From kindergarten, childhood, media and social norms, it is likely that you were taught of the 5 senses. Including the 5 traditional senses of sight, smell, hearing, touch and taste. However, what you weren’t told of was the other available human senses. We’re not talking about some supernatural sixth sense, but rather other abilities that are consciously (and not unconsciously) used routinely and ordinarily. What we take for granted aids and allows us to survive in primitive and modern life.
The sixth sense of today will be equilibrioception or the sense of balance, this is the physiological sense that prevents youfrom falling over while running, walking jumping, standing or even sitting. Balance is made possible with a combination of sight, vestibular systems (inner ear mechanism), and proprioception which is the awareness of one’s place in a 3 dimensional space.
The primary mechanism used for functional balancing is the movement of the fluid known as endolymph - can also be referred to as Scarpa’s fluid after the 18th century Italian anatomist Antonio Scarpa - in the inner coils of 3 separate semicircular canals, of which are housed in what is called the bony labyrinth. The anterior (superior) and posterior canals are of right angles to each other and are placed at 45 degree angles in relation to the frontal and sagittal planes of the body. The frontal plane parallel to your face, and the sagittal plane cuts your body in half from your nose to your groin. Then the horizontal (lateral) canal is about 30 degrees from the horizontal plane (30 degrees off parallel from the ground).
These 3 canals act to control the head’s pitch, yaw and rotation in the xyz planes (which is the 3 dimensional plane we use). When the head moves in any of these directions, the fluid moves out of place and pushes on hair cells contained at the ends of the canals that translate their movement to signals to the brain. When you spin around too fast and for too long, the liquids continue to move around once you’ve stopped; this is what causes you to lose your balance after spinning. This movement of the liquid inside your inner ear canals after your body has stopped moving is caused by inertia.
The same property can be used to tell if an egg is raw or hard boiled. First, spin the egg, then quickly grasp it with you hand and then let go again. If the egg just stops, then the egg is hard boiled. If after you let go then egg starts spinning again, then the egg
The human’s reliance on this vestibular system for balance is quite clear, so when damage and disease catches on, it is a great cause of vertigo (inaccurate perception of motion, similar to stopping after spinning in your office chair for too long) for the organism. There are peripheral (vestibular system/inner ear caused) and central vertigo (brain or the back of the brain called the cerebellum). Peripheral vertigo can include stopping after spinning for too long, or with diseases such as the Meniere’s disease which causes an inner ear fluid disorder that can cause long episodes of vertigo and hearing loss.
A common case of central vertigo for anyone who’s been a child riding in a car before has probably experienced (myself a lot) is motion sickness, which is generally but not exclusively caused by a disagreement between the visually perceived movement and the movement felt by the vestibular system. This can apply to almost any vehicle, from sea sickness, car sickness or air sickness, they are all forms of this motion sickness connected to central vertigo. This confusion between visual and vestibular motion can also be simulated with centrifuge machines like the UFOs or amusement park rides that close you off from the outside world. Astronauts also train in these machines that try to induce motion sickness by cutting off your visual perception of motion.
The importance of balance and the vestibular system should be clear now, and it is surely not a sense that you should ever take for granted. They are one of the most important tools for your survival as they allow movement to keep you balanced while running and moving. As you age, some of these balancing systems - among others as well - and prove to be a real threat of injury to the older population especially. Fall relating incidents are the leading cause of death among the older adult population (over 65 years of age). So don’t take your sixth sense of balance for granted, and also be proud of your extra sense.