Compare and contrast action and graded potentials. Your answer should include a definition of each, types, characteristics, ionic basis, functions, and anything else necessary to answer the question.

Question

What will be an ideal response?

Answer 1

Action potentials are stereotyped changes in axon membrane potential that function in long-distance
communication between neurons and their target cells. Graded potentials are variable membrane potential
changes, usually in dendrites of multipolar neurons, that function in either short-distance communication or
changing the probability of an action potential.
Action potentials result from opening of voltage -regulated ion channels, which occurs at or above a threshold
voltage. Graded potentials are not regenerative and result from the opening of ion channels in response to
neurotransmitter or a specific stimulus such as sound or odor, in the case of sensory receptors.
The rising phase results from influx of sodium, and the falling phase from efflux of potassium. Other characteristics
include the after-hyperpolarization, all-or-none nature, conduction without decrement, independence of
amplitude and duration from stimulus strength, refractory period, faster velocity in larger diameter or in
myelinated axons. Graded potentials can be depolarizing, if the ion channel is a sodium channel, or hyperpolarizing
in the case of potassium or chloride channels. Depolarizations increase the probability that threshold voltage will
be attained and an action potential will result. Hyperpolarizations decrease the probability of a resulting action
potential. Amplitude and duration are proportional to stimulus intensity, and graded potentials are conducted with
decrement.