Unraveling the Mystery: How Do We Sense Heat?

[Vinay080]

Does the kinetic energy of molecules make us feel a substance to be hot? I want to know the mechanism through which we feel something to be hot.

How the molecules come in contact to our skin molecules and interact with them to send message to our brain through neurons? How the brain atoms interpret it as hot? and finally how this whole meat feel it to be hot?

I want to know about this, for the sake of discussion going on, in Physics section and mainly in my way to understand humans as either just robots or something different.

I don't have Bio-background, I would also like to know the fields which I should look for. Thank you.

 

[DrClaude]

You can look up thermoception on Wikipedia:

The details of how temperature receptors work are still being investigated.

See also https://www.physicsforums.com/threa...-we-say-something-is-hot.647634/#post-4135818

 

[Doug Huffman]

The sensation of hot/cold is the sensation of thermal energy flow rate, direction and magnitude.

 

[256bits]

Physics section and mainly in my way to understand humans as either just robots or something different.

Why the distinction?
It can be conceived that a mechanical robot could be constructed with appropriate sensors and emulate a response the same as a biological entity.
The difficult part would be the surface sensor density and performing the cognotive response ( which for biology may not be the repeatable or same for different units).

Some sites that may help you out,
http://neurophysiology.ws/receptors.htm
which describes the receptors in the skin and response to stimuli.

And more on thermoreceptors,
http://www.scholarpedia.org/article/Thermal_touch

I would think that the sensors do not just respond to just kinetic thermal energy, but rather to radiant energy and total thermal energy conducted to/from the skin.

 

[Ygggdrasil]

Although it is very different than how we sense temperature, bacteria are also capable of sensing temperature through RNA thermometers. These are RNA structures whose thermodynamics of folding are tuned such that they adopt a specific structure at low temperature which breaks apart at high temperature. These RNA structures allow the bacteria to block the production of the proteins they encode at low temperature, but then rapidly produce them at high temperature (many of these RNA thermometers are on RNAs encoding "heat shock" proteins that help cells respond to the stresses of elevated temperatures). For more information see http://www.nature.com/nrmicro/journal/v10/n4/full/nrmicro2730.html

 

[Jinamgo]

Sensory neurons called thermonociceptors are responsible for the sensing of temprature in the peripheral skin. Neurons express thermotransducer proteins such as TrpV1 or TrpM8 which change conformation and allow the conduction of an action potential when a threshold temprature is reached.

Interestingly, capsaicin (the active ingrediant in red hot chillipeppers) Binds and activates TrpV1 (transient receptor potential vanilloid 1) causing that hot sensation when you eat a phaal curry. The name TrpV1 is named so because hot chillis come from the vanilla pod family of plants, hence the name vanilloid 1. The TrpM8 receptor (transient receptor potential member 8) binds Menthol, and results in that cold sensation when you eat chewing gum.

https://basicscience.ucdmc.ucdavis.edu/zheng_Lab/images/research/Figure-1-big.jpg

 

[Ygggdrasil]

As Jinamgo mentioned, the TRP channels are some of the main proteins responsible for sensing temperature in thermosensory neurons. These proteins are ion channels that switch between an open conformation that allows ions to flow through and activate the neuron, and a closed conformation that does not allow ions through. The open-closed equilibrium of these TRP channels changes dramatically with temperature, and it has been proposed that this is due to the exposure of hydrophobic residues during the conformational change, which associates a large ΔC_P with the transition (see http://www.pnas.org/content/108/49/19492.full for a more complete explanation). This model has quite strong support because it has allowed researchers to re-engineer a non temperature-sensitive ion channel into one that responds to temperature.