In this chapter, the mechanism of pain, pain pathway from Oro-facial area and the physiological principle of pain have been discussed in detail. In order to understand the mode of action of local anesthesia, it is essential to understand the pain physiology. This chapter contains the essential details of pain physiology that may be needed for an understanding of the mechanism of local anesthesia. The endogenous analgesic system is an important modulator part for pain intensity and a major contributor to pain gate theory, all that has been discussed in a concise and precise way to give the complex information in a simple way to understand and remember.
Keywords: Endogenous pain killer system, Impulse generation, Pain fibers, Pain pathway, Pain physiology, Principle of pharmacology for pain management.