"What tells you your bladder is full? Your body uses a sense that is so all-pervasive it’s normally kept at a subconscious level so we aren’t overwhelmed with information. Sometimes referred to as a sixth sense, this internal sensing ability is actually part of the “mechanical sense” that includes touch. It tells you where your legs are and whether they are safely touching the ground; that your shoulders are connected to your arms, and so on."

Image Credit: Madhero88 and M.Komorniczak - https://en.wikipedia.org/wiki/File:Skin_layers.png, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=21986708