Protopathic sensation is a type of sensory processing that is mediated by specialized nerve endings located in the skin, mucous membranes, and viscera (e.g., cardiovascular and gastrointestinal systems). It is considered to be the most primitive form of sensory processing and is primarily responsible for the perception of pain, temperature, itch, and tickle. Protopathic sensation is a key component of the body’s ability to detect and respond to noxious stimuli and is important for the maintenance of homeostasis.
The concept of protopathic sensation was first proposed by the German physiologist Johannes Evangelista Purkinje in 1837. He observed that humans and other animals responded to certain stimuli differently, depending on the area of the body that was stimulated. For example, a light touch to the skin was perceived differently than a light touch to the cornea. He concluded that different nerve endings were responsible for mediating the different responses to these stimuli.
The nerve endings responsible for protopathic sensation are classified as C-fibres and Aδ-fibres. C-fibres are thin, unmyelinated nerves that are responsible for the perception of pain, temperature, and itch. Aδ-fibres are slightly thicker, myelinated nerves that are responsible for the perception of tickle. Both C-fibres and Aδ-fibres are activated by mechanical, thermal, or chemical stimuli and transmit signals to the dorsal horn of the spinal cord, where the sensation is further processed.
In addition to its role in sensing noxious stimuli, protopathic sensation also plays a role in the perception of pleasure. For example, pleasurable sensations such as warmth, gentle massage, and mild tickling are mediated by C-fibres and Aδ-fibres. This suggests that protopathic sensation is important for the body’s ability to experience pleasure as well as pain.
Protopathic sensation is an important component of the body’s sensory system and plays a key role in the perception of noxious and pleasurable stimuli. A better understanding of this sensory system and its underlying mechanisms may lead to the development of more effective treatments for a variety of pain-related conditions.
References
Feldman, R. G., & Meyer, R. A. (2012). Sensory processing: An introduction to the neuroscience of the senses. Cambridge, MA: MIT Press.
Hsieh, J. C., & Terenius, L. (2013). Pain: A basic science perspective. Amsterdam: Elsevier.
Purkinje, J. E. (1837). Physiologische Untersuchungen über die Function der Nerven. Leipzig: Brockhaus.
Treede, R.-D., Aziz, Q., & Greenspan, J. D. (2015). Neuropathic pain: Mechanisms and management. New York, NY: Springer-Verlag.