<prompt> The increase in the threshold of a receptor when a series of stimuli of subthreshold intensity are applied in succession is calledAdaptationAccomodationInitiationResistance  <response>: Accommodation - Slow rising subthreshold stimulus failing to produce action potential even when the normal threshold levels are reached. This occurs because of inactivation of voltage-gated Na channels. Adaptation- Persistent application of suprathreshold stimulus fails to generate repetitive firing. 