We explain what the sense of smell is, what it is for, how it works and how to take care of it. Also, what are olfactory receptors.
What is smell?
Smell or sense of smell is called one of the five senses with which humans and many animals can perceive the surrounding reality. In this case, it is the ability to detect particles and traces of chemicals in the air, using receptors in the nasal cavity (that is, the nose).
Smell is a very common ability in nature, so much so that it is the primary sense of many animal species. However, in the case of invertebrates and amphibians it is more diffuse and less recognizable, since these animals have the ability to perceive chemicals from the environment through the skin and other organs very different from the nose of higher vertebrates.
In any case, through smell we perceive smells: particles that are detached from matter and remain in the air, from where they are taken up during respiration by specialized nerve receptors in the nose.
In the case of human beings, it is a little cultivated sense, in relation to sight and hearing, but no less important, since it connects much more quickly with our memory. It is estimated that we can recognize around 10,000 different smells on average throughout our lives, distinguishing between pleasant and unpleasant, pleasant and stimulating.
What is smell for?
The sense of smell is critically important to living things, since allows to recognize matter without coming into direct contact with it, and even having no idea that it is there.
Being a passive sense, requiring little concentration, is a continuous source of information with respect to the environment, revealing the presence of smoke or strange odors that can alert you to a threat. In addition, smell allows us to identify familiar environments (which is precisely why animals “mark” with their smell) and to warn of the state and composition of the food before ingesting it.
How does smell work?
The sense of smell is the interaction between odoriferous molecules (that is, with odor) present in the atmosphere and specialized receivers present in the nasal mucosa, neurons capable of transforming chemical information into electrical impulses that are transmitted to the brain.
For this to happen, the air loaded with odoriferous particles must be inspired, and come into contact with the olfactory mucosa that lines the inside of the nose. There, the olfactory sensory cells (around 20 or 30 million on average) pick up these chemical traces and transport them through their cilia (filaments) and fixing proteins present in the mucus, so that they can meet the specialized neuroreceptors.
The nerve information from these neurons penetrates the skull through microholes in the cribriform plate of the ethmoid bone, and in the anterior region of the brain, they reach the olfactory or olfactory bulb, a neural structure of the forebrain that recognizes information and transmits it to the upper areas of the brain, where it enters conscious thought.
Smell is a sense very similar to taste, since both consist of chemoreception, but while the first is at a distance, the second is through direct contact with matter. Both stimuli, in fact, are processed in the taste center and the taste in the middle part of the frontal lobe, that is, in the same region of the brain.
Olfactory receptors
Olfactory receptors They are in charge of converting the chemical information of the smell into nervous information. They are found in the mucosa of the nasal cavity, distributed in two clearly differentiated regions:
- The red pituitary, with a large presence of blood vessels but without olfactory functions, which heats the inhaled air and filters it of impurities and particles.
- The yellow pituitary, where the olfactory cells that contain the smell receptors are found.
Smell receptors are many and highly specialized, especially in mammals. It is thought that there may be up to 1000 different receptors, so the proteins responsible for processing odor occupy a good portion of the genome.
Each of the specialized receptors recognizes a different type of odorTherefore, the so-called “primary odors” (which make up other more complex aromas) are very many and difficult to define.
Even so, it is estimated that the odors available to humans can be classified into 10 different lines: fragrant or floral, woody or resinous, chemical, citrus, non-citrus fruit, menthol, sweet, smoky or burnt, rotten and pungent or rancid.
Smell care
Taking care of the olfactory sense is reduced to taking care of the nose itself and its internal components. For this, it is advisable to comply with the following recommendations:
- Keeping the nostrils regularly clean, by blowing but without pressing the nose excessively.
- Do not put objects into the nasal cavity, much less those that can hurt it, change its chemical constitution or that can lodge inside.
- Avoid cigarette smoking and similar substances, as well as highly odorous aerosols.
- Do not expose yourself to high concentrations of humidity, dust or substances with strong odor for a long time.