How does the human body maintain approximately 98.6F? It is easy to see how temperature can come down but where does the heat come from when ambient temp is much lower? What is the source of heat in humans? I know about differences between warm blooded and cold blooded. What generates the heat in warm blooded creatures, specifically humans.
I assume, perhaps, that the commonly held belief is that food, working as a fuel source, and possibly digestive processes generates heat but is that true? I dont think so.
Our body is only about 20% efficient, so 80% of the calories we use go towards generating heat. Usually, this heat is simply waste, but when it's cold outside our body attempts to keep more of this heat by constricting peripheral blood vessels, "goose bumps" (intended to fluff up fur to hold more heat), and shivering which increases your metabolic rate from a base for a sitting person of 50 Cal/m 2 hr to about 250 Cal/m 2 hr.
I haven't seen it until just now. The first method is simply to increase the rate of metabolism (besides reducing perspiration, which is the actual first). The second is to reduce the amount of blood flowing near the skin. And if the temp drops too much, involuntary shivering starts.
All the information we can obtain the better. I am asking specifically about the heat source whereas the methods of maintaining body, temperature is interesting albeit secondary. For reference think of a wood stove. Please Register or Log in to view the hidden image! The stove is cold and it just exists. You take a few pieces of wood and you throw it into the hole, arrange it in a way as to facilitate combustion, specifically in a way as to maintain combustion for the usable lifetime of the wood. Once the fire begins you feel the stove gradually getting warmer. When the fire is blazing and the apex of heat radiation is achieved the stove becomes extremely hot. As the supply of fuel is exhausted the stove reflects this in a lowering of temperature. When a human walks into a room with a temp of 72F the body maintains it's temperature of 98.6F (or around that). If the temperature of the room fluctuated withing a range of 40F the temperature of the human will remain constant. The human stays in this room (really a small living space) for days and maintains it's temperature even with varying amounts of food intake. Taken to an extreme the subject will now forgo food intake for a prolonged period of time AND the temperature in the room will remain a constant (consistant) 65F. Of course the first response of the reader will be 'the subject will shiver and maintain it's temperature that way'. Of course, however, that is NOT the question. What I am asking is what physical process produces the 98F body temperature.
Here is something i found: http://hypertextbook.com/facts/LenaWong.shtml I will continue to add links that may be even more pertinent in relation to my specific question.
Obviously human (or other animals) can maintain their body temperature because there are heat production inside the human body. You are asking about the heat source? You might be interested with a topic of thermoregulation, which is the ability of an organism to keep its body temperature within certain boundaries, even when temperature surrounding is very different. The heat is mainly produced by the liver and muscle contractions, but that is not the only heat production process. Any 'mechanical' activity including thinking produce heat. Actually, the heat itself is a heat loss, which is the conversion of mechanical energy spent in activities into heat. The source of energy itself is mainly from food. For example, by consuming carbohydrates you can get 4 calories of energy per gram. So in short the process is more or less: Food intake ---> food cooking (metabolism) ----> mechanical activity (thinking, breathing, moving, etc) ----> heat loss (preservation of body temperature)
Thank you. I will look at the link but do you have an answer? What is the heat source? 98F is relatively hot.
Let me say that the only organ i can think of that may radiate heat is the heart. Obviously blood alone will not produce heat but acts as a conduit and perhaps a heat exchanger, specifically it flows through the veins while reacing the outermost extremities becoming cooler\colder (losing temperature). This is especially evident in low ambient temperature.
I'm not sure if I can do the calculation, for sure there are other people that can. The conversion of energy content in a food into heat and then into temperature, I mean. To maintain the temperature, we are continuously consume food. The further mechanism to keep the temperature constant itself can be found in that link (but citation is needed): It's about my lunch time, btw. Then I have to do something. Later!
That does not seem to be correct. The reason i say this is that assuming food as a fuel source then wouldnt there be a corresponding loss of heat or increase in heat with the amount of food intake? As i said previously, taken to an extreme and doing without food (fuel) there is no gradual lowering of heat. Even at the point whereas the stomach contains no food.
I've answered your question COMPLETELY. John, do you honestly NOT know what the word "metabolism" is and means? If not, read about it in Wikipedia - evidently, you've got a lot to learn about the subject.
john as read only and mad have said the heat in the body comes in the form of in efficencies in ATP usesage and possable its creation. Futher it heat can be formed from ambient suroundings in the form of ingestion of hot liquids ect. Lastly friction itself in the joints and musles produces heat. I disagree with Mad that its an unintended process. Rather, regulation of heat is very important for the body. For instance emzimes have a specific temp where they will activate or work to there optium. If this temp isnt maintained the emzimes dont work or (if to high) they denature. This is why the body produces fevers, bacteria are less protected than the cells of the body and there for by boosting the heat the body can denature the protines and emzimes of the invader or even cause them to premiturly activate causing digestion of the bacteria itself. Not the most precise method maybe but a method nun the less. Further mechanical digestion itself can produce heat from the many chemical reactions which take place in the gut Lastly the body is full of chemical reactions apart from just ATP construction and use (fuel load for want of a better term), pH reactions for instance produce heat as a bi-product and these happen all the time in our bodies. As to how we keep it in thats easy, fat is a VERY poor conductor of heat. This is why fat stores (atipose tissue) are near the skin (sub cut) for the main. The skin's capillary bed flows ABOVE the sub cut fat cells, this alows the body to decide to send blood to the skin in order to radiate it away (as well as convection and conduction). If, however it wishes to CONCERVE heat it diverts the blood surplie away from the superfical cap bed and there by forces the heat to travel through the adipose tissue to escape. As this is hard to do the heat is conserved in the body
Asguard, are you saying that your belief is that food is the primary or main factor in producing heat in the human body?
The food is the fuel, John - it's just as simple as that! Food is broken down by digestion inro simple sugars like glucose - and the body uses that for energy by 'burning" (oxidizing) it. The process produces heat as a byproduct. Surely you understand what oxidizing does to a substance.
The temperature is close to 100F, which is pretty high. The stomach empties of food after approx. 3.5hrs. Nine hours later and the body shows no signs of temperature variance.
Of course! The temperature is regulated by activity which in turn is regulated by the hypothalamus gland. You should read up on that, too. Tell me - and be honest - are you actually reading ANYTHING I've been suggesting or are you just blindly continuing to ask questions while putting forth no effort of your own???? If you aren't too lazy to do so, read THIS: http://thalamus.wustl.edu/course/hypoANS.html
