One of them is that if your body claps out but your brain is good then, obviously, you'd be losing your entire being for the sake of a clapped out body. So if you could get a new one then, potentially, you'd give a new lease of life to the head. Now there are some problems though which is that whilst it's possible to reconnect the blood vessels, and that's critical because the brain has one of the highest metabolic rates in the body. It needs about 20 per cent of the oxygen that you use in any one moment to go straight into the brain to supply it. The thing that you can't do is reconnect the nerves to the rest of the body so, although you could get the head off and you could connect it onto a new body and you could replumb in the blood supply and that would keep the brain alive so the person would therefore be conscious potentially. What you can't do is to make the spinal cord, which is the connection between the brain and the rest of your body reconnect. Because when you damage the central nervous system, which you'd have to do, you'd have to sever the spinal cord to get the head off the body it would be very difficult indeed to actually give that person any quality of life because the nerve connections between the brain going out down the spinal cord so you could move they would be lost. The sensations flowing into the spinal cord from the skin and then up to the brain, they would be lost so that the person would effectively have sort of locked in syndrome. They might be able to move their face, they mihgt be able to move their eyes, they might be able to see, but other than that they wouldn't be able do anything. So doctors are interested in doing this as perhaps a stop-gap, but until we solve the problem of how to make the central nervous system repair itself then this really does remain very much rooted in the realms of science fiction.
优西比乌,这是除了乙ical questions and the philosophical ones about the person it's on. It sounds very fascinating - a story that will turn heads...! Philip, good morning.
Philip - Good morning Eusebius. I just want to ask the Naked Scientist when birds fly, you never see birds dropping out of the sky. So does it mean that birds they don't die while they're flying or do they have to sit down to physically die because you never see them dying in the air, you never see them dying in flight?
Chris - Hello Philip. It's very important observation and I salute you for thinking about this scientifically. The answer is that flight is a very metabolically demanding process and so a bird has to feel in pretty good condition before it's wanting to fly anyway because birds are aware of the danger. I mean if they're flying and they're taken ill that would be bad for their health. So a bird that's not feeling very well tends to retreat to its roost and sit there and feel sorry for itself. It's not going to want to fly unless it absolutely has to so that's probably the reason. But it does happen because, of course, there are some birds on Earth, the Tern for example, makes a lifetime series of migrations that tot up to journeys to the moon and back in terms of the distance it flies. So some birds spend almost all the time flying so, inevitably, if something happens to one of those they will just drop out of the sky and die. But the amount of time as a proportion that they spent flying compared to roosting if not feeling well means that, on average, they're going to die on their perch rather than dying dropping out of the sky. But it does happen.
Eusebius - Zania wants to know on the SMS line. Why does the human heart not get cancer and are there any other organs that are not susceptible to malignancy?
Chris - Well actually, the human heart can get cancer and you can get a condition called an atrial myxoma. It's rare, it doesn't happen very often but it does happen and it happens often enough that doctors know about it. So pretty much every organ in your body is made of cells and those cells contain DNA. Cancer is a genetic disorder so if you damage DNA then you can cause cells to begin to disobey the normal constraints on how they grow and how they arrest their growth. And if they start to disobey those constraints and they don't control their growth they can turn into a cancer which is what effectively happens in any organ so, therefore, any part of your body can become cancerous. The organs that tend to be, or the tissues tend to be most susceptible to cancer are those that have cells growing very fast, or being injured a lot and having to repair themselves very fast or are susceptible to, or exposed to things that cause cancer, carcinogens. Things like skin being exposed to ultraviolet that can damage your DNA or something in your diet that damages your liver and keeps on damaging your liver, like alcohol, that makes you become cirrhotic and the cirrhosis then is a risk factor for getting cancer. So the heart can definitely get cancer but the heart 's made of non-dividing tissue muscle cells therefore it's lower susceptibility to cancer, but it can definitely happen.
Eusebius - Vic, you have a question that is almost literally a cool question.
