eli5 How does localisation of sensation work? Do the nerves have to be in the right spatial location or is it more an illusion?
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Each finger tip has over 3,000 touch receptors. (We have way more in our feet).
We can feel objects down to 13 nanometers with our fingers. A sheet of paper is 100,000 nanometers thick for reference. Another example from google is if our finger tip was as big as the earth we could feel the difference between houses and cars.
Touch is kinda an illusion but also not. It’s a force from electromagnetism. We have many different nerves and neurons in our brains that are responsible for a lot of the senses and they of course like to work together in one big system called our Nervous System.
Merkel cells found right beneath our epidermis which is the outermost layer of skin is what is responsible for our ability to recognize fine and sharp details in touch. They are at the very tips of the receptor that is responsible for touch.
We kinda just have so many nerves and cells working together that it creates a giant map all over our bodies.
Hope this helps
The nerves that link a finger to the brain is a bit like a wire it literally carries the signal from one end to the other. The brain knows which nerves travel to which location so knows that an electrical signal in that nerve means a particular place on the body is sensing something. There is a thing called dermatomes which form the end points of the nerves at the skin that does the sensing and the pathways of those nerves to the brain is known and forms a map of the skin.
The nerve that goes to your leg for example enters/exits the spinal column in a particular place before carrying the signal to the brain. If there is a problem at that spinal joint you can get what’s known as referred pain, where the brain thinks the leg hurts when the nerve is actually being pinched in the spine.
So sensing is very much geared to the entry point to the brain, when the electrical signals reach the brain does it’s best to guess what’s going on by which nerves are being are carrying a signal, the brain is good a guessing but can get it wrong.
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