Retrograde action potentials are prevented by:
a) leaky K+ diffusion out of the cell
b) absolute refractory period of voltage-gated Na+ channels
c) Na+/K+ ATPase
d) temporal summation of signals from dendrites
Explanation
Retrograde action potentials are prevented by the absolute refractory period of voltage-gated Na+ channels. Since recently opened Na+ channels cannot reopen, the action potential is prevented from traveling in a retrograde fashion. It can only progress anterograde down the axon. If you ever see retrograde conduction mentioned in a neuron question of the MCAT, you should be suspicious of a trap answer.
a) leaky K+ diffusion out of the cell, incorrect, K+ diffusion contributes to the resting potential and has little to do with the action potential.
b) absolute refractory period of voltage-gated Na+ channels, correct.
c) Na+/K+ ATPase, incorrect, The Na+/K+ ATPase helps establish the concentration gradient of Na+ and K+ in the neuron.
d) temporal summation of signals from dendrites, incorrect, Temporal summation of signals from dendrites contributes to action potentials and has nothing to do with anterograde signal conduction.
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