The vagus nerves, lightspeed travel and peripheral night vision

Added: 2026-05-07

[00:00:00]This is a Triple J podcast.

[00:00:02]>> Hello. Welcome to another episode of Science with Dr. Carl, where this week we were joined by friend of the show, the hookup regular, Dr. Theresa Larkin.

[00:00:10]And we got into so much ground, we randomly covered dehydration a lot that popped up in a few questions, the sympathetic nervous system, and I learned that we have two vagus nerves.

[00:00:22]I'm Lucy Smith. Let's get into it.

[00:00:27]>> Dr. Carl, we have a very special guest with us.

[00:00:29]>> We're very lucky to have Dr. Theresa Larkin from Bullingong.

[00:00:33]>> Yes, >> the gong. Hooray.

[00:00:35]>> We love it.

[00:00:36]>> Now, Theresa, we've had you on the show before. You've been a regular on the hookup. And I feel like each time you walk through these doors, there's always something new that you're working on or that you're discovering. What's been happening in your world recently?

[00:00:48]>> Yeah, very true. I'm not someone who sticks down the one path. So many things to learn about. So, I'm actually doing a project at the moment, a research project that I've called the Hundred Hearts Project.

[00:00:58]>> Okay.

[00:00:58]>> And what I'm doing is traveling around to different universities who have body donation programs, which means that people have donated their body for teaching and research purposes. And I'm looking at hearts and we're mapping the arteries and the veins of the hearts, looking at variation, looking at the thickness of the walls, lots of different features of the hearts because they are so variable.

[00:01:21]>> Yeah. And when I when I teach this you know to the students we have the textbook and the textbook has one maybe two of these variations and every year the students are asking me you know where are our textbook hearts and honestly I think I've seen one out of say 20 that we've got in our uni that is a textbook heart >> really yeah so we just want to map and really show the variability because it can link to risk of cardiovascular disease the impacts of cardiovascular disease and yeah diseases of the heart and the vessels huge in our society. So, just wanting to learn more and just again the variation between people, it always fascinates me. How many variations do we think there could be?

[00:01:59]Honestly, so many. I was in Tasmania last week and we were talking about the 16 that I looked at there. They're so different and and some of them can be similar. We can see patterns of a certain heart type in terms of thickness of walls or the heart getting bigger that represent certain disease states.

[00:02:16]And so, we're familiar with that. We can see the way that the blood vessels change to try and help that. But yeah, there is just quite a lot of variability. And and again, even down there, we were like, "Oh, this is kind of like a textbook heart." And it was close to it, but still not quite.

[00:02:32]>> Cuz can you imagine when they did those textbooks hundreds of years ago, they would have just probably had one heart.

[00:02:37]>> Yes.

[00:02:37]>> Looked at that, drew that, and we're happy with it.

[00:02:39]>> Yeah. So interesting.

[00:02:41]>> Yeah. And just as an aside, uh during a normal life, your heart will pump roughly the weight of blood of one of those enormous cruise ships weighing 15,000 tons.

[00:02:52]>> What?

[00:02:53]>> Not bad, eh? Amazing.

[00:02:54]>> Oh my god. It's an important organ.

[00:02:56]>> They're working overtime. And so when you're looking at um is the term kadaava?

[00:03:01]>> Yes. Are you taking the heart out and putting it like how does that >> So most of the ones that I look at they're already out because you know even say when we teach with we call them prosections. So when I teach we might teach with just hearts on their own or hearts with the lungs so that the medical students can see all of the bits. Sometimes we leave the heart in the chest cavity but the skin's been removed. I don't do that. There's staff that are amazingly skilled at at making these prosections so that I can ask them and you know specific nerves you know we can say can you show me this nerve or can you highlight this feature of the heart so that the students can see see all the different layers because they're going to have to be familiar with that.

[00:03:42]Wow it's boots on the ground research so much to tap into with Theresa Lin 04397575 all things the human body and your regular questions for Dr. Carl. Let's start here with Maddie in Newcastle.

[00:03:56]Maddie, you've noticed something when you're eating chocolate. What's going on? [snorts] >> Yeah. So, I've noticed that when I eat chocolate, I get mouth ulcers or ulcers down my throat. And the more chocolate I eat, the worse they get.

[00:04:09]>> No, I like in your text you said, "Why does chocolate hate me?"

[00:04:13]>> Yes.

[00:04:13]>> Um, that's so unfair. Maddie Carl, Theresa, what do you reckon's going on?

[00:04:18]>> Um, how do you know you've got ulcers down your throat if you can't see them?

[00:04:22]>> Can you feel They're at the Yeah, the pain and discomfort. And they're at the back of my throat as well. So when I open up big and wide, I can see some just at the top at the back of my throat and the redness going down.

[00:04:34]>> Are they raised or are they a break in the surface like a little crater or are they just flatten?

