Transduction is the process by which a noxious stimulus is converted into an electrical signal by the peripheral pain receptor. When a harmful stimulus activates a nociceptor, ion channels open and generate a receptor potential; if this reaches threshold, an action potential is produced and travels toward the spinal cord. This conversion is the first step in how pain starts at the site of injury. It is separate from conduction, which is simply the propagation of that electrical signal along the afferent nerve toward the spinal cord. It is also distinct from perception, which is the brain’s interpretation and conscious awareness of the pain, and from modulation, which involves endogenous mechanisms that increase or decrease the signal as it travels. For example, heat activating nociceptor channels and producing a receptor potential illustrates transduction at work.