Vic - Thank you Eusebius. My question is if you have mint sweet in your mouth and you drink water, let's say tap water, it seems as cool as the one that comes from the fridge. What is the reason for that?
Eusebius - You've got some cool questions today Chris!
Chris - And you got some cool jokes or some good one liners anyway! It's a succession of them. I'm wondering what's goint to come next...!
Eusebius - Thank you!
Chris - This is another excellent observation. Thank you Vic for this. The reason for this; mint contains various chemicals, including menthols, and these binds to a specific target on nerve cells in your mouth. This target is called TRP-M8. And this sits on the surface of a nerve cell and when it sees chemicals in mint it opens pores on the surface of the nerve cell, and these pores allow charged particles to go into and change the activity of the nerve cell. The nerve cells that they target specifically are those cells that detect temperature. And when you activate this TRP-M8 ion channel, or pour, it triggers that nerve cell to tell the brain I am experiencing a cold sensation. So when you put a mint in your mouth, even though the temperature hasn't changed, it triggers the nervous system to think the temperature has changed and therefore if you put cold water into your mouth, even though the water isn't very cold, the nerves are now responding as though the water were much colder than it really is. So you get the distinct impression that you're drinking something very cold even though you're not. And the reverse effect of this is hot chilli pepper. When you take capsaicin into your mouth, which is what the ingredient is in chillies that causes the burning sensation, this activates another channel called TRP V1, which is on the cells or the nerve fibres that sense pain and temperature, heat specifically. That fools your mouth into thinking it's hotter than it really is which is why if you then drink a warm drink actually it feels excruciatingly hot because your nerves are now more sensitized to high temperatures. So these two effects are sort of diametrically opposed. TRP-M8 in menthol and mint makes you feel colder than you really are so cold things feel colder than they really are. TRP-V1 in chilli makes hot things feel hotter than they really are. In both cases though, if you put a thermometer in the mouth, and we've done this experiment on the Naked Scientists, the temperature has not changed. Its just your perception of the temperature and your sensitivity to temperature that has.
Eusebius - Jerbula wants to know on the SMS line if there's a scientific reason, Chris, why a cockroach faces upwards when it dies?
Chris - I think probably, and I don't know the answer to this but I suspect that what he means is why do you find cockroaches lying on their back with their legs in the air? I think this comes down to just a stability thing. When a cockroach is about to "peg out" then it doesn't just sort of suddenly stop moving and die in-situ. It struggles for a while and tries to keep going, but half its body doesn't move, its legs don't work properly and, because it's not producing coordinated movements, it's quite likely that it'll move on one side not the other and end up flipping itself on its back. And this means that then it sits on its back and that's a very stable position to be in because the shell of the back of a cockroach is a nice smooth round surface to lie on, so the cockroach is more likely to end up in that position. Also it might get rigour mortis as it dies and this is where some of the muscles stiffen and extend. And so it might happen on one side of the body before the other and that asymmetric force flips the cockroach over, but then again once it's lying on its back that's a very stable configuration. So there's nothing now, no other legs, no other movements that are going to pick it back the other way so you're more likely to find them pegged out dead on their back than sitting on their legs.
Eusebius - Mary what is your question?
Mary - I believe you just answered it but I didn't hear it. What causes a twitching eye? And also, I have a second question can I ask that?
Eusebius - No there are too many. We'll take your first one for today Mary.
