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9.1.1. The touch and the pain

The sense of touch and pain

The skin, in addition to having other important functions, is the one that contains the receptors for touch and pain, both on the outside and in the orifices (mouth, nose, eargenitals, etc.) and inside the body (digestive tract, organs, etc.). Pain receptors are the most abundant. In the skin, in addition to touch and pain receptors, there are other sensory receptors, such as those that capture pressure, cold or heat.

The skin is an organ with a protective function. It has three layers: epidermis, dermis, and hypodermis. The receivers are in the first two.

  • EpidermisIt is the outermost layer, made up of epithelial cells, which continually divide, replacing those that are lost. In it are the pain receptors, in addition to melanocytes (cells that produce melanin that darken the skin to protect us from ultraviolet radiation), and keratin, a substance with a protective function that waterproofs the skin and hair.
  • Derma. The inner layer is formed by connective tissuemuscle tissue, hair, glands, etc. Here the receptors for temperaturepressure and touch are located. In the dermis also grow hair in the hair follicle, sebaceous gland associated with arrector pili muscle and hair raising.
  • Hypodermis. It is made up of a layer of adipose tissue that acts as an insulator and a layer of connective tissue that joins the skin with adjacent organs and tissues.

There are several types of touch receptors:

  • Those that detect the pressure exerted by an object on our skin.
  • Those that detect the shape of the object.
  • Those that detect if we lose heat (sensation of cold) or if we gain it (sensation of heat).

The receivers of the pain may be associated with the touch. You have surely noticed that a slight pressure can end up causing pain, or a hot object can also cause pain. Feeling pain is a defense mechanism to get away from what is hurting us and avoid complications.

Touch receptors are nerve endings that may or may not be encapsulated.

  • The free nerve endings capture pressure, pain and temperature.
  • The corpuscles of Krause are slight vibrations and detect the cold.
  • The Meissner capture light pressure, continuous contact and textures .
  • The Ruffini corpuscles detect changes in pressure and temperature increase.
  • The corpuscles Pacinian respond to strong pressures and vibrations.

In the skin there are also the sweat glands, which in addition to participating in the excretory system , intervenes in the regulation of temperature.

Game: Parts of the skin.

Experiments with your body: The hands.

Experiments with your body: Sensitivity.

Experiments with your body: The sock.

Experiments with your body: The skin.

Answer in your notebook

9.2.- What stimuli can we detect through the skin?

Why do we get goose bumps?

Although it is not very cold, when we are afraid or excited, our skin bristles without our being able to control it. This is an inheritance from our hairiest ancestors. It is produced by the contraction of the small muscles that are at the root of each hair. 

When threatening situations occur, many mammals bristle to appear larger. This way, it may be possible to avoid an attack, since even the winner of the fight can end up with serious injuries.

When it is cold, by fluffing the hair, a layer of air is created that surrounds the skin that acts as an insulator, helping to keep warm.

For humans, who do not have that much hair, these functions are not useful to us, but they have remained as a reminder of the evolutionary past of our species.

Emotions only cause goose bumps in humans. It is caused by the adrenaline that we secrete in the face of fear, the fight, when we hear a very sad story, we watch a movie, that person you know caresses you ...