With the help of analyzers of various types, a person is guided in the surrounding world. It is through vision, hearing, smell and other senses that we sense the external environment and recognize the dangers. For each person, different analyzers may not be developed equally. We will try to figure out in the article what the olfactory analyzer is. The structure and functions, the importance for the health of one of the senses are discussed in this article.
Definition of the sense of smell
A person perceives most of the information about the world around him with the help of his organ of vision, but without a sense of smell the picture would not be so vivid and understandable.
The olfactory system is designed to recognize substances that are soluble and volatile. This system creates subjective images in the form of certain odors. The value of the olfactory analyzer also lies in the fact that it is able to provide an objective assessment of the quality of air, food and the environment as a whole.
If we compare the organ of smell in humans and animals, then we can say that for animals this organ is of particular importance. But it may not be developed equally for everyone. For example, there are life forms in which the olfactory analyzer is well developed. So, some species of butterflies can find their partner by smell at a distance of up to 8 kilometers. Everyone knows dogs that can follow the trail of a person, guided by the smell of his things.
The functions of the sense of smell
If we consider the functions of the olfactory analyzer, we can note the most important and significant:
- Analysis of food for edibility and attractiveness. Using this system, you can determine the degree of suitability of the product.
- The formation of eating behavior.
- The olfactory analyzer is directly involved in setting up the digestive system for food processing.
- Determination of substances hazardous to the human body.
- The formation of sexual behavior, which can change under the influence of pheromones.
- With the participation of this analyzer, a person is oriented in the environment.
- Cognition of the outside world is not complete without an organ of smell.
It can be noted that in people who are blind, their sense of smell can be exacerbated, and they smell much better, which helps them navigate this world.
Olfactory analyzer structure
If we consider the structure of this sensory organ, we can note the following departments:
- Peripheral. It includes receptor cells located in the nasal mucosa. They end with cilia surrounded by mucus. In it, odorous substances dissolve. There is a chemical interaction, which is converted into a nerve impulse.
- The conduction section consists of the olfactory nerve. According to it, signals from receptors go to the forebrain, where the olfactory bulb is located. In it, the primary analysis of information occurs, then the pulses will go to the next section of the analyzer.
- The central section is located in the temporal and frontal lobe of the cerebral cortex. It is here that the final research of information is carried out, the smell is recognized, and the final response of our body to its effect is formed.
We will get acquainted with the structure and functioning of these departments in more detail.
Peripheral part of the analyzer
Considering the structure of the olfactory analyzer, it is necessary to begin with the initial section. It is located in the nasal cavity. In these places, the mucous membrane is slightly thickened, covered with mucous secretions on top, which play a protective role, protect against drying out, and also participate in the removal of the remaining irritants after the end of their exposure.
It is here that contact is made between odorous substances and receptor cells. Two types of cells are distinguished in the epithelium:
- Supporting. They take part in metabolic processes.
- Olfactory. These are the receptors themselves, which have a large number of cilia to increase the area of contact.
The olfactory cells have two processes, one of which extends to the olfactory bulbs, and the second has the shape of a stick and ends with a bubble with cilia.
Conductor department
This department is designed to carry out information, therefore it is represented by the nerve pathways that form the olfactory nerve. It consists of individual bundles going into the visual tubercle.
There is a connection with the limbic system, which explains the presence of emotions in the process of perceiving odors. For example, some smells can cause pleasure, others - disgust, and so on.
Analyzer Central
This department includes the olfactory bulb. This also includes the department in the temporal lobes of the brain.
All this is located in front of the pear-shaped lobe of the cortex in the hippocampus.
Odor mechanism
To effectively absorb irritating substances, their molecules must first dissolve in the mucus that surrounds the receptor cells. Then there is an interaction with special proteins embedded in the cell membrane.
Such contact is possible if the shape of the stimulus molecule matches the shape of the protein. The mucous substance controls the surface availability of the receptors for odorous molecules.
After the stimulus molecule has come into contact with the receptor protein, the structure of the latter changes, as a result of which the sodium ion channels in the membrane open. Sodium ions penetrate inside and create positive charges that lead to membrane depolarization.
A mediator is released from the receptor cell, which leads to the appearance of a nerve impulse in the departments of the nerve fiber. Thus, in the form of nerve impulses, olfactory excitation begins to be transmitted to other parts of the analyzer.
The functioning of the olfactory system
If you imagine how the olfactory analyzer of a person works, then all the work can be divided into several stages:
- Advancing an odorous stimulus to receptor cells, which ends with a connection with receptor proteins.
- Converting the chemical effects of odorous substances into nerve impulses. This stage begins with the attachment of the stimulus to the receptor and ends with the generation of nerve impulses.
