Sense of Touch – Information, how it works, receivers

We explain what the sense of touch is, how it works and the anatomy that makes it possible. Also, your nerve receptors.

What is the sense of touch?

It is known as touch or sense of touch to one of the five senses through which the human being (and many other animals) can perceive the surrounding reality, specifically in terms of pressure, temperature, hardness and texture.

Of all the senses, it is perhaps one of the most complicated to study, since it does not have a specific organ that handles the information collected from the environment, but the nerve terminals responsible for it are distributed throughout our skin, that spreads throughout the body, and also inside our body.

The touch it is a passive and constant sense, whose influence is difficult to isolate from the rest of the senses and almost impossible to eliminate at any given moment. We are constantly perceiving our environment through touch, even if we do not notice it, and in this way we are constantly alert to any physical, chemical or thermal aggression that we may suffer: an alarm system that indicates when we are in danger.

But at the same time, touch can be a source of pleasant stimuli, and that is why plays an important role in socialization. Both in a kiss and a hug, as in a handshake or in sexual relations, touch is being an intermediary between our body and that of another person with whom we have developed a social and affective bond, which is a vital part of the imposing apparatus of society and culture.

In short, touch is a key sense for biological existence, which reveals to us our own three-dimensionality, that is, it keeps us continually aware of the space we occupy and the objects with which we interact.

How does the sense of touch work?

The touch It is the product of a complex network of nerve endings that run through our skin and our body, collecting sensory information regarding our external environment, but also inside our body.

Thanks to this we can feel the impact of external forces on our body, but also the sensations of pain, movement or internal discomfort, through which the body perceives itself.

This network of nerves is present between the epidermis and the dermis, and is made up of an immense army of different receptors, each one specialized in a certain type of stimuli and perceptions. In that way, tactile sensitivity encompasses three different types of perceptions, which reach the brain through different nerve pathways:

• Protopathic sensitivity. It is the most primitive and diffuse form of touch, making little or no difference between its stimuli, but at the same time it is the fastest to be perceived. Normally it deals with coarse or not very delicate stimuli, such as extreme heat or cold, pain and rough touch, which the subject cannot exactly locate in his body, but to which he reacts immediately.
• Epicritic sensitivity. It is a much more refined form of touch, localized, exact and with a high level of differentiation between stimuli, such as the ability to recognize shapes and sizes. Normally, to manifest itself, it must inhibit protopathic sensitivity to some extent.
• Thermoalgesic sensitivity. It is about the tactile sense linked to temperature (thermal sensitivity) and pain (algesic sensitivity).

In all three cases, the nerve stimuli are collected by their respective nerve endings and transmitted by different pathways (nerve conduits) to the brain, where they are processed and a reaction is generated. In this, the spinal cord plays a vital role in centralizing the different sensory stimuli.

Anatomy of touch

The skin is composed of several layers of tissue of different nature, and that play different roles in tactile perception. These layers are:

• The epidemic. It is the outermost layer of the skin, the one that we usually perceive with the naked eye, and that works as a protective, waterproof envelope for the rest of the layers of the human body. It is where melanin accumulates, a pigment that protects us from UV radiation and gives our skin its color, and it is also where the first touch receptors are found.
• The dermis. It is the deepest layer of the skin, which underlies the epidermis, and it contains abundant blood vessels, sebaceous and sweat glands, and the bulk of the touch receptors and their respective nerve endings. In addition, it is the layer in charge of replacing the dead cells of the epidermis.
• The subcutaneous tissue. Even deeper in our body are the tissues that go under the skin, made up of fats (which act as insulators and as cushions to protect internal tissues) and also connective tissues that hold all other tissues and organs together. . At this level are the deepest touch receptors, many of which are responsible for the internal perception of the body.

Nerve receptors

Nerve receptors in the skin can be of three types, depending on the tactile information to which they are sensitive and which they transmit to the central nervous system. Thus, we can talk about:

Thermoreceptors, responsible for perceiving variations in external temperature, as well as contact with cold or warm surfaces.

Nociceptors, responsible for producing pain, that is, capturing unpleasant or potentially harmful stimuli, and transmitting an alarm to the nervous system.

Mechanoreceptors, responsible for perceiving movement, pressure and other forms and forces in contact with the skin. They can be, in turn, of five different types:

• Pacini corpusclesResponsible for perceiving rapid vibrations and deep mechanical pressure, they are several millimeters long and are activated only at the beginning and end of the mechanical stimulus. They are especially numerous in the hands, feet, and sex organs, but also in connective tissue and many membranes.
• Ruffini corpuscles, responsible for perceiving and identifying the sensations of heat and the continuous or deep deformation of the skin, being especially sensitive to variations in said stimuli. They are small and abundant, and are found in the deep dermis and connective tissues, except on the surface of the skin on the dorsal aspect of the hands.
• Krause corpusclesSmaller and simpler than Pacini’s corpuscles, they are found in the deep dermis of the skin, but also in the submucosal tissues of the nose, eyes, mouth, genitals, and other similar regions. Formerly it was thought that they were concerned with perceiving the cold, but today it is unknown exactly what type of stimuli they register.
• Meissner corpuscles, responsible for the perception of soft touch, that is, of vibrations below 50 Hz, are receptors with very fast activity and enormous sensitivity, located in the superficial region of the dermis. Once activated, they show a margin of tolerance or decrease in activity in the face of continuous stimulation, which is why after a while we stop perceiving the clothes we are wearing, for example.
• Merkel Discs, also called tactile domes, are a set of mechanoreceptors found between the mucosa and the skin, dedicated to the perception of pressure and textures. They are some of the most acute and sensitive receptors in the skin, capable of obtaining very detailed information about their respective stimuli.

Taking care of the sense of touch

To take care of the sense of touch, it is precisely necessary to take care of the health of the skin and the mucous membranes of the body. This is done through considerations such as the following:

• Maintain regular skin hygiene and sensitive tissues, through bathing and drying, but avoiding the use of invasive, irritating or excessive chemicals.
• Protect the skin from dehydration by applying moisturizers or by drinking plenty of water, and protecting it from ultraviolet radiation using sunscreen or simply by controlling sun exposure.
• Do not expose the skin to chemicals, irritants, fuels or other reactions that can destroy or weaken the epidermis.
• Eat foods rich in vitamins A and D.