How Does The Body Perceive Pain And Temperature?

Have you ever wondered why you can feel pain? Or how do you know if something is cold or hot? How do people acquire this skill that is so important for survival? In this article we will talk about the somatosensory system, which is responsible not only for sensing pain and temperature, but also proprioception.

This is the body’s awareness of position, posture, movement, and so on. The somatosensory system is one of the largest systems in the body.

It processes sensory information (including pain and temperature) from the body and skin. The receptors are located throughout the body. There are two types of somatosensory systems:

• Cutaneous somatosensory system. Receptors in the skin make up this system. It’s an edge system. It has kinesthetic receptors that take in information related to body position and movement. The receptors are located near the joints and tendons.

• Organic somatosensory system. This system has receptors in the bones, muscles and intestines. It’s an internal system.

The cutaneous somatosensory system: the key to understanding perception

If you want to understand how people perceive pain and temperature, you have to understand how the sensory receptors work. The most sensitive sensory receptors are on the skin and can generate pain sensations.

The skin is the largest organ of the body. As a result, it is also the largest sensory receiver. There are many sensory receptors that are grouped in different ways all over the body. They determine the sensitivity to stimuli and each of the four sensations you perceive through the skin:

• Busy
• vibrations (touch)
• pain
• temperature

Is body hair relevant to pain and temperature?

There is a difference between skin with hair and skin without hair. Most of your skin on your body is covered with hair. The areas of your skin that don’t have hair actually contain a lot more receptors, making it more sensitive.

The most sensitive sensory organs are the lips, the external genitalia and the fingertips. Those parts of your body have the highest density of sensory receptors.

While no definitive studies prove this to be true, scientists believe that skin with hair is more sensitive to vibration and touch because both make hair move.

What kind of sensory receptors are there in the skin?

Cutaneous receptors are divided into two categories: receptors with free nerve endings and receptors with encapsulated nerve endings.

Free nerve endings

Free nerve endings (FNEs) are nerve fibers that terminate in the skin. They are probably the simplest sensory receptors. They are found all over the skin and are most sensitive to pain perception. Although they can also perceive other sensations, their specialty is pain perception.

The transduction mechanism of FNEs happens when a specific portion of the FNEs extends, allowing the sodium channels to open. This then leads to depolarization of the membrane, which creates an action potential. Contraction can therefore cause transduction at cold temperatures and dilation at warm temperatures.

Encapsulated nerve endings

Receptors with encapsulated nerve endings are a type of cutaneous sensory receptor. Their name speaks for itself: they are called encapsulated receptors because they are encapsulated. Some scientists divide them into four types, others, however, into five. They classify the receptors in the following way.

Pacini’s bodies: sensitive to pressure and touch

These receptors are most commonly found in hairless skin, although some are found in skin with hair. They are densely packed in the lips, mammary glands, and external genitalia. Pacinian corpuscles are especially sensitive to pressure, vibration and less sensitive to pain and temperature.

Corpses of Ruffini

These are small encapsulated receptors. Their nerve endings are similar to FNEs except they are surrounded by connective tissue. They sit in the skin with hair and react to low-frequency vibrations there.

Bodies of Meissner

These receptors are designed to detect a soft touch. They are found in hairless skin, specifically in the dermal papillae.

Corpses of Krausse

These corpuscles are found exclusively at the intersection of the mucosa and dry skin. Their fibers are not myelinated and they are extremely sensitive to pressure. They also have the lowest pressure threshold in the entire body.

Merkel’s Discs

Merkel’s discs are also located in the dermal papillae. They are slow-adapting receptors and only respond to a constant change in stimulus, such as temperature change.

Pain perception

So your body has an adaptive warning system that enables perception of pain and temperature. It helps you avoid things that could harm you, although emotional, psychological, and social factors also influence pain sensations. Things like drugs, placebos, and hypnosis can also affect the perception of pain.

As a result, pain is a highly subjective emotion. This suggests that there must be neural mechanisms that alter or disrupt pain transmission. This does not depend solely on cutaneous sensory receptors.

There are two types of pain:

• Avoidable pain. The best response here is to withdraw from the source that is causing the pain.
• Unavoidable pain exists at the peripheral and central level. As the name implies, this is the kind of pain you can’t escape.

In the case of unavoidable pain, scientists note that there is molecular information associated with the pain. When you feel pain, the damaged cells release histamine and prostaglandin. Histamine then ensures that the pain threshold of the cell goes down.

Prostaglandin makes the damaged cells more sensitive to histamine, which influences the pain threshold even more. This type of pain involves damaged tissue. However, there are medications that block the histamine (antihistamines) and prostaglandin (acetylsalicylic acid, also known as aspirin).

Can you block pain?

Studies point to the thalamus in centralized pain. While pain is adaptive, it can affect behavior if it is very intense. This can be counterproductive and some people also wonder about avoiding pain completely. However, can you somehow block the thalamus?

Usually we call pain suppression analgesia. Emotional and physiological factors influence the process. However, some stroke victims note that their injury or the blockage of the ventral posterior core of the thalamus tends to coincide with the loss of skin sensation. In other words, they lose superficial sensations such as touch and pain.

Similarly, injuries to the intralaminar nuclei block intense pain but otherwise do not affect skin sensation. Dorsomedial nuclei involve the limbic system and often interfere with the emotional components of pain.

Temperature perception

Temperature perception is relative because humans do not have sensory receptors that provide absolute information about temperature. You can therefore only observe sudden temperature changes. For example, consider moving your hand from very cold water to very hot water.

There are two types of receptors, one for cold and the other for heat. They are heterogeneously distributed over the skin. Cold receptors are located closer to the epidermis, while heat receptors are located in a deeper zone. They are the same kind of receptors. However, the difference is their location.

The deformation of the membrane or receptor electron due to dilation or contraction of the skin is what causes transduction. That deformation opens the membrane and sodium channels.

If the receptors are too close together, you feel 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.

So it is interesting that pain perception and temperature perception are due to small receptors in the skin and the participation of the thalamus. We conclude that all these functions seem to have evolved to allow humans to survive.