[00:04:40]>> They're like a little crater. So very stingy, very sore, and they happen all over my mouth. So even underneath my tongue.

[00:04:47]>> What the hell? That's so unfair.

[00:04:49]>> I 100% agree.

[00:04:51]And do you like chocolate?

[00:04:54]>> I love chocolate. I cannot go without chocolate.

[00:04:57]>> Oh, I mean it seems like a classic hyper sensitivity reaction where you've got an intolerance to the chocolate, unfortunately. So, some people can have a chocolate allergy even, but this sounds like a chocolate intolerance. And what you're talking about, you know, this redness down your throat in your mouth, whether it's ulcers or swelling, that's really typical of that essentially a hyper sensitivity. So the immune system's been on alert and it's responding to to that. And in um chocolate and this is the same as in cheeses and alcohol which you know some people have sensitivities to those as well. There's something called um tyramine. So they're a kind of an amine a chemical and they can cause this effect but they also because you've got then having more of those when you're eating it. The chemicals that break that down are breaking that down rather than breaking down histamine. So this is driven by histamine and in those hypersensitivity reactions whatever it comes from we just get that swelling of the mucous membrane. So whether that's face, lips, tongues, throat, eyes, you know. So unfortunately it sounds like like that's what's going on. Have you noticed it from cheese or alcohol as well?

[00:06:03]>> Um yes, unfortunately both.

[00:06:07]>> Damn.

[00:06:07]>> So cheese has the tyram and veomite as well.

[00:06:10]>> Oh does Vegemite. So, um, does it happen with all types of chocolate or just a few types?

[00:06:16]>> Um, dark chocolate more than regular chocolate. I don't know if that changes anything.

[00:06:21]>> And [clears throat] most chocolates come with preservatives, but there are at the airport around Australia. There's shops that sell chocolates directly from Belgium and they're without preservatives and you have to have them straight away. And it's worthwhile just trying a small amount of those to see if it's the preservatives that are giving you the problem or the chocolate material itself.

[00:06:41]>> Yeah.

[00:06:41]>> And that's interesting because it's in the cocoa, the tyramine. So that's why Yeah. the more cocoa. So maybe try some lower lower um level cocoa chocolates.

[00:06:51]>> Oh, milk chocolate.

[00:06:52]>> Yeah. Which is a shame. Yeah. My favorite is dark chocolate.

[00:06:56]Unfortunately, [laughter] >> it sucks so bad, but that's all right.

[00:06:59]Thanks guys so much. I'll get on top of it somehow. [laughter] Thanks. Oh my gosh. Thanks for your question. We've got another Theresa in Mean, Brisbane.

[00:07:08]Dr. Theresa, you've given us a bit of a hypothetical. Uh, talk us through it.

[00:07:13]>> Yes. Hey, uh, morning doctors. Um, okay.

[00:07:15]So, I watch loads of Do and movies obviously about survival situations and things like that. Now, hypothetically, you're in, I don't know, even a desert or or anywhere where you've got no access to food or water. I'm assuming, you know, at this stage, we're a few days in. Um, probably dehydration kicking in as well as hunger. If you were to stumble upon a non-brand specific red cola, um, would it be better or worse for your body in this situation to consume it or not, would you become more dehydrated from the amount of sugar or would the sugar actually give you the energy that you need to keep going a little bit?

[00:07:46]>> Theresa, I'm imagining, you know, you're walking through the and there's this mirage and the Coke [laughter] is right there and you're thinking, do I drink it? What do you reckon, Dr. Theresa?

[00:07:55]>> I think water and water intake and hydration and dehydration is so fascinating. So, it is crazy that it only takes us 3 days until someone can be super dehydrated to the point of almost death, which is pretty crazy with no drinking water. This is such a conundrum because there is fluid obviously in that drink. But the problem is that high glucose, glucose is a really strong osmotic agent, which means it can pull water wherever it goes. And the more sugar that you have in a drink like that, it can actually cause dehydration itself. So it can as it travels through the kidneys, this is the glucose, it can pull water through. It can pull water out of the body.

[00:08:36]Ultimately, if you're in a dehydrated state and you have sugar, it can even pull water from cells, which is why intense dehydration can lead to neural effects. So I don't it's a really hard one as to what you would do because you'd be so craving just the feel of the fluid even in your mouth. M even morale boost I sort of thought may have been [laughter] absolutely at the end of the day I assume drinking the Coke would be a bad idea.

[00:08:59]>> Yeah, I I do think so.

[00:09:02]>> The thing you shouldn't drink is your own urine even if Bear Grills says you should because all the renal or kidney doctors disagree the amount of salt is so high that you'll actually suck more salt as Dr. T surv talked about you'll actually suck water out of your body.

[00:09:19]But the other things like the glucose, that's not really a big problem. You're actually going to take more water in.

