Taste analyzer: structure and functions

Information coming from the outside world is perceived by our senses. Thanks to their selective work, the human body is able to respond adequately to all changes in the environment. The end result of the functioning of sense organs, namely hearing, sight, smell, taste, tactile sensitivity and vestibular apparatus is the emergence of sensations and the recognition of stimuli.

The great Russian physiologist IP Pavlov established that cortical centers of the brain participate in the formation of sensations, the excitation coming from the receptors of the nerve endings through the centripetal nerves. Systems, consisting of sections of the cerebral cortex and conducting pathways - nerves and receptors, he called analyzers, or sensory systems. A taste analyzer whose structure and functions are defined by its anatomical and morphological features will be studied in this article.

The mechanism of the appearance of taste sensations

Virtually all substances used by us as food have a taste. In physics, there are 4 main tastes: sweet, bitter, acidic and salty, the perception and differentiation of which is carried out by the taste analyzer. Taste can be explained as the perception of molecules of chemicals that make up food, receptors located in the mouth and in the tongue. To understand what function the taste analyzer performs, let us turn to the study of its structure. So, let's look at how this area of our body looks.

The departments of the taste analyzer

In our body there are special systems that are responsible for hearing, sight, smell, tactile feelings. The taste analyzer, the structure and functions of which we study, consists of three parts. The first is called peripheral, or receptor. It directly perceives environmental stimuli, which cause weak currents in the nerve endings that transform into bioelectric impulses.

They are transferred to the second section of the taste analyzer - conductor. It is represented by an afferent nerve. According to this, excitation enters the cortical part of the taste analyzer, which is a specific part of the brain, in which the formation of taste sensations occurs.

Features of the periphery

The taste analyzer, as it was said before, consists of three parts. Consider in more detail the receptor, or peripheral department. It is represented by chemoreceptors that perceive stimuli in the form of various chemical compounds, and recognizes them by force, quality (modality) and intensity. Hemoretseptory are part of the taste buds, or bulbs, which dot the mouth and tongue. Nerve endings that are sensitive to salty taste are on the tip of the tongue and along its edges, to bitter - at the root of the tongue, to the sweet - at the tip, to the sour - at the edges.

The taste bud itself does not go directly to the surface of the mucous membrane of the tongue, but has a connection with it through the taste period. Each chemoreceptor contains from 40 to 50 villi. Substances that make up the food contact and irritate them, so that in the peripheral part of the taste sensory system there is a process of irritation, which turns into excitation. With age, in humans, the threshold of taste sensitivity increases, that is, the ability to recognize a variety of flavors is extinguished.

In animals, the sensitivity of the taste analyzer practically does not change with age, moreover, the relationship between the taste and olfactory systems is much more pronounced in them. For example, in cats, taste receptors (Jacobson tubes) are also also olfactory nerve endings, which contributes to a more subtle discrimination in the quality of food.

How does the conductor part work?

Continuing to study the sections of the taste analyzer, we will consider how the nerve impulses from chemoreceptors can reach the brain. To do this, there is a conductor part. It is represented by fibers of a single path. It includes several nerves: facial, lingopharyngeal, wandering and lingual. It is through them that the nerve impulses enter the stem part of the brain-the medulla oblongata and the bridge, and from them to the visual thalamus and finally to the temporal lobe of the cerebral cortex.

Damage to the conductor part of the taste analyzer, for example, as a result of the paresis of the facial nerve leads to a partial loss of taste sensitivity. Surgical interventions, for example, in operations on the facial part of the skull, reduce the conductivity of nerve impulses along the nerves of a single path, especially the wandering and facial ones, which also leads to a decrease in taste sensitivity.

Cortical part of the taste sensory system

The cortical part of any of the existing analyzers is necessarily represented by the corresponding portion of the central nervous system located in the cerebral cortex. It performs the main functions of the taste analyzer - perception and difference of taste sensations. Excitation through the centripetal nerves enters the temporal lobe of the cerebral cortex, where the final differentiation of the salty, bitter, sweet and sour taste of food takes place.

Interrelation of the structure and functions of the taste analyzer

All three sections of the taste sensory system are inextricably linked. Damage to any of these parts (receptor, conductor or cortical) or their connections leads to a loss of the ability to perceive and discriminate between taste sensations. The anatomical structure of the taste analyzer determines the specificity of the taste sensations that result from the stimulation of the chemoreceptors of the taste buds.

Appetite. How does it arise?

The emotional-physiological need for food intake and the positive sensations that arise before its consumption and in the process of eating are usually called appetite. In its formation, in addition to the organ of vision, taste and olfactory analyzers are involved .

The smell, the type of food and, of course, its taste are the conditioned stimuli that cause the excitation process in the nerve endings of the taste buds. It enters the center of digestion, located in the medulla oblongata, as well as in the structures of the limbic system and the thalamus.

The mechanism of recognition of taste sensations

As was established by physiologists, excitation in chemoreceptors of the tongue arises as a result of food, olfactory and visual stimuli (taste, appearance and smell of food). Recognition of various types of taste (bitter, sweet, sour, salty) and their shades is due to the analytical and synthetic activity of the upper brain region - the cortex of the cerebral hemispheres. In its temporal lobe there is also a taste center.

The various pathologies and injuries to which the taste analyzer is exposed lead to agesia - a partial or total loss of taste sensations. It can also occur in a healthy person as a result of viral diseases of the upper respiratory tract (rhinitis, sinusitis), in which edema of the nasopharyngeal mucosa is observed. Hyperthermia (high fever in inflammatory processes in the body) also reduces the sensitivity of chemoreceptors.

Sensory food analysis

Although the structure of the taste analyzer is the same for all people, for some of us, due primarily to genetic features, it has a low threshold of sensitivity. As a result, there is an increased ability to distinguish more food colors and flavors. The taste analyzer, as well as the olfactory in such people, called tasters, can differentiate to taste and smell, for example, from 200 to 450 kinds of tea. Most of us use a taste sensory system primarily for analyzing the taste of food products, thus satisfying their need for fresh and quality food needed for the normal operation of the gastrointestinal tract.

The taste sensitivity of chemoreceptors can vary. So, it rises during pregnancy (symptoms of toxicosis), during lactation, under stress. Under normal conditions, the taste sensations can be enhanced, for example, by heating the food to 30-40 ° C. This technique is used in the process of assessing the taste of food and drinks. For example, wine and beer before the tasting is necessarily heated.

In this article, the structure and functions of the taste analyzer were considered. It also studied its role in perception and differentiation of environmental stimuli.