138. Why 5 Doesn’t Make Sense

07 Jun

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. )


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7 responses to “138. Why 5 Doesn’t Make Sense

  1. Anonymous

    June 24, 2012 at 10:57

    Put your hand in cold water then put it in luke warm water. It feels hot. You’re not sensing temperature but the rate and direction of heat being transferred from or into your hand.

  2. Anonymous

    August 11, 2011 at 17:08

    Hi i read somewhere the saddest movie in the world, The Champ (1979) directed by Franco Zeffirelli. It was used by psychologist to induce sadness.

    • Anonymous

      May 17, 2015 at 11:42


  3. Anonymous

    August 9, 2011 at 10:35

    Did u know that the gated pathway for pain or nociception is also the same pathway for tickling?

  4. Gash

    June 9, 2011 at 15:14

    What about spider-senses?

  5. Frater Bovious

    June 9, 2011 at 14:49

    On the other, other hand, aren’t all these senses just specialized senses of touch? Certain molecules touch receptors in the nose and we smell. Ditto for taste. Inner ear parts respond to being touched by moving air and we hear. Photons touch our optic parts and we see. Etc. In that context, if we isolate all the different ways we feel, then 21 senses is very conceivable.This could maybe even be extended to “feelings” like sadness, etc.

    • Alexandre R.D.M. Coates

      June 9, 2011 at 18:24

      Very astute of you, I agree almost completely. All of our overt and obvious senses are based upon contact, then exactly as out even the contact of electromagnetic waves such as with sight.

      However there is one counterpoint, but it is also the mystery really. Sense of time. No cells can be found which are specialised for time measurement and detection and as far as I know we are not constantly hit by waves or particles of time from which we can infer information. However this sense is still incredibly accurate in many humans. This is the only sense I can consider completely exempt from the abstraction ‘all senses are a form of touch.’ Technically it is not a sense because we can find neither a mechanism nor any specialised cells which correspond to it, but we undeniably feel it as a sense, coming to use it and rely upon it.


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