Have you ever wondered how a human being perceives pain and temperature, what allows us to have this knowledge so relevant to our survival?
In this article we will talk about the somatosensory system, responsible not only for making us understand pain and temperature, but also of making useful the sense of touch, in addition, it takes care of the propiocepción: knowing the position in which our body is located.
- The somatosensory system is one of the most extensive systems of the human body Is it responsible for the treatment of all sensory information (e.
- G.
- Pain and temperature) of the body.
- Bones.
- Muscles.
- Viscera or skin.
- Because all its receptors are distributed throughout the body.
So there are two somatosensory systems
To understand how humans perceive pain and temperature, it is important to understand how skin receptors work, including the most sensitive receptors capable of generating sensations of pain.
The skin is the largest organ in the body and therefore the largest receptor. Through the skin, there are a lot of receptors grouped differently, which allows us to define the sensitivity or one of the four sensations that we receive through it: pressure, vibration (touch), pain and temperature.
Therefore, through the receptors of the somatosensory system of the skin, we receive information about the environment in the form of pressure, touch, pain, cold and heat.
The skin has a different sensitivity to pain and temperature, depending on the density of its receptors.
You could distinguish the skin with and without hair. Fur is the vast majority, but in the hairless region many more receptors are grouped, so it is more sensitive because there are more receptors on the skin.
The most sensitive sensory organs would be the lips, external genitalia and fingertips, as there is a higher density of receptors in these areas.
Although this is not entirely proven, hairy skin is thought to be more sensitive to vibration or touch as it causes hair to move.
Skin receptors fall into two categories: free nerve endings and encapsulated receptors.
Free nerve endings (NLTs) are nerve extensions that reach the skin and are probably the simplest sensory receptors, spread throughout the skin and are the most sensitive receptors to pain perception.
Although they also serve to understand everything, they specialize in pain. There is specificity, but not exclusivity.
The mechanism of transduction of the LNL is only the elongation of a specific part of them, which allows the opening of the sodium channels and, from there, the depolarization of the membrane, reaching the action potential. Produces cold by contraction and heat by expansion. .
Encapsulated receptors are a type of skin receptor, they are so called because they are covered by one capsule, there are those who speak of four types, others of five, these receptors are classified as follows:
They are found in lampiña skin and, to a lesser extent, in lampiñas skin, are densely grouped in lips, mammary glands and external genitalia, are especially sensitive to pressure, vibration and, to a lesser extent, pain and temperature.
They’re small encapsulated receptors. They have nerve endings, such as free nerve endings, surrounded only by connective tissue, are found on the skin with hairs and respond to low-frequency vibrations.
They are responsible for sensitivity to soft touch. They are found in hairless skin and are inserted into the dermal papillae.
Krause terminal bulbs are only found at the intersection of the mucosa with dry skin; their fibers are not myelinized and are extremely sensitive to pressure; its pressure activation threshold is the lowest in the entire human body.
Merkel’s records occupy a place similar to Meissner’s corpuscles in dermal taste buds, are they slowly adapted receptors and respond to a continuous change of stimuli, not directly?For example, the perception of temperature adaptation.
The perception of pain and temperature, in this case, is an adaptive alert system that allows us to avoid sources that cause harm, although it is a sensation that can be influenced by emotions, psychological, social, drugs, placebo, hypnosis?
It is therefore a very subjective emotion, suggesting that there must be neural mechanisms that modify or interfere with the transmission of pain, not only based on skin receptors.
Pain is divided into two types
Peripherally “where is the inevitable pain?” It has been noted that there is molecular information related to pain in the body.
In case of pain, some cells are damaged and secrete histamine and prostaglandin. The second, in itself, has no effect, unlike histamine, which causes the cell’s pain threshold to drop.
Prostaglandin makes damaged cells more sensitive to histamine and the pain threshold decreases further. There are pharmacological mechanisms to block histamine (antihistamines) and prostaglandin (acetylsalic acid).
At the central level, pain studies have focused on the thalamus, the pain is adaptive, but if it occurs with great intensity it can block the behavior, sometimes it is counterproductive and some wonder how we could not feel the pain, is it possible?How does the thalamus crash?
Pain inhibition is often called analgesia, influenced by emotional and physiological factors, however, in people who have suffered a stroke, it has been observed that lesions or blockage of the posterior ventral nucleus of the thalamus usually occur with loss of skin sensations, i. e. superficial. feelings of tact and pain.
Thus, wounds or blockage of the intralaminar nuclei eliminate deep pain, but not skin sensitivity. The dorsal nuclei are linked to the limbic system and usually interfere with the emotional components of pain, eliminating them.
The perception of temperature is relative, as we do not have receivers to perceive it absolutely. Can we only notice sudden changes in temperature?for example, place your hand in a container with very cold water and another with very hot water.
There are two types of receptors, one for cold and one for heat, which are distributed heterogeneously through the skin.
Cold receptors are closer to the epidermis, while heat receptors are in a deeper area. These are the same receivers, they only differ in their location.
Transduction into these receptors is caused by the deformation of the membrane or cone of the receptor by the effect of dilation or contraction of the skin, which causes the opening of the membrane and sodium channels.
If the receptors are grouped, the feeling of heat will be more intense, the associated nuclei by which it is difficult to perceive the cold and heat are intralaminar and, to a lesser extent, ventricular.
Therefore, it is extremely interesting to note that the perception of pain is due, among other things, to small receptors in the skin and an excellent affectation of the thalamus; Temperature too.
All these functions seem to have been developed motivated by the pursuit of our survival, and these tools we have are nothing more than a legacy of something our ancestors needed much more than we did.