Which statement about generator potentials is accurate?

• A. Generator potentials occur in postsynaptic cortical dendrites.
• B. Generator potentials are all-or-none.
• C. Generator potentials occur at the axon hillock.
• D. Generator potentials are graded depolarizations in the first-order sensory neuron that may trigger an action potential.

Answer: (D)

Generator potentials are graded depolarizations produced by sensory transduction in the first-order sensory neuron (at the receptor ending or its cell body). Their size varies with stimulus strength, and they can summate over time or space. If the depolarization reaches the neuron’s threshold at the axon hillock, an action potential is fired; if not, no spike occurs. This explains why generator potentials may trigger an action potential but are not themselves all-or-none. They are not limited to postsynaptic cortical dendrites, and they are not all-or-none, nor do they occur at the axon hillock as the generator event. The accurate statement is that they are graded depolarizations in the first-order sensory neuron that may trigger an action potential.