Incredible coloured scanning electron micrograph (SEM) of section through a human spinal nerve.
The nerve is composed of numerous bundles of myelinated axons. In the centre is a blood vessel filled with red blood cells.
The human body contains 31 paired spinal nerves.
The spinal nerves connect the brain/spinal cord with the muscles of your body.
If you want to move your leg, your brain sets the impulse, the signal goes down your spinal cord until it reaches the lower segments.
There it gets switched to a so called “motor neuron”, which leaves the spinal cord and leads to the muscle. The signal activates the muscle and it contracts. That’s how we run marathons, give each others hugs and do everything that makes us move
Image by Thomas Deerinck via Daily Anatomy