From the childhood itself we are taught that human beings have five senses: sight, hearing, speech, smell and touch. However, according to the latest research, the classification is not so simple. The progress in neuroscience has paved way for some radical changes in the traditional concepts. Different persons have given different definitions to the word sense, though it is basically regarded as the way which we receive information. While the five senses give us an understanding of our surroundings, there are still many things our brain detect which are overlooked by us. And the five senses cannot explain those.
The idea of five senses is a very old one, some tracing it back to the book On the Soul, written by Aristotle, in which he dedicates a chapter to them. However, our senses are facilitated by the activities of brain and the vast network of neurons. For example, the sense of touch is a combination of different senses like heat, cold and pain, each sensed by different groups of sensors.
The modern science has concluded that our senses number around 21 rather than five. The big five senses themselves are combinations of different sensors as seen in the example of touch. Consider the sense of vision; it is actually a combination of two receptors. There are Rods, which sense the light intensity and the Cones which help to identify the colors.
|The Human Senses (click to enlarge)|
There are two sound sensors in our ears, and also those which give us the sense of balance. In our skin, there are receptors sensitive to heat, cold, pressure, pain and itch. Also various sensors on tongue provide the sense of taste. The chemical sensors in nose give the sense of smell and they together with taste sensors produce flavors.
There are various other senses which are less obvious to us. There is a sense called proprioception which makes us aware of the location of our body parts. It’s because of this sense we can touch our body parts with eyes closed.
There are other various sensors which give us the information about inner body workings. The senses of hunger and thirst are examples of this. So are the senses that indicate when it is time to urinate or defecate. There are a lot of other senses, like chemoreceptors which detect blood-born hormones, magnetoreceptors which detect magnetic fields. The scientists have also determined that the humans have an accurate sense of time. The parts those responsible for the latter are cerebral cortex, cerebellum, and basal ganglia. It will vary depending on how we look at it, but the senses are way more than five.
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