[00:09:25]You've got a delicate balance in your body where water is crossing all of the membranes of the cells in your body. And 40,000 lers crosses each day backwards and forwards and you only need a slight imbalance to set you off one way or the other. And your body normally regulates this via hormones from the brain called vasopressin. So in the case of urine, you will definitely start generating more urine even if you are in a dehydrated state. So what you have described is the right way to go. If you are without water, you go without water.

[00:09:52]Um you stay even if there's some water there, only a small amount, you do not drink it until as long as possible, a day or so, and then you have a small amount and in a small amount because you've forced your body into a water conserving state. And with regard to the um contents of the sugar drink, the sugar doesn't really matter. It's not going to give you an osmotic action or a diuresis. You'll benefit from the water.

[00:10:14]You get a bit of sugar or fake sugar. So definitely drink the the tin of drink, but very very slowly. Eek it out as long as you can. Urine, do not drink your own urine. That will definitely bring you closer to dying from dehydration.

[00:10:26]>> You got that, Theresa?

[00:10:26]>> Yeah. Right. Okay. Yeah. Look, I'm keen for a triple J prize pack, but that's an experiment I'm not going to do.

[00:10:31][laughter] >> All right.

[00:10:33]>> Write it down. Remember, Theresa, thank you [laughter] so much.

[00:10:37]>> Thanks, guys. Bye.

[00:10:38]>> Hey, Luke in Greta, you've got a question about Adams. What do you want to know?

[00:10:43]>> Yeah. Um, my son just recently learned that atoms don't touch each other.

[00:10:48]They've got space in between. And he was wondering how we go from that to being able to identify, say, the difference between iron or water by feel. Like, how do we determine if nothing actually really touches?

[00:11:01]>> Uh, the electromagnetic fields touch. So if you got bare feet on a floor, the overwhelming majority of the flesh in your foot, it's just empty space.

[00:11:14]There's maybe less than a thousandth of 1% actual material there. Then there's empty space with the the uh electron clouds of the atoms repelling each other. And then they then push on the nerve endings in your feet of which you have, you know, at least a dozen different types. Um, and then they're repelling the electrons in the tiled or wooden floor. So, you're not actually having atom to atom touch, but you are having atomto atom interaction via the electromagnetic repulsion. And then I'll just leave you with a very clever sentence from Richard Fineman. And it goes like this. Everything is made of atoms, comma, and here comes the second part which if they're too close attract each other and if they're sorry if they're too close they repel each other and if they're too far apart they attract each other. The atoms like an inverted commas to be a certain distance apart because those electron clouds are not even. They're not equal negativity all the way around. There are fluctuating bits whereas less negative and more negative and that leads to a weak attraction but overall there's a overwhelming repulsion.

[00:12:22]>> So is there more more of a repulsion to like an iron atom than there is to something that's softer?

[00:12:28]>> Um now you're looking at it's not so much the repulsion between your skin and the material but rather the structural integrity of the skin. So of the item.

[00:12:38]So when you were to say tap it with a sharp knife blade, if you were to tap a soft, slightly rotten bit of fruit, the knife blade would penetrate and the electromagnetic fields would push apart the electromagnetic fields of the squishy insides of the kiwi fruit because they're not held together.

[00:12:55]Whereas iron has great structural integrity for various reasons. It has different crystalline forms and there's probably about half a dozen. Iron's got about three or four of them. So there's a cubic structure and then which has got four atoms on the top and four atoms on the bottom at the corners. And then you can have a body centered structure where there's another atom of iron in the middle of that cube. And then you have face centered where there's an atom of iron in the middle of each face. But they hold together with great structural integrity as compared to soft fruit.

[00:13:24]>> Awesome. Well um I'll listen back to that with my son and figure it out.

[00:13:28]That'll be great.

[00:13:28]>> Pass all of that back on to your son Luke.

[00:13:31]>> Awesome. Thank you. [music] Caitlyn, talk us through what's happening with you.

[00:13:38]>> Hi, doctors. Um, so I've got a bowel disease and I was reading and seeing somewhere that the vagus nerve can actually cause flare up. So I was wondering like what is the vagus nerve and what does it have to do with the digestive system especially with people who have like bowel diseases like me?

[00:13:57]>> Yeah, good question Caitlyn and there has been a lot on the Vegas nerves over the last few years. So, we actually have two vagus nerves, even though even I sometimes end up calling it the vagus nerve, as if we've got one, but we do have a left and a right vagus nerve that comes straight down from the brain.

[00:14:12]>> And they supply so many things. So, so many of our organs, and it looks after autonomic responses, so responses that are outside of our control.

