Hot answers tagged

30

In the periphery (e.g. on our fingertips), our body senses external temperature through nerve terminals, expressing certain TRP channels. These are ion channels that are sensitive to temperature (note that TRP channels can be sensitive to several things, such as pH, light, and stretch) and allow entrance of cations in the cell when the temperature is higher ...


23

Hypothermia (when the body is too cold) is said to occur when the core body temperature of an individual has dropped below 35° celsius. Normal core body temperature is 37°C. (1) Hypothermia is then further subdivided into levels of seriousness (2) (although all can be damaging to health if left for an extended period of time) Mild 35–32 °C: shivering, ...


16

Short answer Birds emit infrared. Background Objects with a temperature higher than the background emit detectable infrared (IR). Endothermic (warmblooded) animals keep their body temperatures at around 37oC and given the relatively cool temperatures at the earth's surface, endotherms generally emit more IR than the background. Endothermic animals include ...


14

To complement on nico's answer (I don't have enough rep to comment), TRP channels seems to be also sensitive to increment or decrement of temperature as reported recently in a paper by Gallio et al1. Probably that channels have incomplete adaptative behavior that make them sensitive both to increment and absolute temperature values. [1] Gallio M, Ofstad ...


8

As Rory explained, internal body temperature needs to be highly regulated. Sweating is the main built in mechanism for removing excess heat from the human body. According to my biology book, in (100%) humid conditions humans cannot survive in heats of above around 45C, but in a dry environment can survive in heats of over 100C just through sweating.


7

Factors that can lower body temperature: low environment temperature low metabolic rate hypothyroidism I couldn't find any relevant study addressing the Japanese people situation, but: There is significant variation in metabolic rate in humans, independent of differences in body size, body composition, age, and gender. Although it has been generally ...


7

Homeothermic multicellular organisms have special tissues that burn resources to warm up (usually this involves breaking the electron-transporting chain at the final stages of respiration to transform all chemical energy into thermal energy). And they have special tissues (fat) and enough body mass (this is more about the volume/area ratio) to keep this ...


6

Short answer Humans sense temperature differences. Background (Including edits based upon comments) Because the question is "Do humans perceive temperature or heat-flux?", I will answer the answer from a psychophysical perspective, i.e., by dealing with sensory awareness. Just as with many other sensory systems, temperature sensors in the human body ...


5

This is the modified answer in response to the discussion: Facts: There are warmth and cold receptors in the body at two places: The Peripheral receptors and the Central Receptors The peripheral receptors are present in skin and the central receptors in the body core at multiple sites the notable site being the hypothalamus The Temperature receptors have ...


5

Short answer Water of 180 oF (82 oC) causes immediate scalding (thermal burn wounds). Background The severity of a scald injury depends on the temperature to which the skin is exposed, and for how long. Residential water heaters warm up tap water typically to 120 oF (48 oC). At this temperature, the skin of adults requires an average of five minutes of ...


5

You constantly generate heat from metabolism. The ability of this heat to be transferred to your surroundings from your skin is tremendously different in air vs. water. This is known as thermal conductivity. The ability of water to remove heat from your skin is roughly 24 times that of air. See list of materials and their thermal conductivity rates here ...


4

Flux is defined as amount of heat transferred per unit area per unit time. Our body does not perceive heat flux. It perceives temperature and tries to adjust heat exchange mechanisms until thermal homeostasis is achieved (in all warm blooded animals). This is a feedback controlled process. If it were to measure heat flux then the body cannot sense if it ...


4

A very basic model of virus inactivation is exponential decay. You can describe exponential decay with the $N(t) = N_0e^{-\lambda t}$ equation, of if you want to use half-time, then with the $N(t) = N_02^{-t/t_{1/2}}$, where $N$ is the value which reduces by time, $t$ is the time, $\lambda$ is the exponential decay constant and $t_{1/2}$ is the half-life ...


4

This due to a phenomenon called "cold shock". This induces a number of physiological changes in the fishs metabolism and also in its behaviour and can lead to death. The first paper cites some reasons in table 1: Brain and central nervous system response: Changes in neuronal activity Catecholamine and corticosteroid response: Release of hormones due to ...


4

This paper actually goes into the whole history of organ transplants. In short it seems to have the following effects: preservation - usually with a specific solution to help. slows down extracorporeal ischaemic damage slows down hypoxic damage slows down the metabolism (energy consumption) and thus the need for oxygen that blood provides. Remember ...


