Scientific Sundays #2: Do Humans Have Five Senses?

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Sorry for not posting an article last Sunday, we had some ‘business’ to do. To cover, we’re posting two!

All of us know that there are 5 senses, right? Wrong. This is one of the big fat lies that your science teachers have told you. In fact, most research shows there are plenty more; we actually have up to around 20 senses. It’s just that these senses are filtered into the main five (sight, touch, taste, sound and smell), but they are actually quite different from each other.

What are the five senses?

First of all, we have sight, which in itself has two sub categories, one for colour and one for brightness. These are cones and rods respectively. Cones are used mainly in the day, with rods, as otherwise we would not see colour and it would be like living in a 1920s Charlie Chaplin picture. However, in the darkness, rods take over to take in as much light as possible so you can see a little.

Secondly, we have taste, which by itself has five sub senses, which is why we can taste sweet, sour, bitter, salty or umami (umami tastes an amino acid found in flavourings). Each sense of taste is a different chemical reaction taking place, but are regarded as one sense, and is debatable.

Touch, one of the most regularly used senses, is significantly different from other things we regard as touching. For example, pressure, this explains itself. Itching, which detects potential bodily harm which is why you itch when you touch stinging nettles (they are acidic, skin is alkali). Temperature, which arguably is two senses (hot and cold receptors), as your brain deals with each separately. Pain was thought to be a sensory overload, but we now know it can’t be as we feel pain inside us (when you get winded, muscle and bone ache, and on the skin e.g. a pinch).

Sound does not have any more branches, our ear drums detect each according to vibrations on separate areas of the ‘drums’. Smell is linked to taste, as we all know and works in the same way too, through chemical reactions. In addition to taste, allow for flavours to be recognised.

In addition to these, there are some other senses that don’t really fall into one of the main five categories we have, or fall into more than one. Proprioception is the sense that tells you where your body parts in relation to each other which is why you can close your eyes and be able to touch each part of you with high accuracy. This is almost like a system in your body that links everything together. We then have thirst, which you could say is taste, but is a monitor of the amount of water in your body, and your body detects when you are dehydrated, making you thirsty. Hunger is the same as thirst, but with food and nutrients.

Time is a very peculiar sense, if we can call it so. We have no system that allows us to detect lengths of time, yet we have found that we can sense how long a period of time is. This apparently has something to do with a ‘rhythm’ in our bodies. The other senses you might want to find out about are: Magentoception (direction), stretch and tension (in muscles and organs), equilibrioception (balance) and chemoreception (unnatural substances, involved in vomiting).

We have not covered everything, but hope we have got you interested to find out more. Did you know all this before? What interests you? Let us know in the comments, and spread the word!

SS

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Posted on October 21, 2012, in Scientific Sundays and tagged , , , , , , , . Bookmark the permalink. 2 Comments.

  1. Interesting and fascinating.

  2. Very interesting, but debatable. Yes we have been taught about 5 senses and the reason mainly is to generalize a theory to mainly understand the basics just like solar system.

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