Question

which of the following best defines graded potential?
sustained changes in membrane potential that occur in response to neurotransmitters.
large, all - or - none changes in membrane potential.
small, localized changes in membrane potential that vary in amplitude.
depolarization of the membrane potential caused by the opening of voltage - gated channels.
a rapid and brief change in membrane potential that travels along the axon.

Explanation:

Graded potentials are small, local changes in membrane potential. Their amplitude varies depending on the strength of the stimulus. They are not all - or - none like action potentials. Sustained changes in response to neurotransmitters is not the key defining feature. Large all - or - none changes refer to action potentials. Depolarization due to voltage - gated channels (in a large, all - or - none way) is also characteristic of action potentials. A rapid and brief change traveling along the axon is an action potential.

Answer:

Small, localized changes in membrane potential that vary in amplitude.