We explain what touch is, how it works and which organs it uses. We also explain its characteristics and possible diseases.
What is touch?
Touch is one of the human senses, shared with other higher animals. It allows us to perceive the qualities of objects and media, such as texture, pressure, temperature and hardness. It also allows us to feel certain stimuli that later become pleasure and pain.
Touch is a key sense and as vital as sight or hearing, but much less visible and more difficult to study. This is perhaps because it is a passive sense that we cannot use at willto the point that many times we do not even associate it with the specific sensations it allows us, such as cold or pain.
The term touch is also used as metaphor in interpersonal relationshipsto refer to empathetic, delicate or considered communication: “Saying things tactfully,” for example, means doing it in a good way, without hurting yourself.
See also: Speaking apparatus
How does touch work?
The touch is part of the sensory systemwhich is permanently active in humans.
It is a sense that would work even if we were deprived of the others.
Operates on the basis of the confluence of the nervous system and the skinour largest organ.
Use a significant and diverse number of receptors which they transmit to the parietal lobe of the brain, responsible for deciphering nervous stimuli and providing a response.
The touch too operates based on the internal sensations of the body: movement, pressure, pain, everything is recorded by the nervous system, which keeps us constantly alert about the state of our body.
Organs involved in touch
Touch is not confined to one main organ, as is sight or hearing. On the contrary, it isIt extends throughout our skin and our internal tissues.
The skin is extremely important for the body. First of all, it is a protective barrier that it isolates us and selectively communicates with the outsideOn the other hand, it keeps us constantly informed about the ambient temperature, the damage we suffer or the objects we trip over.
The skin It has sensitivity throughout its surface, but it concentrates its specialized receptors in some specific areas. For example, the tongue or fingertips are particularly sensitive. On the other hand, the genitals are the most sensitive area, since they are responsible for the pleasurable sensations of intercourse, necessary for reproduction.
The skin consists of several layers of specialized tissue which is constantly being renewed. Each has its own maintenance mechanisms. These layers are:
- Epidermis. The outer layer of the skin, where the pigments that give it its particular color (melanin) are found and where the pores that allow its lubrication and cooling (sweating) are located.
- Dermis. The middle layer is rich in nerve endings, blood vessels and two types of glands: sebaceous (responsible for secreting the sebum that lubricates the skin) and sweat glands (responsible for secreting the sweat that cools and cleans the skin). The hair follicles, from which the hairs emerge, are also located there.
- Hypodermis. The innermost layer, called subcutaneous tissue (“under the skin”), consists of a set of fatty tissues that fulfill the functions of reserve and defensive cells of the body.
The sense of touch is not located in the outer layers of the skin but in the middle, where the nerve receptors are found.
nerve receptors
The skin has different nerve receptors, each specialized in a type of sensation: touch, pressure and temperature.
- Mechanoreceptors. A series of specialized receptors that transmit the diverse variety of tactile sensations, whether coming from outside (exteroceptors, such as Meissner’s corpuscles, Merkel receptors, Krause’s corpuscles and Ruffini’s corpuscles) or from inside the body (interoceptors, such as Pacinian corpuscles and also Ruffini’s corpuscles).
- Thermoreceptors. Those receptors specialized in perceiving cold or heat in the environment.
- Nociceptors. Those receptors that perceive pain and transmit it to the brain as a feeling of urgency.
Each type of skin receptor transmits its nerve information to the brain through a specific type of nerve fiber.
Three types of sensations
The sensations perceived by touch are of three types and are transmitted to the brain through different pathways:
- Protopathic sensitivity. The most primitive and poorly differentiated, responds to the thickest and broadest sensations, such as pain, extreme cold or heat. It is the first to reappear after nerve injuries.
- Epicritic sensitivity. The finest, most localized and precise, allows us to appreciate low-intensity stimuli, allowing us to recognize shapes and sizes.
- Thermoalgesic sensitivity. Those that are linked to temperature and pain.
Pressure
Those responsible for recording the pressure on the skin are the Pacinian corpuscles.. They tend to accumulate in areas close to the joints, in deep tissues and in the breasts and genitals. They are thick, onion-shaped, and are very sensitive to vibration or variation. Its concentration on the face makes it particularly sensitive.
Temperature
Those in charge of record the temperature in the skin are the Ruffini corpuscles. They are located under the skin and are capable of reporting both increases and decreases in temperature.
The tongue is the organ where they accumulate the mostIn addition, they are responsible for initiating actions to combat cold or heat, such as sweating, shivering, or vasoconstriction or vasodilation.
Pain
Specialized pain receptors are called nociceptors.. They are widely distributed over the skin, emphasizing the most vulnerable areas, since their mission is to alert the body of the injuries suffered as quickly and focusedly as possible, to avoid the source of the pain.
Touch and the brain
The brain receives in each parietal lobe all the nerve emissions coming from the opposite side of the body. To do this It has two sensitive areascalled somatosensory areas (I and II) that occupy different portions of the brain.
These areas allow two types of perception:
- Conscious self-perception. The one we notice and actively differentiate.
- Unconscious self-perception. It is a passive perception, which registers the world around us or the pain in some situation.
Why is touch important?
Touch is fundamental to life. It constantly alerts us to the situation we find ourselves in.of the situation in our environment and gives us a danger signal in case we hurt ourselves: pain.
Without such stimuli, we could perform actions without knowing that we are hurting ourselves, or it would be much more difficult for us to determine certain bodily stimuli. In addition to offering us the pleasures associated with touch, this sense allows us to communicate with other human beingsthrough hugs, handshakes, etc.
Diseases that affect touch
Some common touch conditions are:
- HyperesthesiaExaggerated perception of tactile sensations, due to a perception disorder, which causes excessive reactions to the slightest stimulus.
- HypoesthesiaThe opposite of the above: a noticeable decrease in the ability to perceive tactile stimuli, making everything seem very dull or distant.
- Anesthesia. Total absence of tactile stimuli in any region of the body.
- Hyperalgesia. Excessive increase in the sensation of pain, making everything hurt more and responding disproportionately to the degree of damage inflicted.
- Hypoalgesia. The opposite: absence of pain perception, which prevents the individual from realizing in time the damage caused or received, or causing it to be perceived as less than it really is.