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Touch is a sensation on the skin that results from active or passive contact between a person’s skin and an object.

The pressure applied to the skin is the main stimulus for the sense of touch. Another stimulus, the vibration, emerges when there is a rapid and regular change in pressure. Tactile perception is processed through the somatosensory system. This system is composed of sensory receptors, peripheral sensory neurons and brain cells.

When there is pressure on the skin, peripheral tactile receptors send information to the brain through the somatosensory pathway , which usually consists of three

Meanwhile, the somatosensory system in the spinal cord has ascending pathways that send information about the stimulus applied in the trunk of the body to the brain. In the brain, the tactile sensation is processed in the primary somatic sensory cortex, located in the postcentral gyre of the parietal lobe.

Sensitivity and tact

Anatomy of touch

The pressure, the physical stimulus for touch, can be measured by detecting the amount of indentation in the skin. Modern research on pressure sensitivity reveals that humans are less sensitive to pressure applied to and more sensitive to pressure applied to the face.

Another measurement for tactile pressure sensitivity is the two-point threshold. In this case, two physical stimuli of fine pressure are applied gently on the skin at the same time. Then, the person is asked to feel the physical stimuli and report if they are two points, or if he can only feel a stimulus.

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Fine touch and raw touch

There are two types of sensory modalities when it comes to tactile sensation. These are a fine or discriminatory touch, and a raw or non-discriminative touch.

The fine touch allows a person not only to feel the touch, but also to locate it. The location of touch through the modality of fine touch is possible thanks to the posterior route of the lemniscus of the medial column, which transports the information to the cerebral cortex.

On the other hand, the raw touch is a sensory modality that allows the person to feel the touch without having the ability to locate where the stimulus was applied. The spinothalamic tract is responsible for housing the fibers that transmit information about raw touch. The interruption of the fine tactile fibers can cause a person to locate the touch at the beginning, but can not do so later.

The skin

Anatomy of touch

The skin is composed of several layers. The upper layer is the epidermis and it is the layer of skin that you can see. The epidermis is water resistant and serves as a protective wrap for the underlying layers of the skin and the rest of the body. It contains melanin, which protects against the harmful rays of the sun and also gives color to the skin.

The epidermis also contains very sensitive cells called tactile receptors that give the brain a variety of information about the environment in which the body is located.

The second layer of skin is the dermis. It contains hair follicles, sweat glands, (fat), blood vessels, nerve endings and a variety of tactile receptors. Its main function is to support and support the epidermis by spreading nutrients to it and replacing the skin cells that are detached from the upper layer of the epidermis.

The lower layer is the subcutaneous tissue that is composed of fat and connective tissue. The layer of fat acts as an insulator and helps regulate body temperature. It also acts as a cushion to protect the underlying tissue. The connective tissue keeps the skin attached to the muscles and tendons below.

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Somatosensory system

The sense of touch is controlled by an enormous network of nerve endings and tactile receptors in the skin known as the somatosensory system. This system is responsible for all the sensations that we feel: cold, heat, softness, roughness, pressure, tingling,

  • Mechanoreceptors.
  • Termorreceptores.
  • Pain receptors and proprioceptors.

Mechanoreceptors

These perceive sensations such as pressure, vibrations and texture. There are four known types of mechanoreceptors whose only function is to perceive the indentions and vibrations of the skin: the Merkel discs, the corpuscles of Meissner, Ruffini and Pacini.

Termoreceptors

As the name implies, these receptors perceive sensations related to the temperature of objects. They are found in the dermis layer of the skin. There are two basic categories of thermoreceptors: cold and heat receptors.

They are found throughout the body, but cold receptors are found in higher density than heat receptors. The highest concentration of thermoreceptors can be found in the face and ears (hence the nose and

Pain receptors

Anatomy of touch

There are more than three million pain receptors throughout the body , which are found in the skin, muscles, bones, blood vessels and some organs. These receptors can detect pain that is caused by mechanical stimuli (cutting or scraping), thermal stimuli (burns) or chemical stimuli (poison from an ).

Although it is never fun to activate these pain-causing receptors, they play an important role in keeping the body safe from injury or serious damage by sending these early warning signals to the brain.

Proprioceptors

They detect the position of the different parts of the body in relation to each other and the surrounding environment. Proprioceptors are found in tendons, muscles and joint capsules. This location in the body allows these special cells to detect changes in muscle length and muscle

While many receptors have specific functions that help us perceive different tactile sensations, they are almost never just an active type at any given time.

Nervous signals: make sense of everything

Of course, none of the sensations felt by the somatosensory system would make any difference if they could not reach the brain. The nervous system of the body takes this important task. Neurons receive and transmit messages with other neurons so that messages can be sent to and from the brain. This allows the brain to communicate with the body.

References

Skin Sense Touch, Skin Anatomy, Home Science Tools,

Sense of touch: The perception of touch, NursinTimes,

Skin Senses: Touch, Explorable,

The Experience of Touch: Research Points to a Critical Role, The New York Times,

Anatomy of touch

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