You got nerves
His painting is of a nerve with different sizes of nerve fibers. The largest ones are surrounded by myelin, shown here as black rings. The myelin serves as an insulator-the thicker the myelin the faster the nerve sends its signals. The largest nerve fibers, also called axons, send signals to our muscles to make them contract and move, and send signals from touch receptors so we can distinguish guise what we feel. The smallest, in red, orange and yellow, are thinly myelinated or unmyelinated and send pain signals to the spinal cord and brain. The unmyelinated axons congregate together I what is called a Remak bundle-named for the guy who discovered it of course. Your nerves send their signals by electricity from their receptors in your skin, muscle, joints and other tissues to your spinal cord and brain so we can distinguish multiple sensations. The nerves also carry information from the brain and spinal cord to coordinate movement. There are some diseases that affect your peripheral nerves. Diabetes can result in a loss of peripheral nerve fibers and people can lose sensation and have pain. On the other extreme there are children born without pain fibers and grow up with no pain. This is a very terrible condition and children do not learn to avoid injury, continue to use an injured arm or leg-so pain is actually a good thing. If you wand more information on this watch a documentary called Life without Pain.