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Uno Dos of Trace: How Does Your Body Know What Temperature to Make a Fever?

5 minutes

Most people are well aware of the horrible that comes with the flu. The sweating and the shivering, the fever, the being so hot that you just die and you just want to die and you just don't want to live anymore because you're sweating, but you're also cold. I hate the flu. What most people might not think about, though, is how your body knows what temperature it is inside. Also, how does it adjust that temperature once it knows it? So you may not be surprised, but I have some questions.

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Hello, everyone. Thank you for tuning into Uno Dos of Trace this week. I am not going to miss a week even with a 103 degree fever, which I almost hit. My temperature over the last week was hopping all around, from the low 100s to the, well, also low 100s. But still, it was crazy! I was stuck on the couch, which you can't see it, but it's right there. And I was just shivering, and shuddering, and it was the worst, and then I would start sweating and then my girlfriend would be like, ew, you're gross. And I was like, oh, I don't even want to be around myself. I would crawl into bed under the covers wearing two sets of sweat pants, big fluffy socks-- the best-- a long sleeve shirt and a hoodie, and I would still be shivering. Or I'd be out here in the living room sweating like it was summer in the DC Metro area. It was just humid, it was disgusting. Our cells don't have thermometers tucked in their little tiny cell pockets. So how do they know how hot or cold it actually is? Well, first, animal cells all have TRP ion channels, and each channel triggers at a different temperature. So even though I just said they don't really have little thermometers in their a little cute cell pockets, what they actually do have are these. Each of these TRP ion channels trigger at a different temperature. Once it's triggered, the cell knows exactly how hot it is and it reacts mechanically, really, to what has happened. So that's how we know how hot it is, but how do we know how hot to make it? Body temperature starts and ends in the hypothalamus. It's the main control center of thermo regulation of the whole body. It does other things as well, but that's its function as far as we're concerned today. Like everything in the body, it's a lot less inside out and a lot more Rube Goldberg. So let me give you an example. Fever is set off when the immune system senses tissue injury and produces something called a pyrogen compound. It gets into the blood where it gets to the hypothalamus. From there, it excites the cold sensing neurons and inhibits heat sensing ones. It's like they flip this one specific switch and up regulate the temperature of the whole body. Pyrogens can be produced by the invaders themselves, as well. So our internal systems did evolve to know what these compounds mean. It means invasion. And to fight invasion, the body's going to heat up and make itself less friendly to pathogens. Also, less friendly to your conscious self and your partner, who may think you know there was maybe a social agenda today. No, apparently not, because I'm disgusting and dripping with sweat. Sorry, sorry, baby. So to act on that order to make it hotter, the hypothalamus has several strategies. It can tell the skeletal muscles to shiver, which is annoying but it burns energy and it creates warmth. It can trigger vasoconstriction, where blood vessels tighten and constrict causing them to lose less heat out of your skin. This is also why you look pale and feel cold to others when you're sick. It can also stop you from sweating or start you sweating if you're too hot, and it can release adrenaline compounds to make even more heat. Once all this starts, the body's going to get warmer and the temperature is going to fluctuate as the body responds to the existence of the invaders and the immune systems contact with their little invading bits. For me, I feel like this is a lot more of a mechanical process, feels less nebulous and makes me feel, well, still disgusting, but a little bit less bad about it. What about you? Once you've beaten back your personal wave of pathogenic pals, your hypothalamus isn't going to have that signal anymore to fever up. So it resets the internal temperature back to normal, which is 37 Celsius or 98.6 Fahrenheit. And, of course, that means the body has to cool off, which is why I was so sweaty this week, and probably why I'm sweating literally right now. Ugh. It was terrible. Anyway, one last bonus fact, before we wrap up this edition of Uno, Dos of Trace, TRPV1 is a TRP ion channel that senses spicy in your mouth and elsewhere, by the way. Capsaicin actually tricks the ion channel into thinking that it's hot when it's actually not, and your body literally can't tell the difference. It's like it's hacking our internal thermometer. Isn't that awesome? Special shoutout to Science Sam for sending me some studies when I got stuck in the middle of this thermo regulation station. Love you, girl. Thank you so much. And I know this was a shorty. I'm still recovering, and I'm going to be writing the next Seeker Plus as well. So much to do. Anyway, I better get moving. I love you all. Thanks for watching Uno, Dos of Trace. Please share, and subscribe, and I love you, and thank you.

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I feel like Superman when he fought Sunman, just under a blanket, sad. Bleh. I'm sweating right now.

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--ever in, you know, done other things that I could brag about, but my addled brain isn't going to be able to tell you about them.

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Host Trace Dominguez discusses the science behind getting a fever when sick. Fevers are integral to effective immune responses and ensure the immune system takes appropriate action against the offending virus or bacteria. Part of the "Uno Dos of Trace" series.

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