Final answer:
The statement 'A positive feedback cycle is the main force in the generation of graded potentials at receptor ends' is false. Graded potentials at receptor ends are not typically generated by positive feedback mechanisms; they are localized responses to stimuli. A positive feedback loop maintains and can amplify the direction of a stimulus, which is not the case for graded potentials.
Step-by-step explanation:
Graded potentials, such as generator potentials and receptor potentials, are changes in membrane potential that are localized and vary in magnitude. They can be depolarizations or hyperpolarizations, and they occur due to a sensory stimulus. A generator potential can directly generate an action potential if it is strong enough.
In contrast, a positive feedback loop refers to a process where the direction of the stimulus is maintained, possibly amplifying it. An example of a positive feedback mechanism would be in the process of blood clotting, where each clotting factor activates the next in the cascade. However, graded potentials are not typically generated by a positive feedback mechanism; they are usually localized responses to stimuli.