Sensitivity (we consider the concept in the framework of physiology) is one of the most important properties that both a person and any other living organism possess. Therefore, it requires detailed consideration. In the article we will present the types of sensitivity according to a number of classifications, as well as the types of its violations.
What is it?
All types of sensitivity in physiology are:
- Part of the reception perceived by the psyche. Reception is an afferent impulse entering the central nervous system.
- The ability of a living organism to perceive various irritations that come both from its own organs and tissues, and from the environment.
- The ability of an organism preceding a differentiated response to a stimulus is reactivity.
And now - the classification of types of sensitivity.
General sensitivity
Here several groups stand out at once - we will present their contents separately.
The exteroceptive type (surface sensitivity) within itself is divided into:
- tactile (gross);
- pain
- temperature (cold and thermal).
Proprioceptive type (deep sensitivity) - a feeling of yourself in space, the position of your body, limbs relative to each other. This species has within itself the following categories:
- a feeling of body weight, pressure;
- vibrational;
- feeling of touch (tactile lung);
- articular-muscular;
- kinesthesia (the so-called definition of the movement of skin folds).
Complex types of sensitivity:
- The feeling is two-dimensional - with it, we determine the place of contact with our body. It helps to know which symbol, number or letter is "written" on the skin with the finger of another person.
- Interoceptive - this sensitivity is caused by irritation of the internal organs.
- Discriminatory - helps to distinguish between touch, skin injections that are applied at close distances to each other.
- Stereognosis - this type of sensitivity helps to recognize this or that object by touch.
As for the given examples, their identification will be possible only upon further receipt and processing of the pulse from the primary cortical layer of the analyzer (it will be the central posterior gyrus) into associative or secondary cortical fields. The latter are mainly located in the parieto-postcentral zones, in the lower and upper parietal lobule.
We pass to the following classification.
General and special sensitivity
The same concepts are used here, only for a slightly different classification.
General sensitivity is divided into simple and complex.
Special sensitivity is represented by the following categories:
- visual;
- taste;
- olfactory;
- auditory.
Difficult sensitivity
In this classification, we consider various types of sensitivity - characteristic not only for humans, but for all living things in general.
This is the following:
- Vision - the perception of light by the body.
- Echolocation, hearing - the perception of living systems of sounds.
- Smell, taste, stereochemical feeling (characteristic of insects and hammerhead sharks) - the chemical sensitivity of the body.
- Magnetoreception - the ability of a living creature to feel a magnetic field, which allows you to navigate the terrain, determine the height, plan the movement of your own body. The type of sensitivity inherent in some sharks.
- Electroreception - the ability to sense the electrical signals of the world. Used to search for prey, orientation, various forms of biocommunication.
According to phylogenetic formation criteria
The classification was proposed by the scientist G. Head. There are two types of sensitivity of a person, a living being:
- Protopathic. A primitive form, having its own center in the thalamus. It cannot give an exact definition of the localization of the source of irritation - neither external nor inside the body. Reflects no longer objective states, but subjective processes. Protopathic sensitivity provides the perception of the most powerful, gross forms of stimuli, pain and temperature, which pose a danger to the body.
- Epicritical. Has a cortical center, is more differentiated, objectified. Phylogenetically considered younger than the first. Allows the body to perceive more subtle irritations, evaluate their degree, quality, localization, nature, and so on.
At the location of the receptors
This classification was proposed in 1906 by the English physiologist C. Sherrington. He proposed dividing all sensitivity into three categories:
- Exteroceptive. Here, the information is perceived by the body using the so-called exteroceptors that are located in the mucous membranes and skin integuments. This is a temperature, pain, tactile form of sensitivity.
- Proprioceptive. In this case, the information is perceived by proprioceptors. They are located in the tendons, muscles, labyrinth, joints, semicircular canals.
- Interoceptive. Here, irritation will be perceived by interceptors (they are called visceroceptors in a different way). They are found in vessels, internal organs, etc.
