: How do humans feel temperature differences and how precisely can we feel it?
In: Biology
Your cells express receptors from the TRP family. These receptors are proteins which sit on the outside of nerve cells, and when they’re activated they start a signal which is relayed to your brain to cause a sensation. Lots of receptors work by recognising a very specific molecule. This will bind to them (through specific combinations of electrostatic charges on the molecule and on the receptor), causing the receptor to change its shape to the ‘active’ configuration, allowing ions to move through and cause the signal (think of a lock and key, where the lock is a receptor in your taste bud, the key is salt, and the door opening is you getting the salty flavour).
Some of these TRPpy bois are a bit different from ‘regular’ receptors. Rather than recognising specific molecules, they are sensitive to temperatures. At 30 degrees they’ll be closed, but maybe at 40 degree the temperature will be high enough to overcome some of the electrostatic attractions within the receptor itself, changing its shape to ‘open’ and causing a signal. Your body encodes tonnes of these receptors and they’re all sensitive to slightly different temperatures. Some are linked to cells which let you detect temperature, and some are linked to nerves which make you go ‘oh fuck that’s hot ow’, and some link straight into your reflex to withdraw your body from the heat because it’s hot enough to damage you.
As for the why – evolution. Organisms which could tell dangerous and safe temperatures apart didn’t die and reproduced, and then it got really complicated over time, then here we are.
Fun fact – chillies contain capsaicin. Rather than activating your ‘ow fuck that’s hot’ receptors, they actually bind to them and slightly change the shape, not quite opening them but making them more susceptible to lower temperatures. That’s actually why we feel the heat – it’s not that the chillies are that temperature.
I realise this ain’t ELI5 very well but I’m a scientist not a teacher. Sorry all. For further reading this is the first thing I found on Google. Enjoy – https://www.ncbi.nlm.nih.gov/pubmed/29135465/
Also I realise I’m the only one not talking about thermodynamics and why different materials feel different. But I love this shit and wanted to feel included OKAY
Your body is like a combustion engine, constantly producing heat, and you need to dissipate that in order to keep it working properly. If you are losing too much heat you feel cold, lose too little and you feel hot.
The amount of heat you dissipate through your skin depends on 2 factors, the thermal conductivity and the temperature of the material you are touching. That’s why air feels comfortable at around 21°C but water or a piece of metal at the same temperature will feel cold, as they will “suck” more heat from your body due to their higher thermal conductivity.
So what you are feeling is not exactly temperature, it’s heat loss. And your body is very sensitive to it because your internal “machinery” needs to be at a very specific temperature to work.
We notice temperature changes because our nervous system instantly reacts to regulate the core temperature of our bodies.
We have an average baseline temperature of 98.6 degrees Fahrenheit, which is caused by the basic functioning our bodies organs (contracting muscles, electrical properties of nerves, etc.) The optimal external temperature for humans is roughly 70F. When it’s 70+ the body cannot properly disperse heat, so it works harder to cool itself and therefor makes us feel even hotter. Then, the farther below 70 we go, the harder the body will work to keep itself warm because our tissues are being slowed down by the cold.
Temperature changes could mean life or death in the wild so it’s very noticeable when these changes occur to help us jump into fight or flight mode. I don’t think I could notice a temp difference less than 3 degrees, but some people might be more sensitive.
Here’s a related little fact I find interesting. We have cold receptors and warm receptors which respond respectively. But, you may be familiar with the sensation you feel when touching very hot water. It’s almost as if it’s cold and hot at the same time. This is because we have many more cold receptors than warm receptors and at 113 F/45 C, cold receptors may fire as well.
Can anyone explain why I’ve always enjoyed washing my hands with cold water, and most people prefer warm water?
what noone seems to have mentioned is how our brains interpret the signals from our “temperature sensors”.
Our brains is much more about relative change than absolute “temperature”.
You can do an easy experiment at home. Get three bowls. One with hot water (not burn hot), one with luke warm water and one with cold water. Put your right hand in the warm water and the eft hand in the cold water for a while (20+ seconds is enough iirc).
Then put both hands in the luke warm water. The temperature of the water is now of course the same for both hands but your right hand will feel “cold” water and the eft hand will feel “warm” water.
The greater the difference in temperate, the higher the rate of heat transfer. All we can feel is the rate at which heat transfers to a colder obejct(that’s cold) or when a object transfers heat to us(that’s hot). The greater the temp difference the stronger these sensations will feel!
As for how precise, in the winter I can actually feel the heat from the pilot lights on my stove when I’m in the kitchen.
Temperature can be resembled as the movement of molecules on your body. The greater the temperature the faster the movement, the lower the temperature, the slower the movement. Now fast things can strike slow things and make those faster. This is how higher temperature bodies increase the temperature of lower temp bodies. And while doing this, the movement of the faster molecules decrease. That’s how the higher temperature bodies decrease their own temp. This is how temperature difference works.
I work in Calibration and the room is tempersyure controlled to 20 +/- 0.6C. Sometimes it heats up and goes out of spec. We usually notice when it hits about 20.50C and check the temperature because we can feel it getting “hot”.
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