"A refractory period occurs following all types of potentials." Is this statemen

False. The refractory period occurs after action potentials and is a distinguishing characteristic, and results from properties of the voltage-gated sodium channels. Graded potentials do not involve channels that have refractory periods. Two stimuli that reach a dendrite at nearly the same time will increase the graded potential produced, whereas if two suprathreshold depolarizations reach the trigger zone at nearly the same time, the first will cause an action potential and the second will be ignored, because of the refractory period.