[00:14:21]>> So, I'm sure you've heard of, you know, the fight or flight sympathetic stress response, Caitlin. It's the opposite to that response. So the vagus nerves are part of our parasympathetic nervous system which is all about rest, digest and restore. So in terms of the digestive tract and anyone with digestive issues, the big things that the vagus nerves do in the digestive tract is that they help digestion because we only really digest when we're not in fight or flight, when we're not stressed, when we're relaxed. And that allows then movement of, you know, substances through our digestive tract so that we can move them along, absorb what we need to move the right things out in our feces. And so it's really important for movement. And so if we have this heightened level of the opposite, which is the sympathetic nervous systems or high cortisol, then actually that can be associated with constipation. And so a lot of people find that they have flare-ups when they're more stressed. Whereas the vagus nerves, they're helping that. So the vagus nerves also bring information back to the brain from the gut. So about 90% of the vagus nerves are actually going in the direction of the gut to the brain. Super important in our gut brain axis. So in terms of flare-ups, probably the biggest role for the vagus nerves is that you want them to be active. if you want them to be in their most optimal conditions, which means lowering stress, lowering your stress response, you know, taking time out for mindfulness and meditation and really good sleep patterns and healthy eating and things like that. So, absolutely, the Vegas nerves are implicated. There's recent study over the last few years looking at how you can try and stimulate the vag nerves on the outside of your ear. So, there's these transoricular vagus nerve stimulation devices.

[00:16:06]>> Yeah. But the biggest things are definitely that it's I don't know if you find this Caitlyn, but if stress is a trigger, then it's doing all those things you can to lower the stress response and increase the activity of the vagus nerves.

[00:16:19]>> And the word vagus comes from the Latin meaning to wander. You have 12 so-called cranial nerves. Cranial meaning head.

[00:16:26]And you have 12 cranial nerves. And 11 of them, 11 of them stay entirely above the neck. And the vagus is the only one or two, one on the left, one on the right, that penetrates through the body and as Dr. Tru said, massively involved with the gut. But there's an article in the New Scientist about 3 weeks ago about its involvement with the heart axis and then also it's involved with that fourth brain that we have, the brain in our gut. Overall, we are beginning to learn that it is very deeply involved with our overall health.

[00:16:57]We don't fully understand it. Do not go online and buy something that promises you quantum vagus cure of everything.

[00:17:04]We're still learning about it.

[00:17:05]>> Yeah. Anything that you can do to bring your stress down like and I don't know if you've noticed those kind of cycles, but that's that's absolutely true.

[00:17:13]>> Yeah. No, that makes so much sense.

[00:17:15]Especially I find that when I'm walking it's all of a sudden I need to go to the L. So that makes so much sense doing such a mindful activity.

[00:17:22]>> Absolutely.

[00:17:23]>> Caitlyn, you and me both girl.

[00:17:25]>> Oh, [laughter] good luck with it.

[00:17:27]Hey Caitlyn, thanks for your question and for sharing your story. Uh Sarah in Mean, Brisbane, you got a question about roadkill. What do you want to know?

[00:17:36]>> Hi doctors. Yes, I do. Ever since I can remember, uh when I'm either driving or riding in a car, you know, you can see roadkill kind of coming up ahead and I tend not to look at it because I it's gross. Um, but when I go past it, just knowing it's there, I get a full body shiver or shudder through my body that's involuntary.

[00:17:57]>> I think I'm following on from Dr. Teresa here with the sympathetic flight or fight or fright or also for response.

[00:18:06]Freeze. Yeah, that's forn and freeze.

[00:18:09]And I only came across the for one. So, you're having a part of it. I'll just mention the for one because it's interesting because uh I know people involved in sexual assault and in the medical side talking to the cops and I suddenly heard of the thorn and the cops are saying what's this for thing and they said okay so you're a cop right so you're coming out of the club late at night and suddenly this person comes up and pushes a gun against your body and says give me your car do you fight them or do you fawn you give it to them yes of course you can take my car do you want my wallet yeah just don't kill me so that's part of that so you're getting a small specialized part of of it which is the the goosebumps related to when we had hair all over our bodies back about 2 million years ago. Then we had an evolutionary change. Two evolutionary changes. Firstly, we lost body hair.

[00:18:53]Secondly, we were able to put the protein that went from body hair and our brains. And so our brains started getting bigger and here we are today the peak of evolution because we invented poetry, income tax, and weapons of mass destruction. But part of that reflex we're trying to make ourselves look bit bigger. So if you scare a cat or a dog, you'll notice that the hairs go on end.

[00:19:15]>> We still have that wiring, but we don't have the hairs anymore and we've got a small number of follicles or or sort of broken down reduced follicles which give the goosebump thing. Is that kind of isish, Dr. Teresa? Yeah, I think all of that and and even just as an extension that fight or flight response, it's all about getting you primed to run and so it's it's allowing more blood flow to the muscles and so if you're in a car though and you're not able to run, you could also get this shivering because as Dr. Carl said, you've got then that extra innovation. Um but some people also might faint from something like that. And that's the next extreme of our nervous system which is still actually the vagus nerve but this dorsal part of the vagus nerve our primitive one which is related to that freeze and fawn >> where if there's danger and you just you kind of almost can't handle it or you have that phaso veagal response and that's when you can just freeze essentially or you know someone could faint or you block it out. So yeah, super interest. It's our sort of survival mechanisms going in overdrive because you you might see it and psychologically you think >> that thing's dead. You know, am I at risk here?

