Which statement best describes receptor potentials and generator potentials and their relation to action potential generation?

Which statement best describes receptor potentials and generator potentials and their relation to action potential generation?

• A. Receptor potentials occur in sensory receptors; generator potentials occur in primary afferent neurons; both are all-or-none.
• B. Receptor potentials occur in sensory receptors; generator potentials occur in primary afferent neurons; both are graded depolarizations that may trigger action potentials if threshold is reached.
• C. Both potentials are all-or-none responses that do not vary with stimulus.
• D. Generator potentials occur in postsynaptic neurons after a chemical synapse.

Answer: (B)

The main idea is that sensory signals start as graded depolarizations rather than spikes. Receptor potentials occur in the sensory receptor cells themselves as they transduce a stimulus, and they are proportional to the stimulus strength. These receptor cells typically release neurotransmitter onto the attached primary afferent neuron, producing a generator potential in the peripheral end of that neuron. The generator potential, like the receptor potential, is a graded depolarization, and if it reaches the threshold of the first-order neuron, it triggers an action potential that travels toward the CNS. This describes why the best statement is that receptor potentials occur in sensory receptors; generator potentials occur in primary afferent neurons; both are graded depolarizations that may trigger action potentials if threshold is reached. The idea that these potentials are all-or-none is incorrect, since both are graded by stimulus strength, and generator potentials do not occur in postsynaptic neurons after a chemical synapse.

The main idea is that sensory signals start as graded depolarizations rather than spikes. Receptor potentials occur in the sensory receptor cells themselves as they transduce a stimulus, and they are proportional to the stimulus strength. These receptor cells typically release neurotransmitter onto the attached primary afferent neuron, producing a generator potential in the peripheral end of that neuron. The generator potential, like the receptor potential, is a graded depolarization, and if it reaches the threshold of the first-order neuron, it triggers an action potential that travels toward the CNS. This describes why the best statement is that receptor potentials occur in sensory receptors; generator potentials occur in primary afferent neurons; both are graded depolarizations that may trigger action potentials if threshold is reached. The idea that these potentials are all-or-none is incorrect, since both are graded by stimulus strength, and generator potentials do not occur in postsynaptic neurons after a chemical synapse.