The Body’s Ability To Perceive Pain And Temperature

Have you ever wondered how it is possible for you to perceive pain ? Or how do you know if objects are hot or cold? How have humans acquired this ability that is so important to our survival?

In this article, we will talk about the somatosensory system, which not only allows us to register pain and temperature, but is also responsible for proprioception, which makes the body aware of position, position, movement, etc.

The somatosensory system is one of the body’s largest systems. It processes sensory information (ie pain and temperature) from the soma (body) and the skin. The system’s receptors are distributed throughout the body.

There are two types of somatosensory systems:

• The cutaneous somatosensory system. This system is based on receptors in the skin. It is a peripheral system of kinesthetic receptors that gathers information that has to do with the body’s position and movement. These receptors are located near joints and tendons.

• The organic somatosensory system. This system has receptors in the bones, muscles and stomach. It is an internal system.

The cutaneous somatosensory system: the key to perceiving pain

If you want to know how people can perceive pain and temperature, you need to understand how cutaneous sensory receptors work. The most sensitive of these receptors are found in the skin and they can cause pain.

The skin is the body’s largest organ, and therefore it is also the area that has the most receptors. There are many sensory receptors that are coordinated in different ways around the body.

They determine the sensitivity to stimuli and the four sensations that can be experienced through the skin: pressure, vibration (touch), pain and temperature.

Does body hair matter?

There is a difference between skin with hair and skin without hair. Most of the skin on your body is covered with hair. The parts of the skin that lack hair actually have much more receptors, which makes it more sensitive.

The most sensitive sensory organs are the lips, the external genitalia and the fingertips. It is these body parts that have the greatest concentration of sensory receptors.

Although there are no definitive studies that confirm this, researchers believe that skin with hair is more sensitive to vibrations and touch, as these cause the hair to move.

What type of sensory receptors are there in the skin?

Cutaneous receptors can be divided into two groups: free nerve endings (FNE) and encapsulated nerve endings (sensory bodies).

Free nerve endings are nerve fibers that go out into the skin. They are probably the simplest sensory receptors. They are found everywhere in the skin and are the ones that are most sensitive to pain experiences.

Although they can also register other sensations, they are especially suitable for perceiving pain.

The transduction mechanism in the free nerve endings is activated when a certain part of the nerve end is stretched, which causes the sodium channels to open. This leads to membrane polarization, which creates an action potential.

Contraction can trigger transduction at cold temperatures and expansion at warm temperatures.

Encapsulated receptors

Encapsulated receptors are a type of cutaneous sensory receptors. The name speaks for itself; they are said to be encapsulated because they are surrounded by a capsule. Some researchers divide them into four groups, others into five.

They classify them as follows:

Pacini’s bodies: sensitive to pressure and touch

These receptors are found mainly in hairless skin, although they also occur in skin with hair. They are closely grouped in the lips, mammary glands and external genitalia.

Pacini’s bodies are particularly sensitive to pressure and vibration, and less sensitive to pain and temperature.

Ruffini bodies

These are small encapsulated receptors. Their nerve endings are similar to free nerve endings, except that connective tissue surrounds them. They are found in hair-covered skin and they respond to low-frequency vibration.

Meissner bodies

These receptors are designed to sense light touch. They are found in hairless skin and especially in dermal papillae.

Krause’s sensory bodies

Krause’s sensory bodies are found exclusively between mucous membranes and dry skin. Their nerve fibers are not myelinated and they are extremely sensitive to pressure. They have the lowest pressure threshold in the whole body.

Merkel’s records

Merkel’s discs are also located in the dermal papillae. These are receptors that adapt slowly and only respond to continuous stimulus changes, such as temperature changes.

The body’s way of perceiving pain

Your body has an adaptive warning system that allows it to perceive pain and temperatures. It helps you avoid things that can hurt you, even if emotional, psychological and social factors also affect pain experiences.

Even things like medications, placebo and hypnosis can affect the way you experience pain.

In other words, pain is a very subjective experience. This suggests that there must be neuronal mechanisms that modify or disrupt pain transmission and it is not solely due to cutaneous sensory receptors.

There are two types of pain:

• Avoidable pain. The most appropriate reaction is to withdraw from the source of the pain.
• Inevitable pain occurs at the peripheral and central levels. As the name suggests, it is a pain you can not avoid.

Regarding unavoidable pain, researchers have observed that there is molecular information linked to the pain. When you feel pain, the damaged cells secrete histamine and prostaglandin.

Histamine lowers the cell’s pain threshold. The prostaglandin makes the damaged cells more sensitive to the histamine, which further affects the pain threshold. This type of pain involves damaged tissues.

There are drugs that block histamine (antihistamines) and prostaglandin (acetylsalicylic acid, also known as aspirin).

Can you block pain?

Studies point to the thalamus when talking about centralized pain. Although the pain is adaptable, it can affect the behavior if it is very intense.

This can be counterproductive and some people wonder if it is possible to completely avoid pain. Can the thalamus be blocked in any way?

Pain relief is usually referred to as analgesia. Emotional and physiological factors affect this process.

However, it happens that people affected by stroke notice that their damage or blockage of the ventral posterior nucleus of the thalamus often coincides with a loss of cutaneous sensations.

In other words, they lose superficial sensations, such as touch and pain.

Similarly, damage to the intralaminar cores causes deep pains to be blocked, but they have no effect on cutaneous sensory sensations.

Dorsomedial nuclei refer to the limbic system and the emotional effects that pain normally causes.

The perception of temperature

Man’s perception of temperature is relative, because we do not have any sensory receptors that give us absolute information about temperatures. We can only perceive rapid changes in temperature.

An example of this is when you move your hand from very cold water to very hot water.

There are two types of receptors, one for cold and one for heat. They are heterogeneously distributed throughout the skin. The cold receptors are closer to the epidermis, while the heat receptors are further down the skin.

The receptors are of the same type, but they are located at different levels in the skin.

Deformation of membranes or receptors, due to enlargement or contraction of the skin, is what causes transduction. This deformation opens the membrane or sodium channels.

If the receptors are too close to each other, you experience the heat more intensely. The nuclei in the thalamus that make it difficult to perceive cold or heat are the intralaminar nuclei and the ventricular nuclei.

It is therefore interesting that our ability to perceive pain and temperature depends on small receptors in the skin in collaboration with the thalamus.

In conclusion, we can say that all these functions seem to have been developed to ensure human survival.