It is amazing what one doesn’t know. Well, what I didn’t know up until yesterday.
I watched a TV documentation about feet. More accurate, I zapped into it, when I came home late night from work. First I thought, the topic might be rather boring. And yuk, when I saw a real human foot being unlayered to the bone by a pathologist.
Feet. You stand and walk on them, in other peoples cases, they also run on them, whereas I like to take my overweight off them, whenever possible. There are bones, sinews, ligaments and some muscle, all joined together nicely to make us move and stand. Fortunately, my feet and legs, as everybody elses, are designed perfectly, always reaching the ground.
But in the end I got hooked on the programme. As they started talking about a sense I never knew I even had. It is called proprioception (roughly meaning “grasping oneself”) and is a balance system working between feet and leg muscels (and also other parts of the body) and the brain, constantly informing the brain, where you and your body parts are in space. Together with input from the eyes and the sensory neurons in the inner ear, you know where your arms and legs are, where up and down is and where you are located in relation to your surroundings. It also enables you to touch your nose with your finger or put your findertips together, even when your eyes are closed.
They showed an experiment, where a man was put on a moveable board, that gave way to every single, even the slightest, of his feet movements, so that his sense of proprioception was ruled out. He was instantly lost, getting dizzy and couldn’t tell where up and down was. Only as the board was switched off, he understood again, that he was simply standing on a board.
I thought, we had five senses, sight, touch, smell, taste and sound. I never paid much attention to how one finds one’s bearings. One just does, most of the time. And wants to forget about the few occasions, this doesn’t work so well, mainly occurring, when one had one drink too many.
But after getting hooked by the nice term proprioception last night and reading up a little this morning, I find this entire field of more senses humans have: thermoception, nociception, equilibrioception, mechanoreception and other internal biochemical receptors. Goes to show, how instructive watching TV can be.