ELI5, what is proprioception
It’s your body’s sense of where it is in space. Proprioception is what lets you touch your nose with your eyes closed and know how high to lift your foot when climbing stairs without looking. It uses proprioceptors, which are neurons in your muscles and tendons to figure out the relative positions of all your parts.
It’s all of the many senses that, used together, help you know where you and all of your limbs are. If your body rotates forward or to the side, your inner ear’s vestibular organs will sense it. If someone bends your arm, your skin and muscles will sense it. If the horizon moves, your eyes see it. Your brain takes in all of these signals and combines them into a picture of how you’re moving and where all of the bits of you are. This means that when you stumble, you can throw out a leg to catch yourself because your brain knows roughly where your foot probably is, how you’re angled, how far you’re falling, etc.
And let me just add to the previous answers, that proprioception is one of your senses. As has been discussed elsewhere, if you were taught ins school that we have five senses, that is a lie. Balance is another one, and is closely tied to proprioception.
Interesting personal note, one in a long while when I let my mind wander, my proprioception sometimes blanks out. It’s like a panic moment… “Where the ell is my left foot right now??” Happens rarely, mostly when I daydream. I wonder if it happens to anyone else.
Oh, and read Oliver Sacks books, especially “The man who mistook his wife for a hat.” He’s a neurologist and very entertaining author, and he writes about cases where the normal parts of our brain go wrong or are damaged by a stroke, for instance.
I love watching questions coming up that stem from other posts and / or the replies therein.
Knowing where your limbs and body parts are and what they are doing at all times without having to think about it.
If you close your eyes, and then someone asks you to use your left hand and touch your right foot, you will be able to do it without looking. You can do that, because of proprioception.