Most theories of learning begin with a stimulus. To provide a background to educational psychology we should review these input devices. Moreover, An introduction to Physiological Psychology would be the logical agent we should use for our review. Physiological psychology is a behavioral science. The behavioral significance of a stimulus depends on its capacity to produce a neural impulse.
Receptors convert environmental stimuli into neural impulses.
The conversion process is known as transduction. The receptor is a biological transducer. Receptors share certain features with neurons. Like neurons, they have a resting potential, they also depolarize when stimulated. The depolarization is know as a generator potential.