3

Gains heat; humans are not particularly well-adapted to make use of heat as an energy source. In a simple matter, if something you eat is hot when it goes in then the average temperature of the body has increased. More relevantly (and to get this more on-topic for biology), eating anything will generally increase your body temperature, as in order to ...


3

As far as I know, the main challenges the plants have to face in cold environment are metabolism reduction and membrane fluidity. If the temperature is even lower, they may face freezing. Increasing the metabolism is quite hard, because plants usually are unable to increase their temperature by its own. Plant may produce more pigments in order to absorb ...


3

This temperature range would be a compromise between a very low temperature needed to limit natural decay or decay triggered by micro-organisms (the lower the temperature, the lesser the decay) and the formation of destructive ice crystals. Only pure water freezes at 0°C (32°F) under atmospheric pressure. But the content of apple cells and cell walls is a ...


3

The fingers and toes (for example) ARE at lower temperatures than the interior of the torso. It's why it's so easy to get frostbite on the extremities. As for temperature regulation of the testes, you have to also consider that humans evolved without clothes...i.e. The testes just "hang out" and get lots of airflow, as opposed to modern times, when they are ...


3

I've found a good resource for this--an open-access review by Nakamura, "Central Circuitries for Body Temperature Regulation and Fever." In it, the author provides a nice summary figure of the circuitry involved in temperature regulation (see below). As I suspected, the hypothalmus is pretty central to temperature regulation. I had forgotten about the ...


3

I am assuming that you are referring to a baseline human cooled to a core body temperature of 30C from birth. I am also assuming that you are ignoring the fact that the environmental temperature (and thus the temperature of the extremities) has to be much lower than 30C to cause a core temperature of 30C. Thus, I am ignoring hypothermia-based gangrene, ...


3

Comparing Biopython MetlingTemp to other calculators. I have written the recent version of MeltingTemp in Biopython's SeqUtils. I have extensively tested the Tm calculations against other programs like MELTING and Primer3Plus and other online Tm calculators with consistent results, thus I'm pretty confident that there is no gross error in the module. The ...


3

Dinosaurs is a very broad term which includes both the ancestors of birds as well as modern reptiles. But that analogy stretches as far to say that a bird is a modern dinosaur and a reptile is a modern dinosaur but a bird is not a reptile. Both of their ancestors lived during the cretaceous period and tend to get lumped together. Another analogy would be ...


3

Sorry for the delay, I was low on time and didn't want to post a poor answer. Let's get into it step by step. The most important thing here is to understand that every single thing you do is a combination of many highly complicated biochemical and biophysical reactions/processes that slow down as temperature gets lower. Since any chemical reaction is a ...


3

Here is a good article on the topic. https://www.nlm.nih.gov/medlineplus/ency/article/003227.htm But it's most likely due to the fact that a sun burn is an actual burn on the skin that can cause inflammation, inflammation can in turn cause fever. Also having a really bad sunburn can open you up more to the possibilities of skin infections. If this happens ...


2

Some 200 years ago Dr.Charles Blagden, then secretary of Royal Society of London, went into a room that had been heated to a temperature of 126 degree Celsius ( 260 Fahrenheit) , taking with him a few friends , a small dog in a basket and a steak.The entire group remained there for 45 minutes. Dr.Blegden and his friends emerged unaffected. This ...


2

Yes, we can survive temperatures above 100 F (38 C) but surviving such temperatures requires continuous fluid intake. Since sweat evaporates quickly in an arid (dry) environment we tend to be unaware of how much water we're losing. This leads to heat exhaustion, then heat stroke, then death. Survival time depends on how well hydrated you are and whether ...


2

I do not have a source for the following as it was taught to me in neuroanatomy classes, the explanation given for brain freeze is that it is referred pain through the trigeminal nerve. The meninges (the tissue lining the central nervous system) is innervated by the trigeminal nerve in the head. Therefore the pain feels as though it is like a headache from ...


2

The discrepancy can be partly explained by where the temperature was measured from since the human body temperature ranges from 36.5 and 37.5 °C. For example it is 36.8 ± 0.4 °C when measured under the tongue (http://en.wikipedia.org/wiki/Human_body_temperature). Additionally The body temperature of a healthy person varies during the day by about 0.5 °C (0.9 ...



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