Okay, so now there's one more condition that we have to talk about. Fever. And fever, you might think, is hyperthermia, isn't it? And the answer is no, it's not. When someone has a fever it's true that their body core temperature rises. But that increase in core temperature, is under the control of the hypothalamus. So, what happens? We have, little small molecules that can be released primarily by cells of the immune system. Those molecules are called pyrogens because they have to ability to circulate through the blood, arrive at the brain, and at the brain they will have the ability to set the hypothalamic set point higher. So, normally your hypothalamus wants to maintain your core temperature at around 37 degrees C. Pyrogens will cause the hypothalamus to say maybe today 39 degrees C is a great set point, or 40 degrees C. So, the whole set point moves higher. And subjectively what will happen when that set point goes higher is you know, our core temperature may increase and we may not feel hot, as hot as our core temperature indicates we are. Or we may feel colder than our core temperature says that we are. And part of that discrepancy deals with the fact that when thermoreceptors are sensing temperature, they are sending signals to the hypothalamus, that the hypothalamus can control the reflex arc involved the thermal regulation. But some of those signals also get sent to the cerebrum, to the cerebral cortex, so that we can sense how hot or cold we really are. So for example, if we're thermoregulating normally and we go out for a session of vigorous exercise, all of that excess metabolism is going to heat our body core. Do we feel hotter? Yes, we, we generally do. We can come back home and say, oh my gosh, I feel so hot. We'll start drinking and doing other things to cool our body off, right? But when the hyporthalamic set point moves upward at the onset of a fever, even though our body core temperature may go up, we may feel cold, subjectively. And so, one of the things that will happen, if you're at the beginning of a fever, you may feel like, oh, I want to add more clothes. I want to crawl into bed and pull on the blankets. Do you know that sensation? Okay. So, because the sensation is coldness and because the body core is still not up to the hypothalamic set point range, what will we start to do? Yeah, Ryan. >> Start to shiver a little bit. >> Yeah, we start to shiver. We're going to do the things that would cause heat to build up in the body, right? So yeah, and if you have had a fever you have probably had that experience of shivering. Everybody, you'll say to your friends, is it cold in here? And they'll say, no, it feels perfectly normal in here, but you're shivering and it's a good sign that you could be getting or developing a fever. Ultimately when whatever infection it was or whatever circumstance it was that triggered the release of pyrogens, ultimately when that condition is resolved and the pyrogens are removed from the body, the hypothalamus will return to it's normal set point range, right? And so we refer to that time when the hypothalamus resets itself, we'll often talk the fact that oh, their fever has broken. And so what happens when your fever breaks? What did. >> Why don't I take this one Dr. Scanka, because it's something we see clinically quite often. >> Mm-hm. >> So you may feel warm. You may feel flushed and you may sweat. >> Exactly. Because what has happened? Your hypothalamus resets to its normal lower range, but your body core has heated up to whatever that fever level was. And so what has to happen when your fever breaks is that you implement the heat-loss mechanisms that will help to bring your body core temperature down to normal. Is it a problem to have the fever? Amanda? [LAUGH] >> It's a very subjective question. It depends on who you ask. >> Mm-hm. >> And who, what the situation is. So it's not always dangerous to have a fever. It's in, it's a normal physiological response triggered by your immune system to help your body fight infection. We worry about the same populations that you mentioned who are at risk for hyperthermia, people who can't regulate their temperature and their fluid intake well. Very young, very young and the very old and those with circulatory difficulties are more at risk for having a fever that's uncontrollable or dangerous. >> Right. Did that answer your question? >> Yes. >> Okay. [LAUGH] >> That's exactly what, what I expected to hear. And so sometimes people will be very concerned, you know, about reporting their temperature. But the reality is that as long as we have not sustained such an abnormally high temperature for too long a time, the proteins are inactivated and organ damage occurs, we're okay. And normally fevers that result from, activation of the immune system and the fighting of an infection, normally those fevers are not life threatening. And so we would observe them and certainly take care of someone who has a fever, but we would not be quite as concerned as if they were in a condition of heat stroke. >> I would add though Dr. Scanga that while, while it is okay and safe to have a fever typically it is uncomfortable. It's, it's, it's uncomfortable to feel that warm and have, or ultimately feel that chills. >> Feel that cold. >> And you can feel achy and uncomfortable. So clinicians do try to help people who are in that situation. We give them medications to try and offset some of the symptoms of the fever. We may try some cooling interventions, and it's not something to ignore certainly. It is something to, you know, talk to a provider about and, keep track of. >> Right. Great. Okay. So, we are going to, later this week, talk about assessing body temperature. And after that demonstration of how to assess temperatures, you guys will be experts on this vital sign.
