One of the most important functions of the nervous system is sensitivity. The brain sends and receives impulses from any contact of the organism with the external environment or as a result of the processes of internal work of the whole organism. All sensations are recognized by the brain and are included in the general conscious sensitivity of a person. Almost all parts of the body can perceive various kinds of irritations. And tactile sensitivity receptors are present not only in the superficial layers - skin, mucous membranes, but also in deep areas - muscles, ligaments, joints, tendons, bones.
Origin of the concept
The property of the nervous system to perceive external and internal irritating effects with the help of special cells (receptors) and respond to them is referred to a generalized concept - sensitivity. Moreover, it is characteristic of both man and animal. In turn, tactile sensitivity is a kind of susceptibilityskin cover. It is interconnected with the sensations of touch and response to stimuli, pressure, vibration. Tactile receptors are part of the tactile system. They are located on the mucous membranes and the surface of the skin.
The very concept of "tactile sensitivity" comes from the Latin tactilis - tactile, touch, tango - touch, touch - refers to a variety of sensations that occur after exposure to the skin of various mechanical stimuli (touch, squeezing, pressing, vibration, stroking, pinching, injections, touching objects, etc.).
Essence and specificity
Specialized receptor cells have a high selective susceptibility to various stimuli. Along with the main types: pain, muscular-articular, temperature, internal organs, there is tactile sensitivity. Human physiology allows you to receive data from sensory receptors that are on the skin, muscles, joints, and in the inner ear. Receive information about the outside world and form an idea of the body's position in space, surfaces and textures. The main and integral part of interpersonal communication is tactile sensitivity. It is she who plays an important role in physical intimacy.
In English there is a similar concept - tactile sensitivity. It also acts as a way of knowing the world around. Scientists have proven that touch is one of the first senses that arises in an embryo. The development of tactile sensitivity plays a paramount role ininfants, as children with tactile impairments have problems surviving even with the ability to hear and see.
Tactile receptors
The very concept of "receptor" means by itself the apparatus of the nervous system, capable of perceiving the actions of stimuli. Tactile sensitivity is carried out by two receptor systems:
- encapsulated nerve endings (Meissner bodies, Vater-Pacini bodies, Merkel discs);
- nerve plexuses around hair follicles.
These are sensitive points distributed throughout the body with varying degrees of density. Average indicators - 25 points per 1 square centimeter. In different parts of the body, the degree of density is different, respectively, the greater the density, the higher the severity of susceptibility. The surface of the tongue has the greatest degree of acuity of sensations, the sensitivity of the fingertips is still pronounced.
Primary types of sensations
After exposure to an irritating nature on the receptors, several types of sensations appear:
- Vibration.
- Touch.
- Tickling.
- Pressure.
Usually they are presented as different degrees of sensation of the same impact, since they occur in cases of deformation of the skin surface under the influence of mechanical stimuli.
Description of tactile sensitivity receptors
Our body is extremely interesting! ToFor example, each receptor is responsible for a specific response to external stimuli. There are encapsulated nerve endings (covered on the outside with a special capsule of connective tissue), they include:
- Meissner's bodies are located in the shallow layers of the skin. These are free endings of nerve fibers located near the smallest vessels, the thinnest nerve fibers around the hair follicle in those areas where hair is present. The largest number of this type of receptors are found on the surface of the palms, fingertips, feet, lip border, and tongue tip. These receptors help to perceive the outside world.
- Merkel's discs - located in small groups in the deep layers of the epidermis and mucosa. These receptors are responsible for the feeling of pressure. They give a reaction to the deflection of the skin under the action of mechanical stimulation, perceive tactile irritations that occur when the skin comes into contact with objects. Taurus are located on especially sensitive areas and are surrounded by the thinnest sensitive nerve endings.
- Lamellar bodies of Vater-Pacini respond to vibrational actions. They are found in the deeper layers of the dermis, adipose tissue, mucous membranes, on parts without hairline. They serve as detectors of short mechanical impacts. The sensation of vibration appears after irritation and deformation of several Vater-Pacini bodies.
Unencapsulated nerve endings are located on the surface of the skin, which convey the feeling of tickling and movement on the skin.
Localization of tactile sensations, measurement of sensitivity
A person determines the place of feeling touches or pressure very accurately. Localization is developed under the control of other organs of vision, muscular susceptibility and experience gained in the process of development.
Tactile sensitivity in different parts of the skin is distinguished by its sharpness. Lips, nose, tongue are characterized by a high degree of susceptibility compared to other parts of the body. Sensitivity is measured using a Frey esthesiometer. The device determines the pressure required to stimulate the receptors and produce sensations.
Threshold of space
Sometimes with an instant touch at once to several points located close to each other, one gets the impression of only one common touch. The smallest distance between these points, giving out the reaction of several touches, is called the threshold of space. It is measured using a Weber aesthesiometer, which is similar to a compass with a millimeter scale.
Depending on the area on the body, sensations of touch occur at different distances and have different values of the space threshold. The minimum values on the fingertips, tongue and lips, the maximum values prevail on the shoulder, hip, back. Thresholds depend on the branching of nerve fibers and the number of tactile receptors in a given area.
Departments of the tactile analyzer (TA)
Responsible for recognizing effects on the skinreceptors located on the surface of the body and mucous membranes, and form TA, consisting of two sections:
- Conductive - consisting of sensory nerve fibers coming from receptors in the spinal cord, visual tubercles and a network of neurons that activate the brain and control the reflex activity of the spinal cord.
- The brain section of the analyzer, represented by the posterior central gyrus, where similar sensations arise.
Various devices are used to check the state of he alth and tactile sensitivity of a person. The simplest of them is the Mochutkovsky taximeter. It consists of eight surfaces of different textures, starting from the first - perfectly smooth to the eighth with deep notches. With reduced sensitivity, a person can distinguish by roughness only a few of the roughest surfaces.