克里斯,你是一个很难相处的领导今天可bius. What causes a flickering eye? Well, we've all had this. When usually you're stressed or tired or you've got other things that you'd rather be thinking about and this irritating muscle twitch happens on one side of your eye. And it's so excruciatingly annoying because it's intrusive, it gets in the way. You're trying to look at someone and you know your eye is twitching. You're trying to talk at a conference or something and your eye is twitching. The reason this happens is because muscles respond to activity and nerve cells, and in your spinal cord and in your brain stem there on motor nerves. Those motor nerves send nerves out into the skin and then into the muscles underneath and the muscles have different muscle fibers, and a nerve cell talks to a squad or group of muscle fibers called a motor unit. Impulses come down the motor nerve, trigger the muscle to contract and normally the entire population of, or a large group of nerve cells that supply most of the muscle turn on and make that muscle contract in unison, so you get a coordinated movement of a muscle. Now when you get these twitches what's happening is that just the odd motor nerve cell, instead of the whole squad of them turn on, some aberrant impulses come down the nerve and they make the muscle respond a bit and it twitches. And it can happen usually when your very tired. Usually when you're stressed or when you've had too much coffee because caffeine potentiated the action of adrenaline, one of the excitement hormones, and this therefore makes you more likely to feel stressed if you've had too much coffee and this produces these aberrant nerve discharges. You can also get this if your biochemistry has gone off a bit. Chemicals like sodium and potassium and calcium are very important for the way that both the nervous system and your muscles work. And if the levels of those aren't quite right in the blood, it can make it happen or more likely to happen. But it's much rarer for those things to go wrong than for you to have sleep deprivation or stress or too much coffee which are the communist causes. The good news is it's not harmful in the long term. The odd twitchy muscle happens to everybody, happens often, easily remedied by not doing the things I've said above. So a bit less stress, a bit less coffee. Get some rest. It will go away. It's just very irritating when it's happening to.
Eusebius - Louise, is it Louise?
Louise - Morning. I had a hip replacement. I was born with small sockets with small hips but they put the large one in and I was in a lot of pain for six years. I want to know, they did they an MRI scan and they found that the muscles have been damaged, so I want to know if I do exercises, will that help build up the muscle?
Eusebius - Okay, Chris.
Chris - Yeah. I'm sorry to hear about your predicament. Normally when we sort things out with hips then it's probably one of the most successful operations that, apart from cataract surgery that a doctor can do because we do hip replacements to relieve chronic pain and we restore mobility and quality of life to people all over the world in the medical practice by doing this. So it's a real shame that it hasn't quite worked out for you but it sounds like your case might have been a little bit more complicated. This is an issue that when you need to revise surgery it can be a lot more tricky the second time. When you go into a pristine environment and put a prostheses in, it's much easier to work with than when you have to revise things because when you have to revise things you're dealing with having to get the initial revision out, there's scar tissue. There's also other changes that have reactivity happened in the area and surgeons have to cope with all that. But surgeons are bright bunch and they should be able to work this out for you. I would certainly seek an additional opinion, but usually if you have got some muscle wasting or muscle damage physiotherapy is critical because you can build up muscles and stabilise the joint with strong muscles and this will maximise your potential to remain active. But I would certainly get an additional opinion, but physiotherapy and remaining active is critical because the more muscles strength you have that you will retain that strength. But also the range of movement and that's critical too because in order to actually have good quality of life you need a good range of movement on the joint and making sure you're able to stay active is going to ensure that happens.
Eusebius - Thank you Louise. Lets go to Tim.
Tim - Hi Chris. Whenever we watch a documentary and people are in a submarine deep in the ocean they always explain the water pressure. What would happen in theory if you took a human body to those depths would it just become paper thin?
Chris - Well remember that your body is actually full of water. 60 to 70 percent of your body mass is water, so we're a big bag of water but we've also got other bits inside us that contain gas like your lungs for example. So when you're subject to extreme pressure then a number of things happen but you certainly wouldn't shrink and implode like a submarine. The reason a submarine implodes, if it suddenly catastrophically fails at depth is because it is a steel or metal shell around a whole load of air which has got the people in it, and it's the crushing of that air that causes the problem. The human body would still exist and it wouldn't shrink catastrophically under those pressures, but other things would happen. When you have excruciating pressure on your tissues things happen to gas, so you would drive enormous amounts of gas into solution in your bloodstream and that's why divers get the bends if they stay down too long and resurface too quickly because lots of nitrogen gets dissolved in the tissues in the blood - that's a bad thing. But the other thing that happens is that under these exquisite pressures proteins in your body actually change shape and water is driven into the proteins that make up your tissues and your enzymes and your cell membranes. And under those conditions the proteins don't work the way that they do at the surface. Now animals that live at these extreme depths, like fish and other things, they have evolved special strategies, either they make chemicals that go in their proteins and stabilise them and stop this happening, or their proteins are adapted so that they need to be bent and distorted by these extreme pressures in order to work properly. And that's why if you take a fish from these debts and bring it seven kilometres to the surface it dies. And part of that is because it's tissues, the membranes and the cells don't work properly because the proteins are all going out of shape. Your body would not work properly at those sorts of pressures if you were acutely exposed to them but you certainly wouldn't implode and disappear just like that. You'd you'd still be the same shape but your biochemistry wouldn't work very well.