[00:20:19]>> Just as there are some restaurants in certain parts of the USA which specialize in serving [laughter] road.

[00:20:24]Have you had any of those?

[00:20:26]>> I I'll pass. Thank you.

[00:20:27]>> Yes.

[00:20:28]>> Oh my gosh, Sarah, thanks for your question.

[00:20:31]>> No worries. Thanks.

[00:20:32]>> And we got Sammy in Bulu Perth now.

[00:20:34]Sammy. All right. paint a picture for us. Okay, maybe you're sitting up for the night. What are your cats doing?

[00:20:41]>> So, my girl cat, Crazy Daisy, is running around. Um, doesn't really care and she'll do that all night. But my boy cat, Donnie, if just like about 3 days before my period and the first 3 days of my period, he will come in and I always sleep on my side. So he'll nudge and get into my arm, put himself into little spoon position and like purr and just like be really warm and he'll stay there all night just like wanting a cuddle.

[00:21:07]And I'm wondering whether he he knows something's going on or if there's any reason for that or whether it's just he's a lovely boy. He won't do it any other time of the month. It's just for those like six, seven days.

[00:21:18]>> Oh my gosh.

[00:21:19]>> Okay, before I hand you on to Dr. Theresa, have you written this down?

[00:21:23]>> Yes, I've been recording it. This is month number three. [laughter] month number three. Okay, we're good.

[00:21:28]>> Okay, look, if you can send us that um to triple J, what's the best address or email or something?

[00:21:33]>> Send us a a text 04397575 >> and we'll take you down that pathway.

[00:21:38]And if it turns out that you have actually recorded beautifully and we're seeing a correlation, Triple J fun pack.

[00:21:44]So, what's going [laughter] on here?

[00:21:45]Smell.

[00:21:46]>> Theresa, can you speak to this?

[00:21:48]>> Well, things do change over our menstrual cycle and so I love stories like this, Sammy. Um, so yeah, what changes that literally is real, you know, is in the second half of our cycle, >> our body temperature goes up and we have changes to our immune system because the body's thinking we could actually be pregnant. And so it's starting to prepare and it's it's making our immune system change. And so just before your period, those things then return. So body temperature drops back down. Your immune system drops back down. Some people might even get a little sore throat just before they get their periods. And then during your first days of the period, nothing's actually really happening in your body. So it might be that this particular cat is responding to the fact that you don't have higher levels of estrogen and progesterone.

[00:22:34]Your sweat might smell slightly differently. You know, your body temperature has dropped back down. There could be there could be changes. There could be pherommones that the cat's picking up on. I totally agree with Carl that probably good to see how often it happens. There are things like that that I think we underestimate what animals can sense.

[00:22:52]>> But there are changes. There are changes that happen to our sweat rate, our sweat smell over the cycle, and our temperature, and that might be enough for it.

[00:22:58]>> Wow. So, Donnie the cat is cuddling up to you, but Daisy, [laughter] the other crazy Daisy.

[00:23:03]>> Crazy Daisy. She couldn't care less.

[00:23:06]>> No, she couldn't. It was funny because [laughter] that happened the other day.

[00:23:08]My husband like turned to me and he was like, I was a bit moody as well, but he worded this very nicely, and he's like, Donnie was really loud purring in bed last night. Um, what where where are we at? [laughter] >> You're right. Actually, >> do I need to worry or >> My god, >> let me know now. He protects him now.

[00:23:26]>> Yeah, [laughter] Sammy, keep writing it down. Let's see where this goes.

[00:23:30]>> Perfect. Thank you so much, doctors.

[00:23:33][music] >> Now, Zach in meen, Brisbane, you're having a bit of a debate with someone at the moment. What's What's going on?

[00:23:41]>> Uh, hey, uh, so I got into an argument with my work friend the other day. So, is blood a liquid or is it more of like a really fine sand? [laughter] >> Wait. So, wait and hang on. Who's What side are you on? What do you think?

[00:23:56]>> I'm on the sand side.

[00:23:57]>> Okay. A liquid or a really fine sand?

[00:24:01]Theresa, what do you reckon?

[00:24:02]>> Oh, I love that. I've never heard it being described as a fine sand. So, I think that's so creative. It is definitely a liquid. Yeah. Sorry, Zach, but you know, maybe you can twist these words when you're getting back to your friends.

