Humans Have a Lot More Than Five Senses

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Today I found out humans have a lot more than five senses.  It turns out, there are at least nine senses and most researchers think there are more like twenty-one or so.
Just for reference, the commonly held definition of a “sense” is “any system that consists of a group of sensory cell types that respond to a specific physical phenomenon and that corresponds to a particular group of regions within the brain where the signals are received and interpreted.

The commonly held human senses are as follows:

  • Sight:  This technically is two senses given the two distinct types of receptors present, one for color (cones) and one for brightness (rods).
  • Taste:  This is sometimes argued to be five senses by itself due to the differing types of taste receptors (sweet, salty, sour, bitter, and umami), but generally is just referred to as one sense.  For those who don’t know, umami receptors detect the amino acid glutamate, which is a taste generally found in meat and some artificial flavoring.  The taste sense, unlike sight, is a sense based off of a chemical reaction
  • Touch:  This has been found to be distinct from pressure, temperature, pain, and even itch sensors.
  • Pressure: Obvious sense is obvious. ;-)
  • Itch:  Surprisingly, this is a distinct sensor system from other touch-related senses.
  • Thermoception:  Ability to sense heat and cold.  This also is thought of as more than one sense.  This is not just because of the two hot/cold receptors, but also because there is a completely different type of thermoceptor, in terms of the mechanism for detection, in the brain.  These thermoceptors in the brain are used for monitoring internal body temperature. Continue reading
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