The short-lived and localized changes in membrane potential are called graded potentials. A sensory receptor senses the stimulus. As the stimulus is sensed by the associated sensory neuron, there is the production of a graded potential. When the receptor of a sensory neuron is excited by some form of energy such as heat, light, etc., the resulting graded potential is called a generator potential. It is also called a receptor potential.
If the receptor potential is large enough to reach the threshold, it triggers one or more nerve impulses in the axon of the sensory neuron. For instance, thermosensory receptors sense the change in the temperature conditions and the associated sensory neurons generate the graded potential. Since the graded potential is generated due to temperature (heat), it is a generator potential.