[00:24:14]>> [laughter] >> Um so no it is definitely a liquid but it absolutely does contain cells but we can separate it out. So when blood is taken and then put in a centriuge and it's spun the cells go to the bottom and the water component the plasma goes to the top. So you could kind you know there are cells and when you do that that part is is thicker. But yeah basically what what blood is made of is it's around 55 or so percent of blood is is plasma. And it's interesting because plasma is not produced by any organ.

[00:24:45]It's literally just the water and the salts that are absorbed from our digestive tract from what we eat and drink. Hence, back to the dehydration issue as well. You know, we we can only have our plasma volume, which is essential to get nutrients to all of our organs when we've got enough water. So, yeah, most of the blood is is plasma.

[00:25:04]And then in terms of the cells, we've got the red blood cells, which obviously are important for carrying oxygen and carbon dioxide. We've got the white blood cells which are important for immune and infection and then platelets which which stop bleeding.

[00:25:16]>> But I do you know something interesting when um we collected blood a lot in lots of the studies that I've been involved in and I've done lots of the spinning it down and it's true that males have a larger proportion of the red blood cells and compared to the plasma than females.

[00:25:30]And so you can even often tell once you've spun it down which is the males and which is the females. And that's just the impact of testosterone. And yeah, super interesting.

[00:25:39]>> Wow. And then to add a philosophical point of view rather the better way to think is that blood is an organ >> that happens to move around your body >> as said so it's an organ it does a whole lot of stuff it happens to be as said about 55 Dr. said 55% salt water and 45% all sorts of uh weird sort of stuff in there that 45% cells and you mentioned some of them. The weird thing is that the majority of the cells in your body are in your blood.

[00:26:07]>> So they're red blood cells. They're [snorts] 65 or so percent of all the cells in your body. They do not have DNA. They do not have DNA. All the other cells do. And you can have a situation called sludging which happens to people who want to cheat at a sport. And so what they do is they in cyclists will take some blood out and then separate it down and just get the red blood cells which carry the oxygen and then they'll inject it into it. So there's nothing foreign in their body. There's nothing to pick up. But instead of being 45% cells, they're 48 or 49. And actually gives them just a tiny edge. The disadvantage is that evolution has picked a reason for 45ish. And you can have sludging where they just join and compact and they clog up in your heart and you have a heart attack and you die.

[00:26:53]>> Oh my gosh.

[00:26:54]>> So don't do so don't do that reinjection of the blood cells into your body again.

[00:26:58]>> And just to add on to that so that yeah pepperon's obviously where also in your blood that's where we're carrying you know our hormones and vitamins and things like that. So yeah it's it's more than just those cells. Anything that you can measure in a blood test is obviously traveling around your blood. That's how everything gets from being made in one part of the body to another part of the body. And when you you just said anything you can measure um normally you can measure say half a dozen things in your blood cells sorry in your blood. Uh a test was done looking at people changing their chemicals in their body as they age. So they're looking at chemicals in the salt water and they didn't look for seven or so different things per person.

[00:27:34]135,000.

[00:27:35]>> Wow. Yes. Yes.

[00:27:37]>> Yeah. And they found that there's um and they gathered 250 billion data points looking at only 100 people. And they found that you do a big drop in the chemicals involved in metabolism in your 40s. So you say, "I'm eating as much.

[00:27:51]I'm doing as much exercise, but I'm putting on weight." Yep. And then you have a drop in the immune system once in your 60s and 70s. So you're more likely to drop dead from an infection.

[00:28:01]>> Zach, you might not have been right on the sand element, but you've got all these facts to take back to your workmate. Okay.

[00:28:06]>> Yeah.

[00:28:07]Okay, >> thanks, Zach. We got Melissa in Newcastle. Melissa, what do you want to know?

[00:28:14]>> Um, I was just wondering why does your skin get really really thin as you get older? So, I've noticed this especially like in my father and other older relatives as they as they age, their skin just gets like really really thin.

[00:28:30]Um, and I just wondered why and is there anything we can do to stop it going that way?

[00:28:37]>> Um, evolution doesn't care. Uh, once you've had your babies, you're over the hill. And the things that happen to your skin, there's about a half a dozen different things that happen. Firstly, you've got collagen, which is the most important, sorry, the most numerous protein in your body. It's a triple spiral rather than a double spiral like DNA. Um, and the rate of production starts dropping in your 20s. Also, you start losing elastin. That's the first thing. Second thing, you're losing the dermis. You got the epidermis. Epi means around and it's living cells and underneath that is the dermis and the moisture content of that and a whole bunch of other chemicals like glycosamines and it gets thinner and weaker. The third thing is that you're losing fat. So at one extreme look at a newborn baby they just got fat coming out of the wazoo everywhere. Um and then fourth thing you're having decreased cell turnover. Now she doesn't care about you anymore. Uh and fifth thing, you didn't care about yourself, so you didn't wear sunblockers before you walked out the door. Sun damage in Australia. So all of those things contribute.

