Information coming from the outside world is perceived by our senses. Thanks to their selective work, the human body is able to adequately respond to all changes in the environment. The end result of the functioning of the sense organs, namely hearing, vision, smell, taste, tactile sensitivity and the vestibular apparatus, is the emergence of sensations and recognition of stimuli.
The great Russian physiologist I. P. Pavlov established that the cortical centers of the brain take part in the formation of sensations, to which excitation comes from the receptors of nerve endings through the centripetal nerves. Systems consisting of sections of the cerebral cortex and pathways - nerves and receptors, he called analyzers, or sensory systems. The taste analyzer, the structure and functions of which are determined by its anatomical and morphological features, will be studied inthis article.
Mechanism of taste sensations
Virtually all the substances we use as food have a taste. In physiology, 4 basic tastes are distinguished: sweet, bitter, sour and s alty, the perception and differentiation of which is carried out by the taste analyzer. Taste can be explained as the perception of chemical molecules that make up food by receptors located in the oral cavity and on the tongue. To understand what function the taste analyzer performs, let us turn to the study of its structure. So, let's look at what this zone of our body looks like.
Departments of the taste analyzer
In our body there are special systems that are responsible for hearing, sight, smell, tactile senses. The taste analyzer, the structure and functions of which we are studying, consists of three parts. The first is called peripheral, or receptor. It directly perceives environmental stimuli, which cause weak currents in the nerve endings, which transform into bioelectric impulses.
They are transferred to the second section of the taste analyzer - conductor. It is represented by the afferent nerve. Through it, excitation enters the cortical part of the taste analyzer, which is a certain part of the brain, in which the formation of taste sensations occurs.
Features of the peripheral department
The taste analyzer, as mentioned earlier, consists of three parts. Let us consider in more detail the receptor, or peripheral section. He is representedchemoreceptors that perceive stimuli in the form of various chemical compounds, and recognizes them by strength, quality (modality) and intensity. Chemoreceptors are part of the taste buds, or bulbs, which are dotted with the oral cavity and tongue. The nerve endings that are sensitive to s alty taste are located at the tip of the tongue and along its edges, to bitter - at the root of the tongue, to sweet - at the tip, to sour - along 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 pore. Each chemoreceptor contains 40 to 50 villi. The substances that make up food contact and irritate them, as a result of which an irritation process occurs in the peripheral part of the taste sensory system, turning into excitation. As people age, the threshold of taste sensitivity rises, that is, the ability to recognize a variety of flavors fades away.
In animals, the sensitivity of the gustatory analyzer practically does not change with age, moreover, the connection between the gustatory and olfactory systems is much more pronounced in them. For example, in cats, taste buds (Jacobson's tubules) are also olfactory nerve endings, which contributes to a finer discrimination of food quality.
How the conductor part works
Continuing to study the sections of the taste analyzer, consider how nerve impulses from chemoreceptors can reach the brain. For this there isconductor part. It is represented by fibers of a single path. It includes several nerves: facial, glossopharyngeal, vagus and lingual. It is through them that nerve impulses enter the brain stem - the medulla oblongata and the bridge, and from them - to the visual tubercles (thalamus) and, finally, to the temporal lobe of the cerebral cortex.
Damage to the conductive part of the taste analyzer, for example, as a result of paresis of the facial nerve, leads to a partial loss of taste sensitivity. During surgical interventions, for example, during operations on the facial part of the skull, the conduction of nerve impulses along the nerves of a single pathway, especially the vagus and facial nerves, decreases, which also leads to a decrease in taste sensitivity.
Cortex of the gustatory sensory system
The cortical part of any of the existing analyzers is necessarily represented by the corresponding part of the central nervous system located in the cerebral cortex. It carries out the main functions of the taste analyzer - the perception and difference of taste sensations. Excitation along the centripetal nerves enters the temporal lobe of the cerebral cortex, where the final differentiation of the s alty, bitter, sweet and sour taste of food occurs.
The relationship between the structure and functions of the taste analyzer
All three departments of the taste sensory system are inextricably linked. Damage to any of these parts (receptor, conduction or cortical) ortheir connections with each other leads to the loss of the ability to perceive and distinguish between taste sensations. The anatomical structure of the taste analyzer determines the specificity of taste sensations that arise due to irritation of the chemoreceptors of the taste buds.
Appetite. How does it come about?
Emotional and physiological need for food intake and those positive sensations that arise before its consumption and in the process of eating are commonly called appetite. In addition to the organ of vision, taste and olfactory analyzers are involved in its formation.
The smell, the type of food and, of course, its taste are conditioned stimuli that cause the process of excitation in the nerve endings of the taste buds. It enters the digestive center located in the medulla oblongata, as well as the structures of the limbic system and the thalamus.
Taste recognition mechanism
As was established by physiologists, in the chemoreceptors of the tongue, excitation occurs as a result of food, olfactory and visual stimuli (taste, appearance and smell of food). The recognition of various types of taste (bitter, sweet, sour, s alty) and their shades is carried out thanks to the analytical and synthetic activity of the higher part of the brain - the cerebral cortex. In her temporal lobe is the taste center.
Various pathologies and injuries that the taste analyzer undergoes lead to ageusia - partial or complete loss of taste sensations. It can also occur in a he althy personas a result of viral diseases of the upper respiratory tract (rhinitis, sinusitis), in which swelling of the nasopharyngeal mucosa is observed. Hyperthermia (high temperature during 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 characteristics, it has a low threshold of sensitivity. As a result, there is an increased ability to distinguish more food shades and flavors. The taste analyzer, as well as the olfactory analyzer in such people, called tasters, can differentiate by taste and smell, for example, from 200 to 450 types of tea. Most of us use the taste sensory system primarily to analyze the taste of food, thus satisfying our need for fresh and high-quality food, which is necessary for the normal functioning of the gastrointestinal tract.
The taste sensitivity of chemoreceptors can change. So, it rises during pregnancy (symptoms of toxicosis), during breastfeeding, in a state of stress. Under normal conditions, taste sensations can be enhanced, for example, by heating food to 30-40 ° C. This technique is used in the process of evaluating the taste of food and drinks. For example, wine and beer must be warmed up before tasting.
In this article, the structure and functions of the taste analyzer were considered. Its role in the perception anddifferentiation of environmental stimuli.
