Thursday, February 18, 2010

Science Byte

Today's Science Byte is brought to you by Guyton & Hall's Textbook of Medical Physiology, p. 572.

Have you ever wondered about your 5 senses & how your body goes about actually sensing? Sure, your eyes see & your ears hear - but how? When you get down to the cellular level, specialized cells in these organs & throughout the body have special sensing receptors* that detect changes in our environment & convey these to our brain for processing.

There are 5 types of these sensing receptors but they don't correspond exactly to our 5 senses. They are as follows:
  1. mechanoreceptors: detect stretching or compression of the surrounding tissues - includes sounds receptors of the inner ear which detect the vibrations transmitted by the ear drum
  2. thermoreceptors: detect changes in temperature - some being cold, some hot
  3. nociceptors (AKA pain receptors): detect physical or chemical damage
  4. electromagnetic receptors: detect light on the retina of the eye - rods & cones for detecting white & coloured light, respectively
  5. chemoreceptors: detect various chemicals - includes taste & scent detection, blood oxygen, carbon dioxide & glucose levels
So as you can see, there is more to it than just the 5 senses. But if you do break it down by the 5 senses, then you get:
  1. touch: mechanoreceptors, thermoreceptors & nociceptors
  2. taste: chemoreceptors (& nociceptors - spicy foods act on pain receptors to give you that burning feeling)
  3. sight: electromagnetic receptors
  4. smell: chemoreceptors
  5. hearing: mechanoreceptors
The only problem with this outlook is that you forget that the chemoreceptors have many more functions than simply allowing us to enjoy tastes & smells (or not).

*receptor: a receptor is basically a large protein on a cell that has at least one pocket or binding site where some chemical or compound can attach. Receptors are often on the membrane of the cell so that it can detect changes in the environment surrounding the cell. Receptors can also be found inside cells where they detect any chemicals that may have made their way into the cell.

Have a request for the next Science Byte? Feel free to leave a comment with your favourite science topic or any burning questions you may have!

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