Final answer:
The amplitude of the receptor potential is a function of the stimulus intensity, with greater stimulus leading to a larger graded potential but not affecting the size of 'all or none' action potentials which remain constant in amplitude.
Step-by-step explanation:
The amplitude of the receptor potential is a function of stimulus intensity. To understand this, consider the mechanoreceptor, which responds to physical pressure. The gated ion channels in the sensory neuron's plasma membrane open in response to a stimulus, altering the neuron's membrane potential. These changes in potential are graded potentials, meaning their magnitude varies with the strength of the stimulus. However, once the threshold is reached, an action potential is fired which is 'all or none' and does not vary in size with stimulus intensity. It is the frequency and number of action potentials, rather than their amplitude, that communicates the intensity of the stimulus to the central nervous system (CNS).