“You have a sixth sense” it is said attributing someone else a sort of super-power, which goes beyond the canonical five senses. Yet the known senses are well over five. To be exact, there are 9, not to mention the secondary senses, which would bring the list down to 21, depending on how you define a sense. Perhaps the simplest definition is: a sense is a channel through which your body can observe itself or the outside world.
You’re familiar with the big five: vision, hearing, smell, touch, and taste. But have you ever heard of proprioception? If you close your eyes and lift a finger to your nose, you know exactly where it is, without seeing it.
Then you should add balance, thermoreception and pain.
To us it seems appropriate to add the sense of time.
Here is the complete list:
1, Sight. Wanting to be punctilious, this sense could be divided into two, since there are two distinct types of receptors, the cones and rods, which perceive the color and movement.
2. Taste. Again, someone believes it should be divided into five (maybe six) based on the type of perceived taste, but it would probably be a distinction of pure fussiness. We said five flavors, because the perceived flavors are not only sweet, salty, bitter, sour, but there is also umami, that is, the taste of glutamate (present in protein-rich foods such as meat and cheese). In addition, recent studies point out that there would be a sixth taste, with specialized taste buds for fat.
3. Hearing. The ability to perceive vibrations in the air or in any case in the gas / liquid in which it is immersed.
4. Smell. The ability to smell. Flavors are generated by the combination of taste and smell.
Humans may be able to smell over 1 trillion scents, according to researchers. They do this with the olfactory cleft, which is found on the roof of the nasal cavity, next to the “smelling” part of the brain, the olfactory bulb and fossa. Nerve endings in the olfactory cleft transmit smells to the brain, according to the American Rhinologic Society.
5. Touch, it is the human sense that allows living users to detect the presence of stimuli, through the contact of the epidermis with external objects. Tactile sensitivity affects a large body surface: there are about 130 tactile receptors for every square centimeter of skin.
6. Theroperception. It is the ability to perceive the cold and the heat. Again, someone believes that two distinct senses should be considered, due to the diversity of receptors and relaxation mechanisms.
7. Proprioception (or kinaesthesia). It is the ability to perceive the position of one’s body and individual limbs in space. For the record, it is one of the senses that is altered by alcohol consumption, and it is the one that is tested with the well-known “close your eyes and touch your nose” method.
8. Pain. Once it was believed that pain was an “overload” of other senses, such as touch, but in reality pain has receptors and a sensory network of its own. Indeed, there are actually three distinct ones: the cutaneous one on the skin, the somatic one on the bones and joints, and the one relating to the internal organs.
9. Balance, Allows you to perceive accelerations (including gravity). The organ of balance is the vestibular labyrinth, which is located in the inner ear.
10. Time. It is not clear how the perception of time works, but it is a fact that humans have a very precise perception of time, especially when young.
The following ones, on the other hand, can be traced back to others quite directly and therefore as secondary they should not be added to the list.
11. Pressure. Commonly called “touch”, it is the ability to sense pressure on a specific area of the body.
12. Itching. As surprising as it may be, itching has its own sensory system, distinct from that of touch.
13. Tension. It allows the brain to control the state of tension and the contraction of the muscles.
14. Stretching. Specific receptors for stretching are found in particular in the lungs, bladder, stomach and intestines. Often this sense would also be related to headaches, in particular related to the perception of dilation of blood vessels.
It is instead difficult to establish whether these should be considered senses. But if they are not senses, what are they? Don’t you say I feel hungry, thirsty?
15. Chemo perception. It is the perception of chemical stimuli, in particular held by hormones.
16. Thirst. Thirst is an autonomous sense, which is activated when hydration of the body lowers
17. Hunger. Even hunger has its own autonomy as a sensory network.
18. Magnetism. The ability to detect magnetic fields. Bats use this to navigate. Stranger still, there are certain bird and insect species that sense and steer their flight by polarized light.