The nerve signals, generated and conducted by neurons are called action potential. It is a sudden and fast change that occurs in response to a stimulus, for transmitting signals to the target tissues. Not all stimuli can generate an action potential. A minimum threshold level is required for the electrical value to produce an impulse. Generally the value of a threshold potential is about -50 to -55 mV. If the value does not reach the threshold level, it is called subthreshold stimuli and it cannot produce any impulse. Suprathreshold