[00:29:37]>> Yeah. Yeah. Absolutely. The biggest things are that we just slow everything down as we age. So cells develop more slowly. We don't have as good turnover.

[00:29:47]And that's why, you know, on the skin as well, apart from it getting thinner, because we have less production of the collagen and the elastin, wounds also take longer to heal. And people definitely notice that as they age. Um the wrinkles again damage just not as good turnover of the collagen and elastin and then even again dehydration it's been a bit of a topic of today the glands are less active in our skin so we've got less moisture and moisture is a good barrier you know all the secretions are a really good barrier as well and I guess to think that all of these things that are happening on our skin that we see things like that are happening inside our body as well.

[00:30:20]>> Wow. And finally, what can we do about it? The process of programmed cell death, which is the overall description of what's happening to the different cell types, is called apoptosis. Apo p o s i s, which in Greek literally means, ancient Greek, the yellowed leaves falling from the trees in autumn. But in biology, it means programmed cell death.

[00:30:40]And in the background, all the biologists and the genetic biologists and the molecular biologists, they're all looking at this saying, each of our cells has a program to die and we will find this program and reverse it. We're not there yet. Not for a while. But if there's any young children listening today, they'll be probably in the first generation to live forever. And I'm definitely going to be in one of the last generations to die.

[00:31:03]>> Wow. Well, Lisa, thanks for your question.

[00:31:06]>> Okay, that's great. Thank you.

[00:31:08]>> Thank you. And we got Caroline in Mossman. Caroline, you got a question about your vision.

[00:31:13]>> Yes. Hi guys. Um, my question is, why can I see better with my periphery when it's dark than I can with my own direct eyesight?

[00:31:22]>> Uh, this is well known to astronomers.

[00:31:26]So, you have in your you've got two eyeballs 24 millimeters in diameter by the time you're 12 years old and they pretty well stay at that. Inside is a very thin layer called the retina.3 of a millimeter thick wrapping around on the inside. It has got roughly five million cones which you use in the daytime. They don't really work well at night but they do work a little bit and you got a whole lot of rods which work better in low light. Right at the very center of your field of view is a thing called the macula. And if you want to look at somebody's face or read newsprint, you you will swivel your eyeball so the image lands on the macula. It's an area about or also called the favilla. It's about a millimeter across and the cells there are half the thickness. So they're high resolution. The trouble is they need a fair bit of light to work. So the astronomers, they can't see anything with their macula. They look a little bit to the side and the cells there are larger and they can pick up more light and they will register something. And so you can actually play this game at night where you look at a very faint star and then look off to the side and it vanishes. You can't see any field of view then you look back again. So there's that whole peripheral vision is sometimes better at night.

[00:32:38]>> Dr. Theresa.

[00:32:39]>> Yeah, absolutely. Because the rods are around the edges of the retina then actually that is and the rods are for our night vision. they can only detect shades of gray basically and so that's why we sort of can see more peripherally at night whereas the cones are more concentrated in the center that they pick up color that's more during the daylight so yeah it is really true that you can have that increased peripheral vision at night and you know the old thing about you know eating carrots to avoid blindness >> but actually vitamin A deficiency and carrots are a good source of vitamin A that can cause dysfunction of those rods cells which can implicate night blindness. So, we should eat more vitamin A.

[00:33:20]>> Yeah. Yeah. We should have a good amount of vitamin A. All right.

[00:33:23]>> But that was a myth started by the British government in the Second World War >> to get people to eat more carrots.

[00:33:27]>> Yeah. To cover up the fact that the British government was the only government in the whole world to have radar that was small enough to carry on an aeroplane as opposed to the big ones on the ground. And so they covered up their airborne radar by putting out the myth that their pilots could see better at night because they ate carrots. And that's how that myth started. Oh my god.

[00:33:45]>> And if you're at the stage where you're low in vitamin A and having bad vision, you've got so many other problems beforehand as well.

[00:33:52]>> Okay, Caroline, does that help?

[00:33:54]>> Yeah, that's awesome. Thank you guys.

[00:33:56]I'll be I'll make sure to eat lots of carrots.

[00:33:58]>> Lots of carrots. Caroline, thanks so much.

[00:34:03]>> Locky in Barin Heads, what have you got for us?

[00:34:06]>> Hey there, doctors. Um, I've got one regarding light for you. If I was traveling in a spaceship that was somehow able to go the speed of light, would I essentially be teleporting?

[00:34:21]Uh, no. It'd be completely different.

[00:34:23]Teleporting is a whole different thing which is shifting atoms from here to there without covering the space in between. But you would have a different field of view. You can't travel at the speed of light because you have mass, but you could travel relatively close to it. And just as an aside, if you could have a rocket that could accelerate at 1g for 90 days, you would reach the edge of the universe in 90 days of your time.

