[Campbell Biology P.1124] Referencing the section 'Conduction of Action Potentials' and the '... | Practice Question

Referencing the section 'Conduction of Action Potentials' and the 'Why?' question at the end of the text, what mechanism primarily ensures that an action potential travels in only one direction along the axon, from the axon hillock towards the synaptic terminals?

  • A: The continuous opening of Na+ channels ahead of the action potential.
  • B: The active transport of ions by the Na+/K+ pump.
  • C: The refractory period of the membrane immediately behind the traveling zone of depolarization.
  • D: The all-or-none nature of the action potential ensures it only moves forward.

Explanation

The text states: 'An action potential that starts at the axon hillock moves along the axon only toward the synaptic terminals. Why? Immediately behind the traveling zone of depolarization, the... refractory period '. The refractory period, caused by inactivated Na+ channels, prevents the immediate re-excitation of the membrane segment that has just undergone an action potential, thus forcing the propagation in a forward direction.