The activation of receptors and channels at afferent nociceptor Aδ and C fibre terminals leads to the generation of an action potential that travels up the spinal cord to the brain for conscious pain perception. Nociceptive pain occurs in 5 phases: 1) Transduction, 2) Conduction, 3) Transmission, 4) Modulation, 5) Perception. Transduction begins when peripheral terminals of nociceptive C fibers and A-delta (Aδ) fibers are depolarized by noxious mechanical, thermal, or chemical energy. Several neurotransmitters are involved in carrying the nociceptive message. However, glutamate and substance P (SP) are the main neurotransmitters associated with the sensation of pain. These receptors can be activated by intense mechanical stimuli, including overdistention or traction; ischemia; and endogenous compounds, including bradykinin, prostaglandins, hydrogen ions, and potassium ions. Activation of these receptors produces pain.