Final answer:
During the repolarization phase of the action potential, the positive feedback loop that was active during depolarization is 'turned off' because of the opening of voltage-gated K+ channels.
Step-by-step explanation:
The repolarization phase of the action potential occurs after the peak of depolarization. During this phase, the positive feedback loop that was active during depolarization is 'turned off' because of the opening of voltage-gated K+ channels. These channels allow K+ ions to leave the cell, restoring the negative charge inside the cell and bringing it back to its resting membrane potential. This turn off of the positive feedback loop is essential for establishing the proper polarity of the neuron.