Sight, Taste, Hearing, Touch, Smell. Those 5 things are significant. They are the traditional senses. Put “Sense of …” in front of any single one of them and it makes sense, if you’ll pardon the pun. This view was proposed first by Aristotle, a great Greek philosopher of some note. However great he may be though this is very untrue. We have 5 senses yes, but we also happen to have at least 4 more, depending on what you think constitutes a sense. Most experts in the field think we have at least 21.
What is a sense though? – A system with specialised cells which respond to a specific physical phenomenon and correspond to specific regions of the brain where they are received and interpreted. So with that out-of-the-way, what are the other senses?
Thermoception – Sense of heat. Feel cold? That’s thanks to thermoception. This sense depends upon specialised nerves in the skin. It also links into the sense of pain, which is useful, unless you happen to want to boil or freeze parts of your body.
Kinesthetic Sense – Knowing how big your limbs are and their position. Close your eyes and touch your nose with one finger. Success? I’ll assume so – that little victory just now was thanks to this handy sense. Without it you wouldn’t be able to do anything in the dark. In fact you probably wouldn’t be able to tell if your arms were still attached. So yes. This is a useful one.
Pain – Also known as Nociception. There are three types of pain, somatic, cutaneous and visceral. These apply to organs, skin and bones respectively. This sense may be a real pain (sorry) but it is really quite useful. Without it you would cut yourself and bleed without knowing. It’s pretty vital.
Vestibular Sense – Simply a sense of balance. This is detected by the vestibular system in your inner ear. Thanks to this you can do stuff like walking.
Needing the Bathroom – When your bladder reaches 25% volume a signal is released from the Detrusor muscle which is a layer of the bladder. This signal makes you want to, empty your bowels. As the bladder fills up further past the 25% mark the urge becomes harder to ignore and when volume reaches 100% you… no longer have a choice in the matter. Thanks goodness for this sense. Can you imagine what life would be like without it? (There is also an equivalent for your bowels, also useful).
Itching – This one helps us tell when light insects are crawling over us. It was so important to our ancestors that we actually have a complete second set of special nerves just for detecting itching.
And so we close with itching, but we have only just scratched the surface of the world of senses. Beyond the obvious ones Aristotle noted, and the obvious ones he missed there are the internal ones. For example the sense of really needing that bathroom – that’s a prominent internal sense. A less prominent one is your sense of the pH of the fluid around your spinal cord.
There are at least 10 more. Additionally a sense of time, which is very accurate in adults but we still have no idea how people do it. There is a lot more to the human body than there seems at first. Keep that in mind.
(Also there are bucket loads of senses that other animals have which we don’t; such as the ability to detect the strength and direction of magnetic fields. )