Varieties of skin sensitivity
Classical physiology distinguishes the following types of skin sensitivity:
- Pain. It arises under the influence of irritations destructive in their strength and nature. She will talk about direct danger to the body.
- Thermal (temperature) sensitivity. It allows us to determine what is hot, warm, cold, icy. Its greatest importance is for the reflex regulation of the body.
- Touch and pressure. These sensations are interconnected. Pressure, in fact, is a strong touch, so no special receptors stand out for it. Experience (with the participation of vision, muscle feeling) allows you to accurately localize the area affected by the stimulus.
In some classifications, the varieties of skin sensitivity will be divided as follows:
- Pain.
- Feeling of cold.
- Touch.
- Feeling of warmth.
Types of sensation thresholds
Now consider the classification of types of sensitivity thresholds:
- The absolute lower threshold of sensation. This is the smallest force or magnitude of the stimulus, at which its ability to induce nervous excitation in the analyzer is sufficient to cause a sensation.
- The absolute upper threshold of sensation. On the contrary, the maximum value, the strength of the stimulus, beyond which the body already ceases to perceive it.
- The threshold of discrimination (or the difference threshold of sensation) is the smallest difference in the intensity of two identical stimuli that a living organism can feel. Note that not every difference will be felt here. It is necessary that it reaches a certain size or strength.
Varieties of disorders
And now - types of sensitivity disorders. The following are highlighted here:
- Anesthesia is the name for the complete loss of any type of sensitivity. There is thermal (thermoanesthesia), tactile, pain (analgesia). There may be a loss of a sense of stereognosis, localization.
- Hypesthesia - the so-called decrease in sensitivity, a decrease in the intensity of certain sensations.
- Hyperesthesia is the opposite of the previous phenomenon. Here the patient has an increased sensitivity to certain irritants.
- Hyperpathy - cases of perversion of sensitivity. The quality of sensation changes - point irritations crumble, some qualitative differences between the stimuli in the patient disappear. The sensation is painted in pain tones, it can be purely unpleasant. The aftereffect is also diagnosed - the sensation continues to remain after the termination of the stimulus.
- Paresthesia - a person experiences any sensations without the presence of their irritants. For example, "crawling creeps", a sharp sensation - "as if thrown into a fever", burning, tingling, and so on.
- Polyesthesia - with such a violation, a single sensation will be perceived by the patient as multiple.
- Dysesthesia is a perverse perception of a certain irritation. For example, the touch feels like a blow, the effect of the cold - like the effect of heat.
- Synesthesia - a person will perceive the stimulus not only in the location of its direct impact, but also in a different zone.
- Alloheiria is a violation related to the previous one. The difference is that a person feels the effect of the stimulus, not in the location of his influence, but on a symmetrical section of the opposite part of the body.
- Thermalgia - cold, heat is perceived by the patient painfully.
- Dissociated sensitivity disorder is a case in which a certain sensation is disturbed, but all the others remain.
Types of Disorders
Types of sensory impairment can be divided into the following categories:
- Cortical type. This is a sensitivity disorder that will be observed on the opposite side of the body.
- Conductor type. The defeat of the pathways of sensitivity. Disorders will be detected down from the location of the lesion.
- Dissociated (segmental). It will be observed with damage to the sensitive nuclei of the cranial nerve of the brain trunks, as well as with damage to the sensitive apparatus related to the spinal cord.
- Distal (polyneuric) type. Multiple lesions affecting the peripheral nerves.
- Peripheral type. It is characterized by damage to the peripheral nerves and their plexuses. Here there is a disorder of all varieties of sensations.
Sensitivity is a fairly broad phenomenon in understanding. Evidence of this is the large number of classifications that within it subdivide it into multiple groups. Also today, a variety of types of sensitivity disorders has been established, the gradation of which is associated with the localization of the lesion, the manifestation of sensations in the patient.