I get that when our skin feels a certain degree of heat it triggers a pain response, but why? What is happening at the molecular or atomic level? When I hold a hot mug of coffee, what is happening to my hand?
In: Chemistry
Your body is made up of proteins, and they have to be at a certain temperature to work. When they get too hot or too cold, they “denature” and become useless which can be life threatening. So your body has pain receptors to get you to move away from the heat before they’re destroyed.
You have things called thermal nociceptors in your skin, which are proteins attached to sensory neurons that feed back signals to your brain. The protein is designed to trigger at a specific temperature – either hot or cold – and when it does a pain signal is sent to your brain.
For instance, the most common heat receptor is called TRPV1 and fires at 43°C, which is the heat pain temperature for your skin.
Your brain can decide to modulate this or ignore this, and there are different receptors at different temperatures so you’ll feel different amounts of pain as it gets hotter or colder.
In your skin, heat – the amount that molecules and atoms are vibrating – is being conducted from the hot cup of coffee until it reaches the receptor.
Related, here is Forrest Valkai, YouTube science guy,discussing how the heat receptors in your mouth are activated by spicy food presented while taking the hot ones challenge.
[if you like dumb Science videos](https://youtu.be/Q3U6G-d-a1k?si=maAfYDnhLl4bz-B9)
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