How Many Senses Do We Really Have? You Might Not Know About These 3 — VIDEO
You've almost certainly been told, since a young age, that you have five senses with which to explore the world. But hold onto your hats, because the real truth is that humans have extra senses. These bonus senses — there are three of them, and maybe more to be discovered — are a little less straightforward, but super critical to navigating life as we know it.
To take things back a step, maybe your memory is a little rusty even on the basic five senses. As a refresher, they are touch, taste, smell, hearing, and vision, of course. Each of these senses is very easy to understand, and easy to visually represent to children via their respective body parts (hands, mouth, nose, ears, eyes).
The three extra senses are harder to explain and harder to represent pictorially than the basic ones, which is probably why teaching only five senses to children makes sense at the time. But we're all grown now, and it's time to learn the rest of the story. There may be even more additional senses to come, so you'd better catch up before your knowledge becomes even more obsolete. This helpful video from SciShow, via Hello Giggles, is a good place to start in beginning to learn about the three extra senses.
As you may have guessed from its root "thermo," thermoception is the ability to detect temperatures. Apparently, every organism with a nervous system has thermoceptors, so this sensory modality is nowhere near distinctly human. It may seem like thermoception should be included in the regular old sense "touch," but it would definitely be possible to have a sense of touch (allowing you to detect differences like smooth vs. bumpy) without having any ability to detect the hotness or coldness of the surface, so they're separate.
Thermoception is made possibly by special thermoceptor neurons in the brain, which are turned on and off by different temperature ranges to encourage the creature to respond appropriately (such as by moving towards warmth and away from cool, or vice versa, depending). Even fruit flies have them!
Proprioception is basically the ability to control your body parts effectively in space without looking at them. This is hugely useful because then your vision is freed to do other things, like fine tuning of various sorts. Without proprioception, you wouldn't really be able to throw a ball, use a sewing machine, or stick your feet into the pedals of your bike. Unlike thermoception, though, there are no special parts of your body working just to provide proprioception. Instead, it's a function of lots of bits of info coming from different muscles and joints and arriving in your brain at once. This provides a coherent picture of what your body's doing at the moment, and where.
Again, this sense seems sort of related to the sense of touch, but it's not quite the same. You could have the ability to feel things on your skin without having any clue at all where your limbs are in space. Perhaps the clumsier among us are a little deficient in proprioception.
This sense allows you to balance. Without equilibrioception, an animal would fall constantly and probably get hurt. In addition to the brain, the inner ear plays a big role in balancing. Some of the tiny bits in there contain fluid that moves around when you do, thus providing info about your body's orientation as compared to the ground.
Equilibrioception is sort of a delicate capacity, and injuries or disorders of the inner ear can easily cause you to lose your sense of balance. Humans aren't the absolute best at equilibriocepting, though. Cats, for instance, have tails that provide even more feedback about balance and the ability to correct it.