[Campbell Biology P.1121] A neuron's membrane potential shifts from -70 mV to -50 mV. Which o... | Practice Question

A neuron's membrane potential shifts from -70 mV to -50 mV. Which of the following changes in ion permeability would most likely cause this shift, and why?

  • A: Increased K+ permeability, because K+ ions would flow out, making the inside more negative.
  • B: Decreased Na+ permeability, because fewer Na+ ions would enter, making the inside less positive.
  • C: Increased Na+ permeability, because Na+ ions would flow in, making the inside more positive.
  • D: Increased Cl- permeability, because Cl- ions would flow in, making the inside more negative.

Explanation

A shift from -70 mV to -50 mV represents a depolarization the inside becomes less negative . This typically occurs due to an increase in permeability to ions like Na+, which have a positive charge and a higher concentration outside the cell. When Na+ channels open, Na+ flows into the cell, making the inside more positive less negative .