- The movement of a nerve impulse to the lower nerve center. It can be deciphered as a movement towards the olfactory bulb.
- Impulse conversion in the olfactory bulb.
- Advancement of nerve impulses to higher olfactory centers.
- Building an image of irritation in the form of a specific smell.
All these steps follow one after another. If problems or abnormalities are observed on one of them, we can say that the perception of odors is impaired.
Addictive olfactory analyzer
We analyzed the features of the olfactory human analyzer, but it is also worth noting that this sensory system is able to adapt. This happens with prolonged exposure to the stimulus.
The adaptation of the analyzer can take place within a few seconds, and sometimes it takes up to five minutes. It all depends on a number of factors:
- Duration of contact with odorous substance.
- The concentration of the stimulus.
- Air velocity.
There is a fairly large group of odorous substances, to which the olfactory analyzer adapts quickly. Very little time passes, and the smell ceases to be felt. A vivid example is the complete adaptation to the smell of your body, room, and things.
For some irritants, addiction is formed slowly or only partially in general. When exposed to a weak olfactory stimulus for a short time, addiction can manifest itself in the form of an increase in the sensitivity of this analyzer.
It has already been established that the development of adaptation does not occur in the first section of the analyzer, but in the last, that is, cortical. Often, when the same odorous substance is exposed for a long time, a persistent focus of excitation is formed in the cerebral cortex. In these situations, a sense of smell can occur when exposed to other irritants. Sometimes this feeling can become annoying and appears even in the absence of irritants. In this case, we can talk about hallucinations, or illusions.
We can only say with confidence that if adaptation to one particular smell is observed, then this will not affect the perception of other stimuli, since all stimuli act on different receptors.
Theory of Perception of Odor
Currently, more than 10 thousand odorous substances are known. All of them can be grouped into seven classes of primary odors:
- Floral.
- Mint.
- Musky.
- Ethereal.
- Putrefactive.
- Camphor.
- Caustic.
If there is a mixture of several odors, then its olfactory analyzer can be perceived as a completely new aroma. Molecules of various substances differ in different shapes, for example, the camphor odor has round molecules, and the musky odor in the form of a disk. In addition, they also differ in electric charge: some may have a positive, while others may have a negative.
There are many theories that try to explain the mechanism of perception of odors. Currently, the most common is stereochemical, which claims that there are several types of sites on the membrane of receptor cells. They are distinguished by their structure and electrophilicity. They are able to recognize odorous molecules of a certain shape and size.
Varieties of sense of smell
In addition, the olfactory analyzer is not equally developed in all, and in addition, some violations and deviations in its work can be observed:
- Anosmia is a complete lack of ability to perceive odors.
- Hyposmia is a decrease in smell.
- Hyperosmia, on the contrary, is observed with increased olfactory sensitivity.
- Parosmia characterizes inadequate perception of odors.
- Disturbance of differentiation.
- The appearance of olfactory hallucinations.
- Olfactory agnosia is given if a person smells, but cannot recognize.
It should be noted that with age there is a gradual decrease in olfactory sensitivity. The olfactory analyzer is no longer able to recognize odors so clearly and quickly. Scientists estimate that by the age of 50, the average person’s sense of smell is halved compared to youth.
Olfactory analyzer and its age features
The very first during the intrauterine development of the olfactory analyzer, the peripheral section begins to form. This happens already at 8 weeks of development. By the end of pregnancy, or rather, by the end of 8 months, this analyzer is already fully formed.
Right after birth, you can observe the reaction of the newborn to smells. This is manifested in the form of facial movements, changes in the work of the heart muscle, respiratory rate, and body position.
It is with the help of smell that the baby learns the smell of his mother. This sense organ is an important component in the formation of food reflexes. Gradually, as a child grows up, the analyzer’s ability to differentiate odors increases. The fineness and strength of this process increases by 4 months.
If we compare the ability to perceive and differentiate odors in children 5-6 years old and in adults, then we can say that in the latter it is much higher.
These are the age-related characteristics of the olfactory analyzer. We can also say that as a result of systematic training, you can significantly improve your sense of smell, but heavy smokers run the risk of losing perception, since the components of tobacco smoke adversely affect receptors. Frequent inflammatory diseases of the nasal cavity also contribute to a decrease in smell.
So we examined the olfactory analyzer. Its structure and functions are described with all possible accessibility. It is safe to say that all the senses are important to humans. If there are problems in the operation of at least one analyzer, then we can already say that the adequacy of the perception of the surrounding world is reduced, the fullness of sensations from life disappears. Take care of yourself and your senses.