Eusebius - Elaine wants to know on Twitter, Chris, why is it that when touching extreme cold or ice feels as painful as when you're burnt with extreme heat?
Chris - The nervous system is there to protect you, and one of the things it does is to give you a pain signal when you're doing damage to tissue. And extreme heat or extreme cold beyond the range at which tissue begins to be physically harmed so you're literally breaking cells and releasing their contents, that will trigger pain sensations regardless of whether it's heat or cold. Chemicals will do the same thing. There are chemicals that can cause severe damage to tissue, they will produce also equivalent excruciating pain. So it's actually your body warning you damage is being done to your tissue. Now the effect we were describing earlier, which is when you suck on a mint in your mouth feels cold, or you eat a chilli and your mouth feels hot, there you're not actually damaging your tissue you're just fooling the nervous system into thinking the tissue is at a different temperature and then what it really is. But actually physically exposing a part of your body to an extreme of temperature is damaging tissue. Because in the case of high heat your desiccating or drying cells, your denaturing proteins and causing cells to become destroyed - that's damaging tissue. In the case of extreme cold then you are freezing water in the tissue very fast. And though that produces lots of very sharp ice crystals that rupture your cells and make them go bang and, as a result, you're damaging tissue. So in those cases it's extremely painful to warn you don't do that. It's not a good idea.
Eusebius - Sote or Soute. Hello.
Sote - Hello. My question is science says that enery neither can decrease nor destroyed. Now I want to know, I want you to explain how is this? Does that mean we have the same quantity of energy at any given time?
克里斯-基本上是的。当我们开始universe, the Big Bang was a lot of energy and the energy got converted into matter, material. And that's because as Einstein told us e energy equals mass times C the speed of light squared so, in other words, energy and mass are interchangeable. Now when we do something we are actually converting one form of energy to another. So if I say carry a ball to the top of the stairs and then I give it gravitational potential energy because I've done work against gravity carrying the ball to the top of the stairs. The ball has taken the chemical energy in the metabolism in my body and it now has gravitational potential energy. The energy hasn't gone anywhere is just in a different form. It's now in the ball as gravitational potential. If I push the ball off the top step in the stairs it rolls down each of the steps gaining speed as it goes. It's converting the gravitational potential energy I gave it into at the end of the steps at the bottom, kinetic energy, it's moving. It's also made some air move and made some sound and because the air's moved, friction, there'll be some heating effects. All these are energy but, at the end of the day, that energy came from me, my metabolism, which actually came from the sun feeding a plant with light which photosynthesise the sun's energy into chemical energy which I then ate and ended up in my body. So you can see energy goes round in a circle but we're not creating it or destroying it. And so the big bang endowed the universe with a whole parcel of energy at the beginning of our universe and that has since some of it's turned into matter. That matter is the source of say hydrogen in a nuclear reaction which is powering the sun and that energy is then ending up in me, as I explain, to make me push my ball down the stairs. So it's quite right, the energy is being converted is not being made or not being destroyed.
Eusebius - Fantastic. Thank you for sharing your knowledge with us, Chris. We'll do it again next week.
Chris - Looking forward to it already and thanks for the great questions. Have a great weekend everyone! See you soon. Bye bye.
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