Blame the vestibular system – the sensory system that perceives our motion in space in relationship to gravity. The sensors themselves are located in the inner ear, but the information they provide is critical to perceiving and maintaining our vertical alignment with gravity as we move around in the world.
And that matters for more than not falling down. Gravity affects every breath we take, every move we make (not to mention every cake we bake) whether it involves the muscles of the heart, breath, and digestion or the skeletal muscles that get us around in the world.
Vestibular sensory signals don’t just hook up in the brain with movement systems that keep us upright; they participate in the control of digestion (not surprising in that dizzy often goes with queasy), breathing, and the cardiovascular system.
And that’s not all. Making sense of input from our “sensor array,” that is, the eyes, ears, and nose, requires info about the head’s motion and alignment with gravity. That’s why “dizzy” makes the room spin, as it messes with our visual perception of space. We need accurate vestibular input for the brain to weave together a stable sense of space.
We remain blissfully unaware of the involvement of our inner ear sense-of-motion in how we see and navigate the world, let alone in how we digest our lunch, until something upsets our equilibrium. Only then does this remarkable sensory system come into view.