Final answer:
Graded potentials are small, localized changes in membrane potential insufficient to cause an action potential but can lead to one if they summate and reach the required threshold. so, option D is the correct answer.
Step-by-step explanation:
In the context of neural communication, graded potentials are defined as small changes in membrane potential that by themselves are insufficient to trigger an action potential. These local changes are usually associated with the dendrites of a neuron and vary based on the size of the stimulus. For example, a slight change in temperature will cause a small graded potential, whereas a significant change results in a more substantial graded potential. Graded potentials can lead to depolarization, where the membrane potential becomes less negative, or hyperpolarization, making it more negative. These changes add together, or summate, and if the combined effect is sufficient, it can trigger an action potential, which is a rapid and significant change in membrane voltage.
Graded potentials are small changes in the membrane potential that are insufficient to trigger an action potential. They are local changes usually associated with the dendrites of a neuron. The size of the stimulus determines the amount of change in the membrane potential. For example, a slightly warm water would only initiate a small change in a thermoreceptor, whereas hot water would cause a large change in the membrane potential.