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Neurophysiology and Synapses · USMLE Step 1

What is the primary difference between a graded potential and an action potential in neurons?

  1. Graded potentials are all-or-nothing, action potentials vary with stimulus strength.
  2. Graded potentials are mediated by ligand-gated channels; action potentials by voltage-gated channels.
  3. Action potentials decay over time and space, graded potentials propagate without decrement.
  4. Action potentials occur only at dendrites, graded potentials only at axon hillock.
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Correct answer: Graded potentials are mediated by ligand-gated channels; action potentials by voltage-gated channels.

Graded potentials often result from ligand-gated channel activation (e.g., neurotransmitter binding) and vary with stimulus strength, while action potentials are all-or-none events mediated by voltage-gated channels and propagate without decrement.

Difficulty: Medium Question 19 of 28

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