[00:34:49]The edge of the observable universe, 15 billion light years away. You would be traveling at close to the speed of light. You wouldn't get there. Back on Earth, millions of years would have gone past, but you would have got there in your time of 90 days. what you would see. The vision in front of you would be brighter and bluer, and behind you, the stars would be dimmer and redder. And furthermore, they'd be focused into a kind of a cone. So, you'd have this cone of brightness getting bluer and bluer.

[00:35:16]And the faster you went, the more blue it would get, and it would shift from the blue into the ultraviolet, which would become invisible to you. And correspondingly, off to the sides, the vision would be darker. That's kind of what we think your field of view would be as you travel close to the speed of light.

[00:35:32]>> Does that help?

[00:35:33]>> That does help. So yeah, not quite teleporting.

[00:35:37]>> Not quite teleporting.

[00:35:38]>> Definitely not.

[00:35:38]>> Sorry, Locky. We've got Tilly and Marubra. Tilly, what's your question?

[00:35:43]>> Hi, I wanted um to know um the health benefits of bone broth and what it can do for you.

[00:35:50]>> Theresa, yeah, bone broth is good for us and I love that it's something that's sustain sustainable. you know, people were using the bones, they've used the meat, and they're now going to use the broth. So, yeah, it's actually got some lots of really good things for it. So, it's got it's good source of protein.

[00:36:04]It's got some nice amino acids, amino acids, and these are all important for muscle and, you know, hormones and things like that. It's got good minerals, so calcium, magnesium, potassium. If people add vegetables that's in, it's really good. And I think also because it stews things in that liquid, the nutrients stay within it without obviously if you overcook vegetables, you lose those. But yeah, it absolutely leeches out things from the bone that are really important for us that are healthy in us as we are, but to gain those from consuming them is really good. It's a good source of water. You just have to be make sure that it's not too salty. Okay, great. Thanks, Tilly.

[00:36:41]>> Thank you.

[00:36:42]>> And we got Alicia in Newcastle. Alicia, what do you want to know? Last question.

[00:36:47]>> Hi doctors. My question is how heavily is the moon linked to periods? I seem to always get my period on a full moon like clockwork, but then on top of that whenever it's a super moon or some kind of special moon, my symptoms are heightened or intensified.

[00:37:04]>> Is this common or why does this happen?

[00:37:06]>> Well, maybe you're just your 28 days are just completely aligned with the 28 days of of the moon. So, you must be someone who is super regular on that essentially the definition time of of a 28 day period. And then if you're staying on that cycle, it just must be aligning with the moon's paths. But yeah, not sure how a super moon can affect that as well, Carl.

[00:37:27]>> Right. Have you been I know I was boring been writing it down, making notes of this.

[00:37:34]>> Yes and no. Whenever I feel like my symptoms are more intense, I look up on the internet and then it's always seems to be some sort of a special super moon.

[00:37:44]>> Not quite counting for a triple J prize.

[00:37:46][laughter] But it is interesting and I do believe that only a very small percentage of women are very very regular cycle. So you you might have had that regular cycle then clock in on the moon.

[00:37:56]>> But I love that this brings in astronomy and the human body in >> will not be happy that I'm linking [laughter] that to that. Write it down.

[00:38:05]Write it down.

[00:38:06]>> Alicia, thanks for your question.

[00:38:09]>> Thank you. Oh my gosh, it always goes so quickly. Dr. Theresa Larkin, thank you so much for hanging out with us, answering our questions. If we want to find out more of your work, where should we go?

[00:38:19]>> So, I'm Dr. Theresa Larkin on Instagram.

[00:38:22]That's probably the best starting place.

[00:38:23]>> Amazing. Well, we'll catch you next time. So much for hanging out. Dr. Car will do this again next week >> with a special guest >> with another special guest at the wazoo.

[00:38:32]We can't wait.

[00:38:34]And that's it. Thank you so much for joining us for this week's episode of Science with Dr. Carl. And a big thank you again to Dr. Theresa Larkin for joining us. We'll pop her details for you in the show notes. And that is where you will find our new spot for you to send through your Science with Dr. Carl questions. Of course, we always take them live on a Thursday via the text line. But if you've got one and you want to submit it right now, you can do so via our new Google form. Just tell us who you are, where you're from, what your question is for Carl, and whether we can give you a ring at some stage so you can be on a future episode. We want to get you on there. So, if you've got a question, let us know via that form. I'm Lucy Smith. This episode was produced by Josh Brennan, and we'll catch you next week. Bye.

[00:39:17]Dave Maresy here from the Triple J Hack Team. Hey, if you love Dr. Carl's podcast like I do, you might enjoy the Hack Podcast as well. Each day we bring you the news that matters to you. From the latest science on climate change to what's happening in politics and news around the world. The Hack Podcast. It's your daily fix of the news you need to know. Get it wherever you're listening