Which statement correctly differentiates an action potential from a graded potential?

Which statement correctly differentiates an action potential from a graded potential?

• A. An action potential is relatively slow and diminishes with distance.
• B. Graded potentials are all-or-none.
• C. Action potentials require summation across many inputs.
• D. An action potential is an all-or-none, propagating signal; graded potentials are local and can summate.

Answer: (D)

The idea being tested is how two types of electrical signaling differ in size, spread, and how inputs are integrated. An action potential is all-or-none and propagating: once the threshold is reached, a full-sized signal is generated and it travels along the axon without losing amplitude as it moves. Graded potentials, by contrast, are local changes that vary in magnitude with the strength of the stimulus, decay with distance, and can summate over time or across different inputs to influence whether an action potential will be triggered. This combination—all-or-none and propagating for action potentials, versus local, variable, and summatable for graded potentials—is what best differentiates the two.

The idea being tested is how two types of electrical signaling differ in size, spread, and how inputs are integrated. An action potential is all-or-none and propagating: once the threshold is reached, a full-sized signal is generated and it travels along the axon without losing amplitude as it moves. Graded potentials, by contrast, are local changes that vary in magnitude with the strength of the stimulus, decay with distance, and can summate over time or across different inputs to influence whether an action potential will be triggered. This combination—all-or-none and propagating for action potentials, versus local, variable, and summatable for graded potentials—is what best differentiates the two.